• TABLE OF CONTENTS
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 Front Cover
 Title Page
 Morpho-physiological characterization...
 Strategies at ciat for increasing...
 The role of architecture, crop...
 Horitabilities and phenotypic correlations...
 Early generation selection for...
 Yield system analysis for improving...
 Yield potential of climbing...














Title: Symposium on breeding for higher yield in beans
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Title: Symposium on breeding for higher yield in beans
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Publication Date: March 31, 1987
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Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Morpho-physiological characterization of early genotypes in common beans
        Page A-1
        Page A-2
        Page A-3
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        Page A-25
        Page A-26
        Page A-27
        Page A-28
        Page A-29
        Page A-30
    Strategies at ciat for increasing yield potential of common beans - finishing the domestication process
        Page B-1
        Page B-2
        Page B-3
        Page B-4
        Page B-5
        Page B-6
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        Page B-29
        Page B-30
        Page B-31
        Page B-32
        Page B-33
        Page B-34
    The role of architecture, crop physiology and recurrent selection in ideotype breeding for yield in dry beans
        Page C-1
        Page C-2
        Page C-3
        Page C-4
        Page C-5
        Page C-6
        Page C-7
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        Page C-14
        Page C-15
        Page C-16
        Page C-17
        Page C-18
        Page C-19
    Horitabilities and phenotypic correlations for seed yield and yield components of bean populations derived from crosses between determinate and indeterminate genotypes
        Page D-1
        Page D-2
        Page D-3
        Page D-4
        Page D-5
        Page D-6
        Page D-7
        Page D-8
        Page D-9
        Page D-10
        Page D-11
        Page D-12
        Page D-13
    Early generation selection for high yield in beans using physiological components of yield as selection criteria
        Page E-1
        Page E-2
        Page E-3
        Page E-4
        Page E-5
        Page E-6
        Page E-7
        Page E-8
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        Page E-11
        Page E-12
        Page E-13
        Page E-14
        Page E-15
        Page E-16
        Page E-17
        Page E-18
        Page E-19
    Yield system analysis for improving efficiency of breeding for higher yield
        Page F-1
        Page F-2
        Page F-3
        Page F-4
        Page F-5
        Page F-6
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    Yield potential of climbing beans
        Page G-1
        Page G-2
        Page G-3
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Full Text


XXX III REUNION
GUATEMALA, C.A.

MAR10 30
ABRIL 4 4
1987


Symposium c
H ihe ,' .


SYM. iS -.
^ **.- A


n Breeding for
in Common Beane :


. ..' I
,.%&^ ^ 1


CMIA\1T


CENTRO INTERNATIONAL DE
AGRICULTURE TROPICAL


THE BEAN/COWPEA
CRSP


INSTITUTE DE CIENCIA Y
TECNOLOGIA AGRICOLAS


574, 05c


i::
: si






XXXIII ANNUAL MEETING
PCCMCA



















SYMPOSIUM ON BREEDING FOR
HIGHER YIELD IN BEANS








March 31, 1987
Guatemala City, Guatemala


INSTITUTE DE CIENCIA Y
TECNOLOGIA AGRICOLAS


CENTRO INTERNATIONAL DE
AGRICULTURE TROPICAL


BEAN COWPEA COLLABORATIVE
RESEARCH SUPPORT PROGRAM










MORPHO-PHYSIOLOGICAL CHARACTERIZATION OF EARLY GENOTYPES
IN COMMON BEANS (Phaseol us vuliaris L.)


Rafael Rail RodriQuez**
Salvador Miranda Colin**
Stephen E. Beebe***






SYNOPSIS


The present study was carried out with the object of characterizing the
most important morpho-physiological traits and identifying archetypes
associated with higher yield in a group of early genotypes of common beans
(Phaseolus vulgaris L.) from Central America, Mexico, and Colombia.


Results obtained led to the conclusion that: (1) yield and physiological
maturity are highly and positively correlated with size parametaerc-
(2) early materials tend to be more efficient than late ones in their
utilization of leaf area; (3) to obtain higher yields, a strong, erect
stem, with few branches is desirable in early genotypes, as well as an
early-flowering and longer maturing genotype.












This work forms part of the thesis with which the main author obtained
his Master of Science degree, Centro de Genftica, Colegio de
Posgraduados, Chapingo, Mexico.
** Student and Professor-Scientist, respectively, Centro de Genetica,
Colegio de Posgraduados, Chapingo, 'Mixico.
*** Breeder, Bean Program, Breeding I, Centro Internacional de Agricultura
Tropical (CIAT), Call, Colombia.










INTRODUCTION


Improvement of earliness, in common beans (Phas~e~_lu vulgaris L.), has
always been impaired by the fact that this characteristic has not been
sufficiently characterized quantitatively. There is some knowledge as to
its inheritance, but no numeric data are available on the characteristics
of possible early progenitors which both offer earliness as a mechanism to
escape adverse factors and at the same time sustain yields. Furthermore,
the dynamics of growth in early genotypes is not well known; this knowledge
could better orient a breeding program to recombine earliness and yield.


Due to risk of irregular rainfall distribution, many farmers prefer
short-cycle bean varieties, with which the crop is exposed in the field
during a shorter period, and therefore, has fewer risks.


However, earliness imposes certain limitations on the biological capacity
of the crop. A short cycle limits total photosynthesis and, to a certain
degree, yield potential. Additionally, a reduction in the total biomass of
the plant is observed, resulting in a smaller number of floral buds and
reduced yield.


The present study was conducted with the object of characterizing a group
of early genotypes from Central America, Mexico and Colombia, that could
serve as outstanding progenitors in a breeding program for earliness and
high yield in common beans, as well as to identify some characteristics
related with higher yields.


The suggested working hypotheses were:


a. Smaller size parameters in early genotypes are related with lower
yields;
b. Early genotypes are more efficient than late ones, since they require
less structural material (smaller size);










c. A main strong, erect stem having few branches, is associated with
higher yield in early genotypes; and,
d. Late-flowering and early-maturing early genotypes have higher yields.


REVISION OF LITERATURE


Buttery and Buzzel (1972) point out that the search for high yields has
stimulated the interest in the physiological factors contributing to yield.


To increase yield in beans it has been suggested to identify the limiting
factors under favorable conditions and determine the characteristics
related with productivity (Tanaka and Fujita, 1979; Charles-Edwards, 1982),
as well as the most appropriate combination of variety, environment, and
agronomic practices (Yoshida, 1972); the genetic, physiological, and
environmental factors capable of influencing production must be considered
simultaneously (Wallace and Munger, 1966; Charles-Edwards, 1982).


Yoshida (1972) points out that the vegetative growth, the formation of
storage organs, and seed filling must be studied in order to obtain higher
yields. On the other hand Poey (1978) considers, with this same objective,
the need to study the vegetative cycle, plant architecture, and leaf area.


Mendoza and Ortiz (1973) point out that seed yield must not be the main
criterion of selection; criteria regarding seed production efficiency must
be introduced.


Laing (1977) and Bauer (1969) emphasize the need for early maturing bean
varieties with the object of avoiding dry periods.


Although it has been confirmed that late bean varieties yield more than
early varieties, the farmer prefers the latter in which case he has less
risk (Leiva, 1977; Garcia, 1985).










According to Donald (1968), to date two groups can be considered in terms
of the philosophy of the breeding programs to increase yield:


a. Where the purpose is to remedy some known defects in the crop or
"elimination of defects" and,
b. Where the basic objective is "selection by yield" without considering
the reason or the cause of the yield obtained. A valuable additional
option would be improvement by archetypes.


The improvement of archetypes implies the definition of both the
environment for production, and the morpho-physiological characteristics of
the archetype (Mock and Pearce, 1975); improvement of plant structure
(Adams, 1973); and changes in agronomic practices (Donald, 1968).


An erect, strong stem with few branches (2-4 branches forming upwards acute
angles with the stem), are attributes of a high-yielding bean archetype
(Laing, 1977; Davis and Evans, 1977; Stofella et al., 1979; Adams, 1973,
1981; Izquierdo and Hosfield, 1983).


MATERIALS AND METHODS


The present study was carried out at the CIAT-Palmira station of the Centro
International de Agricultura Tropical, CIAT, Colombia.


The Station is located at 3"30' latitude North, 7622' 22" longitude West,
and 965 masl; it has a mean annual temperature of 23.9C and a mean annual
rainfall of 938 mm.


Two experiments were conducted: the first (EA) was planted on June 28,
1985 and the second (EB) on September 19, 1985. The experimental plot was
composed of nine rows 6.0 long, with 0.6 m between rows. Subplots were
located within this plot where growth, yield, and its components were
measured. The eight samples for the growth analysis had 1.0 linear m (0.6










m2), adjusting the data later to 1.0 m2. For yield, the net plot had five
2.0 m rows, with 0.6 m between rows. Yield components were measured on 1.2
m2 plots.


Sixteen bean (Phaseolus vulgaris L.) genotypes supplied by the CIAT Bean
Program were used, of which 12 presented diverse degrees of earliness; the
remaining four were used as late controls. The characteristics of the
materials are shown in Table 1.


Crop management recommendations of the Program were used.


The data collected was divided into three classes: data of growth
analysis, development data, and yield data and its components.


Eight samplings were done for the growth analysis. The first, which was
common to all genotypes, was done 12 days after planting; on the other
hand, the last sampling was made to coincide as much as possible with the
physiological maturity of each genotype. Samples were taken at random as
to their location within a total plot. Subsequently they were dried during
72 hours at 65C to arrive at a constant weight. Leaf area was measured
with an automatic Hayashi Denkoh apparatus, manufactured in Japan, model
AAC-200. The Functional Approximation was used.


Developmental data were taken from the yield subplot. To determine yield
and its components, each subplot was measured at random.


In all cases, results were subjected to analysis of variance and then to a
comparison of means by Duncan's method (5%); at the'same time linear
correlations were established among all the variables of interest, both
considering all genotypes (n = 16) and eliminating the late group (n = 12).











RESULTS AND DISCUSSION


Overall, in most of the variables studied, the tendencies were similar in
the two experiments, although their values were greater in experiment B
(EB).


Size Parameters


In general, it has been observed in everyday work, that reduced parameters
of size are found to be correlated with low yields in early materials.
Tables 3 and 4 give the basic information with respect to some variables
related with plant size.


In Table 5, size variables considered important have been grouped together,
based on preliminary analyses. In both planting periods these variables
are consistently associated with yield. Although correlations are positive
in all cases, there is absence of significance for total nodes to maturity
and maximum height. An analogous relationship exists between the size
variables and days to physiologic maturity. Considering the early group (n
= 12), tendencies seem to be less marked (Table 5). Therefore, results
suggest an overall close and positive association among parameters of size,
physiological maturity, and yield.


Within the group of early genotypes and for most of the size parameters,
there are two genotypes which always stand out among that group; these are
JU-84-7 and Rojo de Seda. Both consistently present the highest values for
the size parameters, and have intermediate earliness; these two genotypes
could be used as progenitors which deviate from the general tendencies
already mentioned (Tables 3, 4, and 8).










Efficiency parameters


Efficiency, understood as the greatest gain at the lowest possible cost, is
a characteristic which is expected to be maximized in early genotypes, as
compensation for the lov size parameters of these
genotypes.


Tables 3 and 4 show the basic values for efficiency variables during the
two periods studied.


Considering dry matter production per unit of surface and time (Crop Growth
Rate, CGR), consistently the most outstanding genotypes within the early
group are Rabia de Gato, Rojo de Seda, and JU-84-7 for the two periods.
This is important because CGR is directly related to total dry weight,
which is associated with yield (Mesquita, 1973; Mosjidis, 1975) and has
also been suggested as an acceptable selection parameter for'high yield in
beans (Wallace, 1973; Masaya, 1985).


Table 4 shows that the highest CGR value was 16.4 g/m2/day corresponding to
JU-84-7, 30 days after emergence. This figure is very similar to the
highest CGR value obtained for soybean (Buttery, 1970), which was
17.2g/m2/day, and highlights the importance of JU-84-7 since this genotype
combined earliness and high CGR.


Efficiency of a plant in increasing its dry weight from its already
existing weight is important, especially during the first stages of growth.
Such efficiency, plus good initial agronomic management of the crop will
insure good growth during the first stages of the vegetative cycle, which
is important for plant establishment. Efficiency in this respect is
referred to as Relative Growth Rate (RGR).


In experiment A (EA), JU-84-7 was observed to be a very efficient genotype
in its RGR (Table 3), surpassed only by ICTA-Quetzal. In experiment B (EB)











JU-84-7 again shows the highest RGR value -- a marked difference with
respect to the total group of genotypes (Table 4).


CGR and RGR are positively associated with yield, either considering all
the materials or only the early ones, and especially in EA (Table 6).


It is likely that prevailing climatic conditions which were contrasting for
the two periods were the cause motivating a close association of these
rates with maturity in EA and a null association in EB; favorable
conditions resulted in exuberant growth of all genotypes in EB. Any
advantage that the late genotypes might have had was lost due to
inefficient use of excessive leaf area.


The efficiency of the leaf area of a plant can be described by the Net
Assimilation Rate (NAR), which is closely linked to the Leaf Area Index
(LAI). When the LAI passes a value of 4.0, considered by Laing et al.
(1983) as optimal, its efficiency declines due shading of leaves in the
lower part of the canopy. This reduced efficiency will be reflected in
lower values of NAR.


In EA, no genotype attained the optimal value of maximum LAI (MAXLAI),
while in EB many genotypes attained it and several exceeded it, especially
the later genotypes. This fact is manifested in lower values of NAR in the
late genotypes compared to EA (Table 4). NAR had a low and positive
association, although not significant, with maturity and yield in EA
(Table 6). But in EB such association became negative and highly
significant for maturity and of smaller magnitude for yield.


These observations on MAXLAI and NAR explain many of the differences
observed between EA and EB. For example, in EA there were significant
differences between genotypes for the parameters Maximum Total Dry Weight
and Yield/Day, but these disappeared in EB (Table 7). Apparently the late
genotypes lost much of their advantage in EB and the early.genotypes almost











equalled the late materials in these parameters. It appears that the late
genotypes arrived at a sort of "ceiling" in EB, since these did not
demonstrate a proportional improvement compared to the early materials in
passing from EA to EB. The MAXLAI no doubt is an important part of this
ceiling.


On the other hand, since NAR is a "net" rate, respiration is also involved
(Williams et al., 1965; Wallace and Munger, 1965); this should be taken
into account in interpreting fluctuations in the NAR as observed between EA
and EB, nevertheless, the relationship of respiration to LAI and other
parameters measured is not known.


Among the early group in EA, JU-84-7 was the most outstanding in terms of
yield and had a high NAR (Tables 3 and 8). In addition to JU-B4-7,
genotypes 6 3017 and Rabia de Gato show in EB a good combination of yield,
NAR and earliness (Tables 4 and 8). The contradictory NAR responses
obtained in the two periods do not permit firm conclusions as to a pattern
of response for early bean genotypes.


Yield/Day presented a significant association with maturity (r = 0.58 +)
only in EA (Table 6); in EB, this relationship is inverted (r2 = -0.48)
within the early group. It is likely that in EB. the greater leaf area
(LA) of the early genotypes may have influences the increases in yield and
that on the contrary, in the late genotypes, this greater LA was not used
as efficiently for yield increase as it was by the early genotypes.


Additionally, Yield/Day is a good parameter of efficiency to quantify final
yield, when comparing genotypes of different biological cycle. For
example, if yield per se is analyzed in experiment B, significant
statistical differences are found; but if Yield/Day is calculated, the
analysis shows that on this basis, all genotypes are statistically equal
(Table 7 and Figure 1).











Within the early group in EA the most outstanding genotype in terms of
Yield/Day is JU-84-7, and in EB, JU-84-7 and G 3017; the latter has the
advantage of being an earlier material although its yields are slightly
lower (Table 8).


In cereals, due to their low degree of defoliation, the harvest index (HI)
is a good yield selection criterion. Instead in legumes such as beans,
defoliation could affect the relationship between HI and yield. This
suggests that the poor environmental conditions (experiment A) could cause
rapid defoliation of the plant and thus an erratic HI, especially under the
conditions of the present study, where a broad range of maturities were
involved (Table 8). Under good environmental conditions (experiment B),
the HI seems to function better, and comparatively high HI were detected in
early genotypes (Table 8).


Overall, no consistency was found in the use of the HI as a criterion for
selection for high yield in early genotypes (Table 6). It is possible that
in considering total dry matter production, including that which could have
fallen during the biologic cycle (folioles, petioles, and roots), the HI
would be more effective in identifying the best-yielding early genotypes.


Archetype A. A plant type whose characteristics would be compatible with
early maturity was proposed. -It was hypothesized that a high-yielding
plant of reasonable earliness, would be that with a strong, erect primary
stem, and few branches. This coincides with most bean archetypes described
in the literature, although a more detailed description is not done in this
research.


Data obtained for the variables under study appear in Tables 9, 10, and 11.
Results of the variance analysis are found in Table 12.


As shown in Tables 9 and 10, the highest-yielding early genotypes for the
two periods are JU-84-7, G 3017, and Rabia de Gato. These .three genotypes











are representative of the range of plant height of the early group
(Table 11). If the Maximum Length (MAXLEN) variable is considered, it is
found that the difference between MAXLEN and the height of G 3017 and Rabia
de Gato is not sufficient to result in a prostrate habit in the case of EA.
As to JU-84-7 in EA and the three genotypes in EB, the differences are more
marked. In any case, the excess length in the main stem did not induce
lodging.


With this in mind, the distribution of seed dry weight in the main stem
(SDWS) and in the branches (SDWB) shows the same tendency in the three
cases mentioned, that is, that SDWS is twice SDWB (Table 11); this suggests
that moderate plant ramification is conducive to higher yields (Tanaka and
Fujita, 1979).


The three genotypes developed a strong, erect stem with few branches, and
thus it appears that the latter were not the determinants of greater seed
production. Limited ramification of these genotypes reduced the total
number of nodes. This could cause yield reduction due to fewer pods if
the nodes are considered to be potential productive points but such
reduction in pod set was not observed (Tables 9 and 10). Thus, total
number of nodes was not a limitation to yield in this case.


Information in the literature reviewed indicates that bean archetypes
should have 2-4 branches; this coincides with the limited ramification of
the three early genotypes and of the high yield levels found in this study.
This plant structure probably enables greater diffusion of light, air, and
CD2 within the strata of the leaf mass.


Archetype B. Assuming that the time elapsed until flowering is the period
during which plants establish the infrastructure on which fruits develop,
it was hypothesized that an ideal early, high-yielding plant can be
considered to be one that is late flowering, and early to physiological
maturity, even though this would obviously shorten the seed filling











process. Consequently, yield component compensation could be expected,
this expressed as a greater number of pods.


The genotypes which were closer to the model suggested seem to be Rojo
National, Rojo de Seda, and XAN 145, as shown in Tables 9 and 10 for the
two periods. From this same data it can be observed that these genotypes
do present a short seed filling period in both periods, as was expected.
However, they are not necessarily superior in Pods/Plant.


In EA these three genotypes present average to low yields (Table 9),
probably related to short seed filling periods. This situation is
maintained for EB, which had better conditions and therefore all genotypes
maximized their characteristics (Table 10).


Additional evidence is the fact that 6 3017 and Pata de Zope show
practically equal maturity values (DPM); the same is true for Rabia de Gato
and Huetar (Tables 9 and 10). In either of the two comparisons between
materials paired this way, when the number of days to flowering (FLOWER) is
greater, and pod filling period (PFP) is shorter, seed yield decreases.


The inconsistency in the compensation of components throughout the two
periods, in addition to the fact that in EB the mentioned genotypes did not
show any advantage in yield, suggests there is not enough support for the
hypothesis and the model of earliness proposed.


Rather, these results suggest a contrary hypothesis to be feasible that an
early high-yielding genotype should have an extended pod filling period,
even at the expense of days to flower. In fact, correlation of yield to
PFP was .74** and .61** in the two experiments.










CONCLUSIONS


According to results obtained in the present study, it can be concluded
that:


1. Yield and physiological maturity are highly and positively correlated
with size parameters. Environmental factors influence these
parameters.
2. Early materials tend to be more efficient than late ones as to leaf
area efficiency.
3 Three genotypes were found corresponding to the overall description of
archetype A: strong, erect stem, with limited ramification; these are
JU-84-7, G 3017, and Rabia de Gato. However, the hypothesis holds
true only partially since the expected compensation was not observed
nor was there any increase in the components Seeds/Pod and Seed
Weight. This suggests that the number of productive nodes was not
limiting for yield.
4 There was not enough evidence to support the model: late
flowering-early maturity. Although, genotypes corresponding to this
model were observed, they presented average to low yields, probably as
a consequence of their short pod filling period. In general, this
latter parameter seems critical for final yield; therefore it is not
convenient to reduce it, and it may in fact be desirable to extend it.










LITERATURE CITED

ADAMS, M.W. 1973. Plant architecture and.physiological efficiency in the
field bean. In: Potential of field bean and other legumes in Latin
America. Centro Internacional de Agricultura Tropical, CIAT, Call,
Colombia. p. 266-278.

S1981. Update: New bean archetype. Michigan Dry Bean
Dig. 5:12-13.

BRAUER H., 0. 1969. Fitogen6tica aplicada. Limusa, Mexico. 422 pp.

BUTTERY, B.R. 1970. Effects of variation in leaf area index on growth of
maize and soybeans. Crop Sci. 10:9-13.

and R.I. BUZZELL. 1972. Some differences between soybean
cultivars observed by growth analysis. Can. J. Plant Sci. 52:13-20.

CHARLES-EDWARDS, D.A. 1982. Physiological determinants of crop yield by
breeding. Hortscience 15:244-247.

DAVIS, J.H.C., and A.M. EVANS. 1977. Selection indices using plant type
characteristics in navy beans (Phaseolus vulgaris L.). -J. Agric. Sci.
89:341-348.

DONALD, C.M. 1968. The breeding of crop ideotypes. Euphytica 17:385-403,

GARCIA B., C.M. 1985. Interacci6n genotipo x ambiente en el frijol comdn
(Phaseolus vulgaris L.). Tesis de Maestria er Ciencias. Colegio de
Posgraduados. Chapingo. Mexico. 88 pp.

IZQUIERDO, J.A., and G.L. HOSFIELD. 1983. The relationship of seed
filling to yield among dry beans with differing architectural forms.
J. Amer. Hort. Sci. 108:106.

LAING, D.R. 1977. Implicaciones de la investigaci6n fisiol6gica para
mejoramiento de frijol comin (Phaseolus vulgaris L.). Centro
International de Agricultura Tropical, CIAT, Cali, Colombia. 11 pp.

P.J. KRETCHMER, S. ZULUAGA, and P.G. JONES. 1983.
Field bean. In: Smith, W.H. and S.J. Banta (eds.). Symposium on
Potential productivity of field crops under different environments.
Los Baios, Philippines, 1980 (Proceedings). Manila, International
Rice Research Institute. p. 227-248.

LEIVA R., O.R. 1977. Herencia y mejoramiento de la precocidad del frijol
(Phaseolus vulgaris L.) en el tr6pico. Tesis Mag. Sc. BogotA.
Universidad Nacional de Colombia, Instituto Colombiano Agropecuario
80 pp.










MASAYA, P. 1985. Selection for yield in early generations by total
weight. harvest index and yield/day. Report on the work done at CIAT
during 1985 as a CIAT fellow.

MENDOZA, B., E. 1973. Influencia de algunos components morfol6gicos en
el. rendimiento del frijol (Phaseolus vulQaris L.). Tesis de Maestria
en Ciencias. Colegio de Posgraduados. Chapingo, Mexico, T8 pp.

MOCK, J.J. and R.B. PEARCE. 1975. An ideotype of maize. Euphytica
24:613-623.

MOSJIDIS CH., J. 1975. Distribuci6n de la material seca entire los 6rganos
aereos de various cultivares de frijol (Phaseolus vulqaris L.).
Fitotecnia Latinoamericana 11:29-33.

POEY, D.F. 1978. Los components de rendimiento y su aplicaci6n en la
investigaci6n de cultivos. ICTA, Guatemala. Boletin Tecnico No. 3
17 pp.

STOFELLA, P.J., R.F. SANSTED, R.W. ZOBEL, and W.L. HYMES. 1979. Root
characteristics of black beans. I. Relationship of root size to
lodging and seed yield. Crop Sci. 19:823-826.

TANAKA, A., and K. FUJITA. 1970. Growth, photosynthesis and yield
components in relation to grain yield of the field bean. 3. Faculty
of Agric. Hokkaido University 59:145-238.

WALLACE, D.H., and H.M. MUNGER. 1965. Studies of the physiological basis
of yield differences. I. Growth analysis of six dry bean varieties.
.Crop Sci. 5:343-348.

1966. Studies of the physiological
basis for yield differences. II. Variations in dry matter
distribution among aerial organs for several dry bean varieties. Crop
Sci. 6:503-507.

WALLACE, D.H. 1973. Commentary upon plant architecture and physiological
efficiency in the field bean. In: Potential of field beans and other
legumes in Latin America. Centro Internacional de Agricultura
Tropical, CIAT. Cali, Colombia pp 287-294.

WILLIAMS, W.A., R.S. LOOMIS, and C.R. LEPLEY. 1965. Vegetative growth of
corn as affected by population density. II. Components of growth net
assimilation rate and leaf area index. Crop Sci. 5:215-219.

YOSHIDA, D. 1972. Physiological aspects of grain yield. Ann. Rev. Plant
Physiol. 23:437-464.





Table 1. Genetic materials used in the study,


Entry CIAT Other Seed color and
No. Identification Origin No. identification brilliance Habit Category"



1 BAT 41 Colombia Revoluci6n 79 (Nic.) Opaque red 2 !
2 JU-84-7 Guatemala G 18460 Opaque black 2 I
3 ICTA-Quetzal Guatemala DOR 41 Opaque black 2 I
4 Huetar Costa Rica RAO 29 Opaque red 2 I
5 G 3017 Guatemala Mezcla (Guatemala) Opaque mottled purple 2 L
6 A 321 Colombia Opaque cream 3 I
7 Negro Huasteco 81 M6xico DOR 60 D-145 (Guatemala) Opaque black 2 1
8 Rojo Nacional Nicaragua G 17661 Criollo (Nicaragua) Brilliant red 3 L
9 6 2858 M&xico Zacaticano (M6xico) Semi-brilliant 3 L
speckled cream
10 BAT 304 Colombia Brunca (Costa Rica) Opaque black 3 I
11 Rojo de Seda El Salvador G 4090 Criollo (El Salvador) Semi-brilliant red 3 L
12 Desarrural Honduras G 4477 C-0-1-63A (Honduras) Brilliant red 3 L
13 XAN 112 Colombia Opaque black 2 I
14 Rabia de Gato Guatemala G 2997 Opaque-black 2 L
15 Pata de Zope Guatemala G 17648 Opaque black 3 L
16 XAN 145 Colombia Opaque black 2 I


I = improved; L = Land race


CIAT-Palmira, 1985.











Table 2. Meanings of acronyms used in Tables 3-13.


Meaning


FLOWER

DPM

MAXTDW

LAD

MAXLEN

MAXHEI

MAXLAI

CGR30

NAR30

RGR30

PFP

P/P

S/P

SW

HI

YIELD

YIELD/DAY

SDWS

SDWB


Acronyms


Days to flowering

Days to physiological maturity

Maximum total dry weight

Leaf area duration

Maximum length of stem

Maximum height

Maximum leaf area index

Crop growth rate 30 days after emergence

Net assimilation rate 30 days after emergence

Relative growth rate 30 days after emergence

Pod filling period

Pods per plant

Seeds per pod

Seed weight

Harvest index

Yield

Yield per day

Seed dry weight in the stem

Seed dry weight in the branches


__ ________1_1_______1___





Table 3. Parameters of size and efficiency of early and late genotypes. Average data of three replications.
Experiment A. CIAT-Palmira, 1985.



MAXTDW LAD NODES/m= MAXLEN MAXHEI MAXLAI CGR30 NAR30 RGR30
(g/m2) AT MAT. (cm) (cm) (m2/m2) (g!m2/d) (g/m2/d) (gig/d)



8 3017 136.4 34.2 310.8 51.4 43.7 1.413 4.85 3.95 0.0530
Pata de Zope 132.0 31.1 234.0 53.2 48.9 1.417 4.95 4.61 0.0641
Rabia de Sato. 232.4 47.4 262.5 67.6 50.2 1.907 7.49 4.99 0.0687
Huetar 157.2 42.3 292.4 41.5 37.4 1.663 4.61 3.65 0.0549
G 2858 253.2 53.7 612.2 94.0 34.9 1.511 6.63 4.36 0.0533
XAN 145 192.6 49.9 365.0 69.2 54.9 1.768 6.87 4.58 0.0667
Desarrural 214.1 64.6 548.6 96.0 42.3 2.101 5.62 3.13 0.0487
Rojo de Seda 263.9 74.0 369.5 95.4 48.3 2.445 8.56 4.46 0.0734
XAN 112 182.4 46.8 384.4 71.8 52.2 1.589 6.05 5.11 0.0698
Rojo Nacional 160.3 47.3 498.6 90.0 38.9 1.690 4.56 3.34 0.0541
BAT 41 193.8 53.4 420.6 64.0 45.7 1.732 5.60 3.65 0.0575
JU-84-7 322.3 70.1 387.4 114.1 52.9 2.114 7.96 5.20 0.0823

BAT 304 320.9 77.3 328.5 118.5 55.1 2.312 9.99 5.53 0.0808
Negro Huasteco 81 256.9 63.0 387.8 64.0 53.7 1.989 6.92 5.06 0.0779
ICTA-Quetzal 286.4 76.2 509.4 84.2 63.7 2.447 8.58 5.21 0.0858
A 321 397.4 108.3 547.1 184.6 49.8 3.164 9.14 4.01 0.0706


.x 231.4 58.7 403.7 84.8 48.3 1.954 6.77 4.43 0.0663
S.D. 74.9 19.5 110.9 34.3 7.51 0.467 1.72 0.74 0.01!8


Meanings of acronyms are in Table 2.





Table 4. Parameters of size and efficiency of early and late genotypes. Average data of three replications.
Experiment B. CIAT-Palmira, 1985.



MAXTDW LAD NODES/m2 MAXLEN MAXHEI MAXLAI CGR30 NAR30 RGR30
(g/m2) AT MAT. (cm) (cm) (o2/m2) (g/m2/d) (g/m2i d) (g/g/d)



8 3017 500.0 91.9 455.0 106.0 46.2 3.584 13.1 4.26 0.0618
Pata de Zope 431.0 99.3 303.0 105.2 59.2 3.785 14.5 4.26 0.0655
Rabia de Sato 483.0 101.9 419.0 94.7 55.9 3.773 16.0 4.91 0.0732
Huetar 383.0 98.5 425.9 66.5 57.2 3.797 13.8 4.13 0.0686
G 2858 493.0 101.0 708.9 114.3 38.6 3.215 14.4 4.80 0.0625
XAN 145 479.0 111.7 487.7 104.9 62.3 3.983 13.7 4.20 0.0677
Desarrural 481.0 141.8 538.8 117.4 45.9 4.599 13.7 3.64 0.0640
Rojo de Seda 491.0 161.6 459.5 135.9 53.6 5.281 15.2 3.57 0.0665
XAN 112 428.0 112.8 399.3 120.5 64.5 3.993 10.3 3.40 0.0520
Rojo Nacional 411.0 123.3 649.4 110.1 46.0 4.535 11.7 3.45 0.0649
BAT 41 474.0 126.9 499.3 103.8 61.2 4.779 13.6 3.70 0.0614
JU-84-7 545.0 143.7 408.7 152.8 60.1 4.941 16.4 4.79 0.0806

BAT 304 648.0 144.9 443.0 160.6 59.7 4.89.8 15.1 4.03 0.0665
Negro Huasteco 81 586.0 182.9 443.0 120.2 81.9 5.823 13.1 3.51 0.0669
ICTA-Quetzal 616.0 173.1 523.6 125.2 81.3 5.664 12.8 3.48 0.0687
A 321 653.0 196.8 596.5 191.4 61.2 5.475 12.8 3.02 0.0559


x 506.4 132.0 485.0 120.6 58.4 4.508 13.8 3.95 0.0654
S.D. 82.0 32.9 101.1 29.0 11.6 0.802 1.54 0.56 0.0065


Meanings of acronyms are in Table 2.





Table 5. Correlation coefficients among some characteristics of plant efficiency, maturity (DPM), and
-yield (YIELD), during two periods for n = 16 (upper part) and n = 12 (lower part). CIAT-Palmira, 1985.



Experiment A Experiment B
Characteristic DPM YIELD DPM YIELD
(days) (kg/ha) (days) (kg/ha)



Maximum total dry weight (g/m2) 0.79*** 0.87*** 0.66** 0.87***
0.60* 0.81** 0.11 0.81**
Leaf area duration 0.86*** 0.83*** 0.87*** 0.72**
0.76** 0.62* 0.69* 0.41
Total nodes at maturity (n/m2) 0.55* 0.21 0.43 0.21
0.59* 0.07 0.47 0.05
Maximum length of stem (cm) 0.68** 0.83*** 0.68** 0.81***
0.74** 0.59* 0.50 0.65*
Maximum height (cm) 0.52* 0.35 0.47 0.29
0.15 0.40 0.05 -0.12
Maximum leaf area index (m2/m2) 0.79*** 0.78*** 0.79*** 0.64**
0.54 0.51 0.59* 0.42


*, **, *** Significant at 0.05, 0.01 y 0.001, respectively.






Table 6. Correlation coefficients among some characteristics of plant efficiency, maturity (DPM), and
.yield (YIELD), during two periods for n = 16 (upper part) and n = 12 (lower part). CIAT-Palmira, 1985.



Experiment A Experiment B
Characteristic DPM YIELD DPM YIELD
(days) (kg/ha) (days) (kg/ha)



Yield/day (kg/ha/day) 0.58* -0.03
0.28 -0.48
Harvest index (7.) 0.25 0.64t* -0.29 0.19
0.05 0.40 -0.28 0.39
Crop growth rate (g/m2/day) 0.67** 0.75*** -0.34 0.21
0.42 0.68* -0.31 0.57
Net assimilation rate (g/m2/day) 0.28 0.30 -0.71** -0.19
0.04 0.44 -0.56 0.40
Relative growth rate (g/g/day) 0.61* 0.50* -0.27 0.18
0.31 0.60* -0.23 0.65*


*, **, *** Significant at 0.05, 0.01 y 0.001, respectively.
Rates at 30 i~ys after emergence.






Table 7. Analysis of variance for growth parameters during two periods. CIAT-Palmira, 1985.



Experiment A Experiment B
Mean square C.V. (.) Mean square C.V. (7.)



Days to flowering 23.5388** 2.3 15.4819** 1.8
Days to physiological maturity 55.6569** 1.2 65.1555** 0.7
Maximum total dry weight 12340** 17.3 15745 17.5
Leaf area duration -854.87** 14.3 2339.0** 8.7
Total nodes at maturity 30213** 14.2 21658** 11.0
Maximum length of stem 2704.36** 10.2 1899.39?** 8.2
Maximum height 137.90** 6.9 314.38** 6.2
Maximum leaf area index 0.4871** 16.4 1.3843** 3.9
Crop growth rate 6.379 21.6 5.586 15.9
Relative growth rate 0.00031* 17.1 0.000099 12.7
Net assimilation rate 1.218 20.4 0.784* 15.1
Harvest index 52.29** 6.0 50.29* 7.3
Yield 53795** 17.8 316306* 14.0
Yield per day 89.966** 17.7 54.51 14.0


*, ** Significant at 0.05 and 0.01, respectively.
Rates at 30 days after emergence.





Table 8. Parameters of development and yield of early and late genotypes during two
three repetitions. CIAT-Palmira, 1985.


periods. Average data of


_Experiment A -Experiment 8__
FLOWER DPM HI YIELD YIELD/DAY FLOWER DPM HI YIELD YIELD/DAY
(days) (days) (7.) (kg/ha) (kg/ha/d) (days) (days) (7) (kg/ha) (kg/ha!d)



G 3017 29.2 57.3a 57.5 872 15.5 28.5 55.9a 66.4 2616b 47.2
Pata de Zope 30.5 57.5a 52.9 510 9.1 29.1 56.Oa 54.5 2364 42.1
Rabia de Gato 31.4 60.3b 55.8 990 16.2 30.7 58.0b 59.7 2509b 43.1
Huetar 33.8 60.4b 40.8 723 11.8 32.2 57.9b 62.3 2034 35.3
6 2858 31.8 62.9c 55.0 864 13.7 29.6 63.0c 56.2 2410b 38.2
XAN 145 37.7 63.2 55.9 983 15.6 33.9 64.9 56.7 2427b 37.5
Desarrural 33.5 63.9 52.7 848 13.2 31.7 65.1 64.8 2534b 38.9
Rojo de Seda 38.0 64.3 54.4 901 14.1 34.3 65.8 55.3 2449b 37.3
XAN 112 36.1 65.2 50.8 750 11.6 33.7 66.0 49.9 2064 31.3
Rojo Nacional 37.2 64.9 55.4 679' 10.5 34.7 65.8 63.8 2490b 37.8
BAT 41 35.6 64.5 49.3 823 12.8 33.3 65.2 57.5 2524b 38.7
JU-84-7 36.3 66.2 56.8 1555c 23.3 32.9 63.1 60.9 3128ab 49.3

BAT 304 35.9 68.1 61.0 1887b 27.7 32.3 67.5 61.4 2916ab 43.1
Negro Huasteco 81 39.2 70.0 54.1 1315c 18.9 37.2 69.7 51.9 2687b 38.7
ICTA-Quetzal 39.5 72.7 49.5 941 12.8 37.0 70.6 53.6 3048ab 43.3
A 321 38.2 73.9 61.6 2445a 33.1 35.5 74.0 60.8 3467a 46.9


x 35.2 64.7 53.9 1068 16.2 32.9 64.3 58.5 2604 40.6
S.D. 3.15 4.77 4.93 503 6.55 2.59 5.19 4.77 376 4.79


Values followed by the same letter are
Meanings of acronyms appear in Table 2.


statistically equal at 0.05.





Table 9. Parameters of development and yield and its components of early and late
repetitions. Experiment A. CIAT-Palmira, 1985.


genotypes. Average of three


Genotype FLOWER DPM PFF P/P S/P SW HI YIELD YIELD!DAY
(day(day) days) (days) (nm ) (.) (kg!ha) (ko!ha!d)



6 3017 29.2 57.3a 28.2 10.3 3.88 163.3 57.5 872 15.5
Pata de Zope 30.5 57.5a 26.9 8.3 3.72 157.8 52.9 510 9.1
Rabia de Gato 31.4 60.3b 28.9 11.1 4.20 177.2 55.8 990 16.2
Huetar 33.8 60.4b 26.6 9.0 4.18 151.6 40.8 723 11.8
6 2858 31.8 62.9c 31.1 8.8 2.92 300.0 55.0 864 13.7
XAN 145 37.7 63.2 26.5 10.1 3.73 147.5 55.9 983 15.6
Desarrural 33.5 63.9 30.4 7.6 3.62 215.4 52.7 848 13.2
Rojo de Seda 38.0 64.3 26.3 10.9 3.57 233.2 54,4 901 14.1
XAN 112 36.1 65.2 29.1 10.4 3.59 174.9 50.8 750 11.6
Rojo Nacional 37.2 64.9 27.7 9.6 3.48 159.9 55.4 679 10.5
BAT 41 35.6 64.5 28.8 8.1 3.70 138.2 49.3 823 12.8
JU-84-7 36.3 66.2 29.9 15.0 4.80 172.6 56.8 1555c 23.3

BAT 304 35.9 68.1 32.2 15.1 5.07 177.8 61.0 1887b 27.7
Negro Huasteco 81 39.2 70.0 30.9 11.7 4.91 177.9 54.1 1315c 18.9
ICTA-Duetzal 39.5 72.7 33.1 11.4 4.51 142.0 49.5 941 12.8
A 321 38.2 73.9 35.7 11.8 4.37 329.3 61.6 2445a 33.1


x 35.2 64.7 29.5 10.6 4.02 188.7 53.9 1068 16.2
S.D. 3.15 4.77 2.64 2.17 0.59 55.3 4.93 503 6.55


Values followed by the same letter are
Meanings of acronyms are in Table 2


statistically equal at 0.05.





Parameters development and yield and its components of early and late genotypes.


repetitions. Experiment B.


CIAT-Palmira,


Genotype FLOWER DPM PFF P/P S/P SW HI YIELD YIELD/DAY
(days) (days) (days) (mg) (:) (kg/ha) (kg/ha/d)



8 3017 28.5 55.9a 27.4 17.6 4.69 218.5 66.4 2616b 47.2
Pata de Zope 29.1 56.0a 26.9 13.8 4.64 221.5 54.5 2364 42.1
Rabia de Gato 30.7 58.0b 27.2 16.1 4.25 226.3 59.7 2509b 43.1
Huetar 32.3 57.9b 25.7 15.4 4.74 190.1 62.3 2034 35.3
G 2858 29.6 63.Oc 33.4 13.9 3.10 385.4 56.2 2410b 38.2
XAN 145 33.9 64.9 30.9 18.3 4.57 193.7 56.7 2427b 37.5
Desarrural 31.7 65.1 33.3 15.2 4.13 284.3 64.8 2534b 38.9
Rojo de Seda 34.3 65.8 31.5 10.1 4.77 313.3 55.3 2449b 37.3
XAN 112 33.7 66.0 32.3 16.2 3.87 223.5 49.9 2064 31.3
Rojo Nacional 34.7 65.8 31.1 15.0 4.51 227.1 63.8 2490b 37.8
BAT 41 33.3 65.2 31.9 17.9 4.94 194.7 57.5 2524b 38.7
JU-84-7 32.9 63.1 30.2 17.9 5.39 223.9 60.9 3128ab 49.3

BAT 304 32.3 67.5 35.2 19.3 5.49 237.1. 61.4 2916ab 43.1
Negro Huasteco 81 37.2 69.7 34.5 12.0 6.21 229.5 51.9 2687b 38.7
ICTA-Quetzal 37.0 70.6 33.6 16.5 5.52. 211.9 53.6 3048ab 43.3
A 321 35.5 74.0 38.5 17.9 4.86 357.5 60.8 3467a 46.9


x 32.9 64.3 31.4 15.8 4.75 246.1 58.5 2604 40.6
S.D. 2.59 5.19 3.33 2.48 0.72 58.3 4.77 376 4.79


Values followed by the same
Meanings of acronyms are in


letter are
Table 2.


statistically equal at 0.05.


1985.


Table 10.


Average of three







Table 11. Maximum height (MAXHEI), maximum length of stem (MAXLEN), seed dry wright in the stem (SDWS), and in
the branches (SDWB) during two periods. Average of three replications. CIAT-Palmira, 1985.



Experiment A Exoeriment B
MAXHEI MAXLEN SDWS SDWB MAXHEI MAXLEN SDWS SDWB
(cm) (cm) (g/m2) (g/mb ) (cm) (cm) (g/m2) (g/2)



6 3017 43.7 51.4 46.2 106.01 168.0 85.5
Pata de Zope 48.9 53.2 59.2 105.2 183.0 9.7
Rabia de Gato 50.2 67.6 55.9 94.7 110.3 55.2
Huetar 37.4 41.5 57.2 66.5 52.8 35.7
G 2858 34.9 94.0 38.6 114.3 73.3 152.0
XAN 145 54.9 69.2 62.3 104.9 87.5 170.5
Desarrural 4 42.3 96.0 45.9 117.4 90.2 162.7
Rojo de Seda 48.3 95.4 -- 53.6 135.9 73.2 177.3
XAN 112 52.2 71.8 64.5 120.5 93.5 116.2
Rojo Nacional 38.9 90.0 46.0 110.1 53.2 166.7
BAT 41 45.7 64.0 61.2 103.8 94.0 178.5
JU-84-7 52.9 114.1 60.1 152.8 187.3 69.2

BAT 304 55.1 118.5 59.7 160.6 140.0 135.7
Negro Huasteco 81 53.7 64.0 81.9 120.2 159.2 89.3
ICTA-Quetzal 63.7 84.2 81.3 125.2 123.2 119.3
A 321 49.8 184.6 61.2 191.4 118.7 216.8


x 48.3 84.8 -58.4 120.6 113.2 121.3
S.D. 7.51 34.3 11.6 29.0 43.6 58.9






Table 12. Analysis of variance for development, yield, and growth data during two periods. CIAT-Palmira, 1985.



Experiment A Experiment B
Mean square C.V. (.) Mean square C.V. (7.)


Days to flowering

Days to physiological maturity
Pod filling period
Pods/plant
Seeds/pod
Seed weight
Harvest index
Yield
Yield per day

Maximum height
Maximum length of stem
Seed dry weight in the stem
Seed dry weight in the branches


23. 5388**

55.6569**
17.4569**
10.861*
0.7469*
7469.27**
52.29**
537957**,
89.966**
137.90***
2704.36**


23
1.2
3.3
20.8

13.7
4.6

6.0
17.8
17.7
6.9
10.2


15.4819**

65.1555**

27.0069**
13.9611**
1.1571**
7918.6**

50.29*
316306*
54.51
314.38**
1899.39**

4283.3.3*
7427.2**


1.8
0.7
2.4
11.7
9,4
5.0

7.3
14.0
14.0
6.2
8.2
54.6
47.9


*, **, *** Significant at 0.05, 0.01 and 0.001, respectively.


~---







Table 13. Correlation coefficients among yield (YIELD), its components, and harvest index (HI) during two periods
for n = 16 (upper part) and'n = 12 (lower part). CIAT-Palmira, 1985.



Experiment A Experiment B
S/P SW HI YIELD S/P SW HI YIELD



Pods/plant (P!P) 0.78*** 0.02 0.53* 0.70** 0.09 -0.32 0.38 0.38

0.67* -0.07 0.41 0.83*** 0.27 -0.63* 0.26 0.29

Seeds/pod (S/P) -0.22 0.20 0.63** -0.44 -0.07 0.51*

0.55 -0.06 0.62* -0.67* 0.29 0.47

Seed weight (SW) 0.44 0.51* 0.01 0.28

0.24 0.07 -0.14 0.05

Harvest index (HI) 0.64** 0.19

0.40 0.39


*, **, *** Significant at 0.05, 0.01 and 0.001, respectively.
Meanings of acronyms are in Table 2.









+ = LATE MATURING GENOTYPES


2
*


5 .4 L6


4 8


+7


+3


C
S30

*;- C- -. '*

0





..10
_-. ---,


55
55


.5 0 0.

55 60 65 70


75 ________


DAYS TO PHYSIOLOGICAL MATURITY

Fig. 1. Relationship between seed yield/day and number of days to maturity during two planting
seasons. Means from three replications. CIAT-Palmira. 1985.


--40


Sr = 0.58*
r2 = 0.28
' L


12 1
16 1
16 II


. 3


rl = -0.03
r = -nfl.


_-_-"-


_-I-


0








4+ LATE MATURING GENOTYPES


1800





1400



',4
E


o
-i



6 100





200
200


+10


3
I +


300 g/m'


200 g/m'


ri = -0.53*
r = -0.7g90


0.16 0.20 0.24 0.28 0.32 0.19 0.22 0.26 0.30 0.34


SEED WEIGHT

2
Fig. 2. Relationship among number of seeds/m2 and seed weight during two plantings. Continuous lines
rAnrnsnnt. constant vield. means of three reDlications. CIAT, Palmira, 1985.


170 g/m' 6
i +


0.12










STRATEGIES AT CIAT FOR INCREASING YIELD POTENTIAL OF COMMON BEANS
--- FINISHING THE DOMESTICATION PROCESS


Jeffrey W. White**


Since the founding of the Bean Program at CIAT, there has existed interest
in finding ways to increase the-yield potential of beans (Adams, 1973;
Wallace, 1973). This interest has continued to the present day, and if
anything, has increased with successes in controlling other production
problems.


The present strategy of the Program contains two basic components. One
consists of continuing breeding efforts based on selection for yield,
considering that, to date, it has not been possible to identify reliable
morphological or physiological parameters for use as selection criteria for
yield. The other component is simply to continue the search for such
characteristics. It is this second component which provides the subtitle
for this presentation since the present philosophy of research on selection
criteria is that beans are still a very rustic crop, adapted to cropping
systems with low plant densities, infertile soils, strong weed competition,
and other all too familiar problems. In order to increase yields,
cultivars are needed which are adapted to agronomic management which
reduces such stresses.


In this presentation, basic aspects of the two strategies will be discussed
after a brief review of some strategies notable for their failure. It
should be appreciated that the intent is to describe the efforts of CIAT in





SReport presented at the XXXIII Meeting of the PCCMCA, Ciudad de
Guatemala. 30 April 1987.


Physiologist, CIAT, A.A. 6713, Cali, Colombia.





2




the context of the agro-ecological conditions of its experiment stations,
and not to present a universal formula for solving the yield potential
problem.


Historical Review


Suggestions on ways to increase yield potential of beans have been
numerous. Although CIAT is far from having investigated all the
possibilities, it has tried a great many.


Yield Components:


Applying yield components in their simplest form, it is conceivable that
simply by intermating materials with different levels of yield components
and selecting recombinants with high values of certain components, new,
higher yielding materials may be developed. This strategy assumes that
each component is under independent genetic control. Unfortunately, as
noted by Adams (1967), yield components generally show strong interactions
such that an increase in one component tends to be associated with a
decrease in others. Adams called this phenomenon "yield component
compensation", and noted that its occurrence suggested that there is
competition for limited resources within a bean plant. Such compensation
has been detected in many studies at CIAT, both with bred lines (e.g. White
1981; Fig. 1) and in segregating populations (Nienhuis and Singh, 1985;
Table 1).


Given this reality, work at CIAT has steered away from this approach,
although admittedly it remains to be determined whether an optimum
combination of yield components can be defined for beans.










Biomass or Size:


In agreement with work on yield components, a consistent tendency for
larger plants to yield more has been noted, independent of whether size is
measured as biomass (dry weight), leaf area duration, or some other size
parameter (Table 2). It could be said that under conditions at CIAT, bean
yields are limited by supply, that is source strength, rather than demand,
or sink strength. This has suggested two "sub-strategies": search for
cultivars which grow more rapidly or for cultivars which, because they grow
for a longer period, have more growth.


For the first alternative, various approaches have been considered. The
simplest is simply to increase the rate of photosynthesis. However,
studies by Kueneman and co-workers (1979) indicated that selection for
increased leaf photosynthetic rates would be ineffective in beans. Similar
results in other crops (Gifford and Evans, 1980) have served to dissuade
CIAT from following this approach further. 'Nonetheless, it is clear that
photosynthesis in beans requires further study. Comparing leaf
photosynthetic rates reported over 20 years, one notes a tendency for rates
to increase with time (Table 3). Presumably these do not reflect genetic
changes, it being more likely that measurement techniques have improved.
It is also interesting to note that in work with Viona munoo, a
significant correlation was found between yield and photosynthetic rate
during podfill (r = 0.66, significant at the P=0.01 level, but not during
other growth phases (Chandra et al., 1985).


Another possibility for increasing growth rate would be to achieve more
efficient light interception. Among various alternatives, greater lodging
resistance seems the most crucial under conditions at CIAT. In a study on
effects of delayed maturity on yield (Masaya, personal communication),
there was no clear treatment effect with lodging, but with a trellis which
prevented lodging, a mean yield increase of 16% was obtained (Table 4). As
a further observation, it merits note that in almost all studies at CIAT on










yield potential, lodging appears to occur sufficiently early to affect crop
growth and yield.


Finally, one might attempt to increase biomass accumulation through
extension of the crop growth cycle. Work using long days to induce delayed
maturity has demonstrated the potential for increasing yields through late
maturity (Laing et al., 1984; Masaya, personal communication).
Nonetheless, notwithstanding 7 or 8 years of efforts to select late
maturing materials at CIAT, no materials combining late maturity with
higher yields have been obtained. The main problem appears to be that
selection for lateness results in unintentional selection for materials
highly sensitive to photoperiod, and in reality, such materials are late
because of their poor adaptation. This suggests that future selection for
late maturity should restrict selection to materials previously shown to
have good adaptation, and at the same time, use selection criteria which
minimize the chances of selecting materials with poor adaptation.


Harvest Index:


Besides trying to increase total biomass, one might increase the efficiency
of distribution of dry weight, the most obvious approach being to increase
harvest index. However, various lines of evidence suggest that this
strategy holds little promise for conditions at CIAT.


The first difficulty is that in contrast to crops such as wheat and rice,
where harvest indices of traditional and improved cultivars vary between 30
and 55% (Kertesz, 1984), the normal range of variation at CIAT is generally
on the order of 50 to 60%. This suggests that harvest index in beans is
already very high. Indeed, one might ask whether harvest indices are too
high if this increases tendency for lodging.


Lack of variability -on harvest index is also reflected directly in the
rarity of trials which show a significant correlation between yield and










harvest index (Table 2). This scarcity is actually worse than it seems
when one considers that the statistical artifact introduced by correlating
the two parameters should make the correlations artificially greater. The
value for biomass includes yield (biomass = vegetative weight + seed
yield), so one usually expects a large correlation although it is
impossible to determine its significance level. This effect is so strong,
that it has been shown that if pairs. of random numbers are used to
calculate hypothetical values of harvest index, a high correlation may be
obtained (Charles-Edwards, 1982). This point is seldom discussed by
advocates of harvest index, so we offer Figure 2 as an example of a "highly
significant" correlation generated with 20 pares of random numbers.


Perhaps the argument of greatest weight against use of harvest index is
that in comparing its effectiveness as a selection parameter, it has proven
inefficient compared to simpler alternatives (Table 6). Plant breeders
working with other crops appear to have had similar experiences. For
example, Kramer (1984), working with wheat, concluded that harvest index
served as a selection criterion only when one did not expect variation in
total biomass, and that in that case, selection directly for individual
plant yield is equally effective, while requiring less labor.


Other strategies:


Other possibilities for increasing yield have also been considered: search
for an optimal combination of morphological characteristics (White, 1981),
increase the efficiency of pollination, increase nutrient availability
(especially nitrogen) through foliar fertilization, among others. Although
some of these approaches have not been discarded, they have not changed the
basic conclusion that, under conditions at CIAT, bean crops always seem to
show strong limitations of assimilate availability ("source"), while demand
("sink strength") is usually adequate.









Breeding for Increased Yield


Confronted with the absence of reliable selection criteria, efforts on
yield breeding at CIAT have evolved a strategy of selection directly for
yield. To optimize the selection process, studies on ways to identify
promising parents and optimal agronomic practices for selection have been
conducted.


To date, the principle approach for identification of good parents has been
use of combining ability studies. In a study of 80 lines grown at Palmira
and Quilichao, a great range of variability in general and specific
combining ability was detected. While materials such as A 375 and BAT 477
showed high, positive general combing abilities (GCA's), some well known
cultivars such as Jamapa and Porrillo Sintetico had negative GCA's
suggesting little promise as parents (Table 7).


Studies on nursery management are still in preliminary stages, but it is
hoped to define optimal conditions for yield selection. One of the first-
aspects being investigated is efficiency of individual plant selection
under different plant populations.


Given the variability in GCA, a strategy which emphasizes selection among
populations is being pursued, with a deemphasis in individual plant
selection in early generations. It is hope that evaluating yields of
populations from F2 onwards will not only result in production of
populations with high frequencies of desirable genotypes, but
identification of parents with greatest GCA. In practical terms, yield
tests are being performed from the F2 to the F4, using a bulk-pedigree
method (Fig. 3). For each group of crosses (e.g. for a combination of
grain types and diseases resistances), populations are planted in lattice
designs with two replicates. Agronomic management is identical to that
used in yield trials of advanced lines, including populations of 200,000
plants/ha and bordered yield plots. To assure sufficient seed for










subsequent generations, bulks are formed by harvesting one pod per plant.
In the F5, a spaced planting is used to permit individual plant selection.
Seed of the F6 is again used in replicated yield trials, and in F7 final
yield tests in three locations (Palmira, Quilichao and Popayan) are
performed before distribution to national programs and CIrT uniform
nurseries.


To accelerate the accumulation of desirable genes, a recurrent selection
strategy is also being followed. It is similar to the preceding system,
but differs in specific details (Fig. 4). Among these are yield tests in
the FI, intercrossing among the most promising populations, individual
plant selection in F3, and return to intermating in the F6 generation.
Both breeding strategies require large quantities of Fl seed and imply
large numbers of yield plots. This implies a large expenditure of
resources of the Bean Program, but it was felt better to continue with a
difficult and costly approach which shows promise, rather than continue
with strategies which did not seem to produce the desired results.


In summary, it can be said that the main yield breeding strategy is based
on development of populations with high mean yields, the work being guided
by studies of combining ability. However, it is worth noting that this
approach has been criticized for ignoring the potential importance of
variablity within populations, and favoring parents with good competitive
ability (probably type III's). The need for continuing studies on
selection strategies is apparent.


The Physiology Strategy


Although it is hoped that yields can be increased through direct selection
for yield, a need is still seen for identifying more efficient selection
criteria. Identifying better criteria should facilitate the ongoing
selection process or help identify particularly promising parents. And
there is also no guarantee that seeking progressive increases in yield will











be as productive as redesigning the crop, such as has been done in other
crops such as rice (Chandler, 1968), wheat (Evans et al., 1975) and soybean
(Cooper, 1985).


In work at CIAT an attempt has been made to investigate various possible
strategies for increasing yield potential, but at the present, the main
effort is centered upon the hypothesis that traditional bean cultivars are
adapted to cropping systems which imply sacrificing yield potential in
exchange for reduced risk, production costs or other problems. We can say
that traditional systems represent a state of semi-domestication where bean
plants are obliged to expend a high portion of resources simply in
surviving among problems of weed competition, low soil fertility, drought
stress, and attacks of insects and diseases. If we wish to increase yield
potential dramatically, we should not only search for new plant types, but

Provide then with adequate agronomic conditions where stresses are
minimized. This reality has lead physiological studies to pursue two
parallel lines of investigation, one of modification of agronomic practices
and the other of searching for genotypes which are adapted to such
practices.


The Agronomic Component


In order to define agronomic practices for a type of bean cultivar which
still may not exist, attention has been given to practices such as
increased density, reduced spacing between rows, and increased fertilizer
application, which have accompanied yield increases in the crops. In
commercial soybean crops planted at a row spacing of 0.17 m, populations of
700.000 plants.ha-' are now in use (Cooper, 1985). Data for cereal crops
are difficult to extend to beans, but the importance given to reduced row
spacings and increased populations is clear (Chandler, 1968; Duncan,
1968). Such changes represent a drastic shift from traditional practices
at CIAT with 0.6 m row spacings and maximum populations of 250.000
plants.ha-1. However, given that the practices being sought are for











genotypes which still may not exist in common bean, little importance is
being given to previous recommendations for practices with beans.


The first trials performed within the framework of this strategy compared
response of traditional and erect genotypes to row spacing and po-pulation.
In a trail with four row spacings, but conserving a constant popLlation of
200.000 plants.ha-1, crop dry weight at 56 days increased 20% in erect
genotypes and 14. in traditional materials, comparing the 0.6 m spacing
(traditional in CIAT) and 0.2 m spacing (Table 8). However, at harvest,
the 0.2m spacing gave the lowest yields, the 0.45 m spacing offering an 11%
increase in traditional lines, and only 3% increase with erect lines. This
suggested that the treatments were effective in producing an increase in
biomass, but that other factors during podfill or maturation reduced the
efficiency of conversion of dry matter to yield. The most probable
candidate was lodging, and this is being subjected to further study.


In any case, the data demonstrate the ability of traditional materials to
adapt to a wide range of agronomic practices. Fig. 5 also illustrates this
phenomenon for four early maturing lines where canopy cover at 18 days was
much greater with a 0.2 m spacing, but as the cultivars grew, differences
among row spacing treatments disappeared. For the moment, a row spacing of
0.3 m has been adopted as a provisional standard for intensive agronomy.


Assuming that this spacing is preferable to a 0.6 m spacing, it was
expected that plant populations could be increased since the 0.3 m spacing
permits a better spacial distribution of plants. In the first two trials
evaluating effects of increased population at different row spacings a
significant spacing by density interaction was detected in the first trial,
but not in the second, although yields were always higher at 0.3 m row
spacing (Table 9).


For the moment, 300.000 plants.ha-1 is being used with the 0.3 m spacing,
but it is recognized that this value is artificial in the absence of the











genotypes we are searching for.


As a third component of agronomic management, yield increases have been
sought through split nitrogen applications. Given that the majority of
studies at CIAT-Falmira have indicated that nitrogen is not limiting, and
that one of the supposed attractions of bean crops is their ability to fix
nitrogen, this sub-strategy requires further justification.


First, it was noted that in a 1 ton.ha-' yield increase represents an
increase of 220 to 230 kg of protein, which in turn implies making an
additional 15 to 16 kg.ha-1 of nitrogen available to the crop. Assuming
losses due to volatilization, leaching and nitrogen in crop residue, the
total additional N required could easily be 30 kg.ha-1




Studies in soybean and common bean suggest that the same high nitrogen
requirement is a key factor in determining the drop in efficiency of
photosynthesis during podfill (Sinclair and de Wit, 197 ; Tanaka and
Fujita, 197 ). Just when the crop would benefit most from a high
photosynthetic rate, nitrogen is remobilized out of leaves to supply
growing pods. This results in a very close relation between leaf
senescence and pod set. Comparing weights of leaves and pods at maturity
(relative to total plant weight) under various levels of pod removal, a
linear relation between leaf and pod weight was found (Fig. 6).


Although it would be preferable for a bean crop to provide its own nitrogen
through fixation, we have assumed for the moment that additional N will
have to be supplied through fertilizer, but with special emphasis on making
it available in a manner which will assure efficient use. Foliar
applications were discarded given doubts concerning their adverse affects
(Gray and Akin, 1984), and for the moment, emphasis is being given to
weekly applications of urea applied in solution to the soil. Comparing
treatments of 10 and 20 kg of N per week starting at onset of flowering, N










applications were associated with a 10% yield increase with 0.6m row
spacing, but gave a 10% yield reduction for the 0.3 m spacing (Fig. 7). A
possible explanation is that the N treatment or 0.3 m spacing function
separately to increase leaf growth, and thus yield, but when combined,
their effect is to produce a supra-optimal level of leaf development, or a
very vegetative plant with little lodging tolerance.


In all of the agronomic study, it has been difficult to interpret results
due to doubts about using in plant types which do not conform to our ideal.
To remedy this situation in future studies, an attempt will be made to
reduce lodging through artificial supports. In addition, growth regulators
such as CCC or B-9 will be used to produce plants of short stature and less
tendency to lodge.


The varietal Component:


The preceding discussions underline the urgent need.to find materials with
improved response to narrow row spacing and higher populations. Taking as
a reference point the 0.3 m row spacing with 30 plants m-2, materials from
.the VEF and breeders' nurseries are now being screened for such a response.
Since such nurseries are managed with traditional spacings, selection
criteria are limited to erect habit (type 2a), pod load and general
adaptation. No use is made of yield data because of the fear that this
will again lead to selection of traditional plant types adapted to wide
spacings and low densities. From the nurseries, materials are passed to
yield trials (lattices with 3 replicates) managed with narrow rows.


When agronomicc practices have been further refined, and a first group of
materials is identified for outstanding performance under these conditions,
breeding for this system will be started. The basic strategy could simply
be to follow the schemes outlined in Fig. 3 and 4, but employing the
intensive management practices. It would also be useful to select for
specific characters such as lodging resistance and nitrogen response. To











date, materials of growth habit type I have been ignored in our studies,
but given the success with determinate soybeans (Cooper, 1985), these also
might merit consideration.


A special problem for breeding efforts is possible adverse affects of plant
competition during the selection process. If one accepts that a desirable
characteristic for traditional cropping systems is outstanding competitive
ability, while one of the advantages of the proposed new materials would be
reduced competitiveness, it is easily imagined that a selection process
based on individual plant vigor or repeated use of bulks could prove
counterproductive. This problem has been well documented in rice (Jennings
and de Jesus, 1968), and Jennings (1968) suggested that it may be avoided
by thinning out the most vigorous plants with large leaves at the onset of
flowering. In CIAT, some researchers have argued that levels of
competition are not so extreme in beans, so the problem would be much less
severe. However, plant death at high densities is easily demonstrable, and
presumably reflects effects of excessive competition (Fig. 8).


Conclusion


While we are confident that ways can be found to increase bean yield
potentials, and that searching for erect architecture combined with
appropriate agronomic practices is a promising way to achieve this increase,
there is little doubt that the increases will not come easily. Since the
introduction of the wheat cv. Norin 10 as a source of genes for dwarf
architecture in 1946, 15 years passed before the release of the first
commercial dwarf wheat in the U.S.A. (Gale and Youssefian, 1985). In the
work of Cooper (1985) on dwarf, semi-determinate soybeans, it took 9 years
to produce cv Elf, the first commercial material. Extrapolating to beans,
it seems likely that yield increases will come slowly, and will reflect the
accumulation of effects of various modifications in cultivars and crop
management (Table 10).





13





Another worry is that the improved materials may only produce well in the
most favorable environments. This is illustrated by comparison of
hypothetical cultivars grown under optimal and stress conditions (Fig. 9).
Obviously, we still do not know if a given stress -will produce a relatively
greater or lesser yield reduction in comparison to traditional cultivars.


JlWW/pz










REFERENCES

Adams, M.W. 1967. Basis of yield component compensation in crop plants
with special references to the field bean, Phaseolus vulraris. Crop
Sci. 7:505-510.

---- 1973. Plant architecture and physiological efficiency in the field
bean. p. 266-278. In Potential in field beans and other food legumes
in Latin America. CITA, Call, Colombia.

Chandler, R.F. 1968. Plant morphology and stand geometry in relation to
nitrogen. p. 265-289. In J.D. Eastin, et al. (eds.). Physiological
aspects of crop yield. ASA, CSSA; Madison, Wisconsin.

Chandra Babu, R., P.S. Srinivasan, N. Natarajaratnam and S.R. Srce
Rangasamy. 1985. Relationship between leaf photosynthetic rate and
yield in blackgram (Vipna mungo (L) Hepper) genotypes.
Photosynthetica 19:159-163.

Charles-Edwards, D.A. 1982. Physiological determinants of crop growth.
Academic Press; Sydney. 161 pp.

Cooper, R.L. 1985. Breeding semi-dwarf soybeans. Plant Breeding Reviews
3:289-311.

Donald, C.M. 1968. The breeding of crop ideotypes. Euphytica 17:385-403.

Duncan, W.G. 1968. Cultural manipulation for higher yield. p. 327-342.
In J.D. Eastin, F.A. Haskins, C.Y. Sullivan and C.H.M. Van Bavel
(eds.). Physiological aspects of crop yield. ASA,CSSA; Madison.

Evans, L.T., I.F. Wardlaw and R.A. Fischer. 1975. Wheat. p. 101-149. In
L.T. Evans (ed.). Crop physiology: Cambridge University Press;
London.

Gale, M.D. and S. Youssefian. 1985. Dwarfing genes in wheat. p. 1-35.
In G.E. Russell (ed.). Progress in plant breeding. I. Butterworths;
London.

Gifford, P.M. and L.T Evans. 1981. Photosynthesis, carbon partitioning
and yield. Ann. Rev. Plant Physiol. 32:485-509.

Gray, R.C. and G.W. Akin. 1984. Foliar fertilization. p. 579-584. In
R.D. Hauck (ed.). Nitrogen in crop production. ASA, CSSA, SSSA;
Madison.

Jennings, P.R. 1968. Morphology, stand geometry, nitrogen-discussion, p.
286-287. In J.D. Eastin, F.A. Haskins, C.Y. Sullivan and C.H.M. Van
Bavel (eds.). Physiological aspects of crop yield. ASA, CSSA;
Madison.










---- and J. de Jesus Jr. 1968. Studies on competition in rice. I.
Competition in mixtures of varieties. Evolution 22:119-124.

Kertesz, Z. 1984. Improvement of harvest index. p. 93-104. In W.
Lange, A.C. Zeren and N.G. Hogenboom (eds.). Efficiency in plant
breeding. PUDOC; Wageningen.

Kramer, T. 1984. Harvest index and grainyield as selection criteria in
plant selection, p. 109-112. In W. Lange, A.C. Zeren and N.6.
Hogenboom feds.). Efficiency in plant breeding. PUDOC; Wageningen.

Kueneman, E.A., D.H. Wallace and P.M. Ludfor. 1979. Photosynthesis
measurements of field-grown dry beans and their relation to selection
for yield. J. Amer. Soc. Hort. Sci. 104:480-482.

Laing, D.R.L., P.G. Jones and J.H.C. Davis. 1984. Common bean (Phaseoius
vulqaris L.). p. 305-351. In P.R. Goldsworthy and N.M. Fisher
(eds.). The physiology of tropical field crops. John Wiley & Sons;
New York.

Lugg, D.G. and T.R. Sinclair. 1981. Seasonal changes in photosynthesis of
field-grown soybean leaflets. 2. Relation to nitrogen conten.
Photosynthetica 15:138-144.

Molina C, A. 1986. Efecto de la distancia entire surco sobre el rendimiento
en grano y otros parAmetros fisiol6gicos de cuatro cultivares de
frijol precoz (Phaseolus vulqaris L.). Ing. Agr. Thesis, Universidad
Nacional, Palmira, Colombia.

Nienhuis, J. and S.P. Singh. 1986. Combining ability analyses and
relationships among yield, yield components, and.architectural traits
in dry bean. Crop Sci. 26:21-27.

Sinclair, T.R. and C.T. de Wit. 1976. Analysis of the carbon and nitrogen
limitations to soybean yield. Agron. J. 68:319-324.

Tanaka, A. and K. Fujita. 1979. Growth photosynthesis and yield
components in relation to grain yield of the field bean. J. Fac. Agr.
Hokkaido Univ. 59(2):145-238.

Wallace, D.H. 1973. Commentary upon: plant architecture and
physiological efficiency in the field bean. p. 287-295. In
Potential of field beans and other food legumes in Latin America.
CIAT, Cali, Colombia.

White, J.W. 1981. A quantitative analysis of the growth and development
of bean plants (Phaseolus vul! aris L.). Ph.D. thesis. University of
California; Berkeley.








Table 1. Expected direct gain (data in diagonal) and correlated gains under selection" (combined in
two locations) for yield and its components in beans.



Selection criteria Yield Pods/mn Seeds/pod Seed weight
(g/m=) (g/100)



Yield (g/m2) 5.77 -2.28 1.57 6.46

Pods/m2 -2.67 5.06 -6.54 -1.85

Seeds/pod 1.41 -5.04 10.01 -3.3

Seed weight (a/100) 6.84 1.67 -3.89 12.83

Mean performance 147.10 155.70 4.05 23.50


SPercent of mean of characteristic.
Direct gain = k 62, / 6,,p correlated gain = k Cova 12 hi02,2








Table 2. Correlations between yield and harvest index, biomass,
duration in various studies at CIAT.


days to maturity, and leaf area


Harvest Days to Foliar area
Trial index Biomass maturity duration Source



10 lines
Habits 1 y 2 0.51 0.94** 0.75** 0.88** White, 1981

38 lines
Habits 1 y 2 0.46** 0.87** 0.41** 0.42** White, 1981

Porrillo Sintetico
12 trials 0.28 0.96** 0.85** 0.87** Laing et al., 1984

9 grain legume
species 0.50 0.91** 0.86** 0.93** Laing et al., 1984


*, significant at the p = 0.05 and p = 0.01 levels, respectively.










Table 3. Increase in leaf photosynthetic rates in beans reported since
1962.



Author' Year Rate


mg CD2.dm-2.h-'


Gaastra 1962 22
Hesketh & Moss 1963 12
!zhar & Wallace 1967. 15
Austin & MacLean 1972 24
Fraser & Bidwell 1974 19
Louwerse & Zweerde 1977 22
Tanaka & Fujita 1979 35
El-Sharkaway et al. 1985 35




SFor complete citation of references not listed in the bibliography see
White, 1981.










Table 4. Yields and days to maturity of 8 lines orown under natural (12.5
hours) and extend (13.5 hours) photoperiods, with or without
trellising.
Source: Masaya, not published.



Photoperiod (hours) __
12.5 13.5
Days to Days to
Cultivar Yield maturity Yield maturity


kg.ha-'


kg.ha-I


Without trellis:


BAT 450
DOR 49
6 2959
6 3807
G 17648
JU 78-12
JU 80-13
XAN 112


2338
2335
2333
1590
1550
2185
2046
2038

2052


Mean


2439
2398
2307
1785
1236
1985
2225
1686

2008


With trellis:

BAT 450
DOR 49
6 2959
6 3807
6 17648
JU 78-12
JU 80-13
XAN 112


2115 80


2324
2304
1912
1731
1882
2694
2073
2043


2598
2381
2800
1562
2913
3200
2121
2106


2460 82


Mean











Table 5. Comparison of photoperiod response in relation to yield and days
to maturity for promising late maturing lines. Palmira 1984b.


Number of lines with response toohtoperiod
Neutral Intermediate Sensitive


Yield (kg/ha)


< 1500


1500-2000


> 2000


Chi2 = 10.7 p .005


Days to maturity


< 82

82-86

> 86


Chi2 = 7.1 p .05






Table 6. Mean yields from seed of F4 progenies derived from individual selections performed in the
F2 using various selection criteria: HI = harvest index, DW = plant dry weight; DY =daily
yield. Numbers in parenthesis indicate F2 plants in a given category.
Masaya, personal communication.



Selection criteria
Criterion
Parental yield 1 2 3 4 4 plus
Cross Female Male HI DW DY VS 1+2 1+3 2+3


------------------------------------- g.plot-i.----------------------------------


A 429 x 268 256 266 312 283 270 287
XAN 112 (20) (10) (3) (62) (13)


A 429 x 268 259 258 e 286 269 258 317
Pata de ZoDe (16) (9) (23) (2) (4)


A 429 x 268 285 253 253 263 282
Pecho Amarillo (21) (9) (128) (9)










Table 7. Effects of general combining ability for yield in various
cultivars and advanced lines evaluated at two sites in Colombia.
Source: Nienhuis y Singh, 1986.



Locality
Cultivar Palmira Quilichao


Black seeded:


A 310
A 375
A 445
BAT 58
BAT 304
BAT 477
BAT 1617
Carioca
ICA Pijao
IPA 7419
Jamapa
Porrillo Sintetico
Rio Tibagi
RIZ 11


Standard error of effects


10.9
37.6
27.4
-24.7
5.0
24.0
18.3
-17.5
0.5
-16.5
-22.7
-1.5
-12.6
8.2


47.4
26.7
15.4
5.5
-17.1
22.5
12.5
7.8
-16.0
1.8
-12.5
-26.2
9.3
40.0


Mean yield


1370


1570











Table 8. Crop dry weights (at 56 days) and yields of eight lines planted
at four distances between rows. All plots planted at 20
plants/m2.



Distance between rows (cm)
60 45 30 20


Crop dry
weight at
56 days
(g/m2)


BAT 1481
BAT 881
BAT 477
A 170
BAT 1554
G 4525
A 54
FAB 58


264
311
220
286
262
271
240
259


Mean


S.E. for difference of means of:


Yield
(kg/ha)


BAT 1481
BAT 881
BAT 477
A 170
BAT 1554
6 4525
A 54
FAT 5B


Mean


S.E. for difference of means of:


Treatment x line =
Treatment =


2370
2630
2780
2690
2570
2250
2390
2190

2480


2950
2840
2800
2720
2670
2480
2130
2450

2630


Treatment x line =
Treatment


2630
2860
2700
2760
2520
2400
2390
2150

2550


2550
2500
2300
2370
2180
2130
2100
2045

2270











Table 9. Response of yield to plantings at 0.3 m and 0.6 m between rows
with populations of 100.000 and 900.000 plants.ha-1. In
semester A,-data are for BAT 477, and in semester B, for means
of lines BAT 271, BAT 477 and BAT 881.


Distance between
row (m)


Semester A:


Population (plants.10-3.ha-1)


400


-------------------------kg.ha-I------------------------


2280
2320


2550
2300


2620
2430


2670
2350


2650
2480


Significance level of effect:


Distance
Population
Distance x population


Semester B:


----------------------kg.ha-1---------------------


1870
1900


Significance level of effect:


Distance
Population
Distance x population


2600
2410


0.05
0.05
NS


300


0.3
0.6


2190
1980


2030
1970


2150
2000


0.05
0.05
NS


- ------- ---------


--











Table 10. A plan for a progressive increase in bean yields.


Increase (in .)


Actual yield


Plus effect of:


Distance between rows

Higher populations

Resistance to lodging
Response to No


& A yield increase of 1193 kg.ha-I represents 250 kg.ha-1 more protein,
which in turn represents 18 kg.ha-1 additional N in seed, not counting
losses in material not harvested.


Yield


k g.ha-1


3000


3300
3465

3812
4193


----







300 g/m2


A Determinate

O Indeterminate


4001-
0.10


0.20


0.30

Seed weight (g)


Example of compensation between yield components in 38 lines.
represent levels of constant yield. Source: White, 1981.


The curves


1800


1600


1400


1200


1000


800


600


Figure 1.


0.40


0.50


__









0.7


0
S0


S' = 077**
(> 0
C 0.5-
S y 0.323 + 0.000128 X
R2 = 0.77**

0.4,
1000 2000 3000
Yield (kg.ha1)



Figure 2. Illustration of the problem of artificial correlations
between yield and harvest index. Data were calculated
from 20 pairs of random numbers used to represent
vegetative and ,sed weight in 20 hypothetical cultivars.




Figure 3. Bulk-pedigree method used for yield breeding at CIAT.


Month Generation Activities


Parental


Parental and Fi


January


May


C = CIAT-Palmira, P = PopayAn, 0


Intermating between selected parents


Intermating between selected parents and crosses
Save F2 seed of selected individual crosses


Grow & save F2 seed of selected crosses


Yield test of replicated trials
Save bulk F3 (SP) of selected crosses


Yield test & save bulk F4 of selected crosses


Yield test & save bulk F5 of selected crosses


Space plant for selection of invidual plants


Progeny test in replicated yield trials
Save bulk F, of selected lines


Yield test & code selected lines for National
Programs & VEF, EP, IBYAN and other nurseries


Locality


September


January



May


September


January


May



September


I


_ ~I~ ___


= Santander de Quilichao




Figure 4. Recurrent selection method proposed for yield breeding in CIAT.


Month Generation Activities Locality

C~P Itermte slectd paentsfor reedng o


January



April


July



October


January


April


July


October


January


C = CIAT-Palmira, P
* If not needed, a


CoP Intermate selected parents for breeding of
yield characters


CoFi Yield test and discard poor crosses


CoFI Intermate between selected crossis using
remnant seed (Fi)


CoFI Yield test and discard poor crosses


CoF2 Yield test.and discard poor crosses


CoF3 Space plant for. individual selection


CoF4 Yield test and discard poor families


CoFs Yield test and discard poor families


C1F, Intermate between families selected for
high yiels


= PopayAn, 0 = Santander de Quilichao
new recurrent selection cycle could be initiated in F4


C



C


C



C


CPQ*


C


C


CPQ*


C






100-
o-
90


80.


-S
.5..
-5


"--18 Dias


20 30


45


60


Distance between rows (cm)


Relation between cancpy cover and distance between
rows. Mean of four genotypes. Source: Molina, 1986.


-44 Dias




30 Dias


70-


60-


50-


40-


30-


Figure 5.





0.57













co


C'
oo



S0.25-
>

r4-

a)













0-


o .

s* *

S* *


* 5


*
0
00
I

0


)Oa 0

0 000


o 0
0 *

ao o


,
0 *.* *




S 0 0 *
*o o
0 0
00
o


I B ~_0


0.3


0.6


Relative pod weight


Relation between relative leaf and pod weights (removed plus mat ire pods) in
individual plants of G 4523 (ICA Linea 17).


Y = 0.44 0.50 X

R2= 0.63***


Figure 6.


0.9











N.
N
N
N. 30cm

N


- -


2.4-



I-
Ca

_ 2.2-

r-
2.0
i-r




2.0-


0


20


Nitrogen (kg.ha- .week-1)


Interaction of weekly applications of nitrogen (as urea,
starting 30 days after planting) and distance between rows
for mean of BAT 1481 and ICA Pijao.


60cm


Figure 7.


1 I _j

























300.000


600.000


900.000


No. of plants.ha-1


Loss of population at 0.3 m and 0.6 m between rows
for densities at thinning of 15 to 90 plants.m -2


100-


90-


80


-4


Figure 8.











0 -= Optimal management
E = Stress


0


43


0


s,--




\I
\F
\ 1


Traditional mats.


Bred materials


Hypothetical responses of.traditional and bred
materials to optimal or stress management
conditions.


Figure 9.


| n


I I







The Role of Architecture, Crop Physiology and Recurrent Selection

in Ideotype Breeding for Yield in Dry Beans

M. W. Adams and J. D. Kelly.

Crop and Soil Sciences Department

Michigan State University

SEast Lansing, MI 48824 USA



According to Donald (1968), ideotype breeding conveys the thought

that the plant breeder will conceive of some set of architectural-

morphological characteristics in a given crop plant which, in a

particular agro-ecologic setting, would be expected to produce maximum

yields. The ideotype is an idealized plant model; it does not exist

initially except in the mind of the breeder.

In ideotype breeding, the breeder maybe likened to the architect-

builder. A design must first be conceived, a set of blueprints drawn,

and then the building constructed. Hopefully, the building will be both

attractive and functional, and appropriate for the site and community in

which it is located.

In present usage, breeding to a yield ideotype requires the breeder

to consider not only morphological-architectural characteristics but

crop physiological attributes as well, and since the breeder is also the

"builder," there is required an understanding of- the genetics of the

various characteristics, their interactions with each other and the

environment, and a strategy for bringing the various component parts

together into a single genotype. Our paper will follow this general

outline.







Critics may question this strategy, in preference to the more

traditional approach of "crossing the best with the best, and selecting

the best." While some progress in yield may result from this approach,

we feel that the procedure is more mechanical than creative since it

does not take advantage of what may be known of the morphological and

physiological determinants of yield. Thus the best yield achievable

will be less than that which is potential in the species as a whole were

morphological-physiological information to be exploited.

The fundamental architectural objectives in bean yield design were

previously identified (Adams, 1982) to be:

1. a leaf-stem canopy capable of intercepting all incident light,

by absorbing, scattering, and transmitting the

photosynthetically active radiation throughout the plant

profile.

2. to construct the canopy so that the profile consists of as many

source-sink units (leaf, internodal section, node, and auxiliary

raceme) as possible and feasible, and

3. to make each unit as functionally efficient as possible,

through:

a. adjustment of the source to sink ratio to maximize pod and

seed number and single seed size relative to leaf size, and

b. the source leaves being displayed in such a way as to

intercept light sufficient for a high rate of

photosynthesis, without seriously occluding leaves located

lower in the plant or crop profile.

These objectives are general enough to cover plant ideotypes for

several agro-ecologic conditions. For the small-seeded navy (white)




- J -


bean to be grown as a monocrop under optimal soil and climatic

conditions in the mid-continental U.S., we have translated these

objectives into a specific set of architectural characteristics, which

we call an "architype," and have given the statistical data which

support the architype as a high yield ideotype (Adams, 1973, 1982). A

number of superior-yielding navy and black-seeded varieties (Table 1)

have been produced, based upon the architype model (Adams et al. 1986,

Kelly et al. 1984).

Architecture, in and of itself, however, does not guarantee high

yield. Morpho-architectural characteristics must be associated without

strong adverse relationships to yield, and moreover, must be combined

with yield-promoting crop physiological attributes, which were alluded

to in our earlier ideotypes, but now need to be specifically enunciated,

insofar as there is experimental evidence for their inclusion in a

breeding program.

It should be evident that seed yield is the integration of seed

growth rate per unit of land area over the time period of seed

filling. It might seem logical, therefore, to include both seed growth

rate (SGR) and seed filling duration (SFD), or effective filling period

(EFP) as ideotype traits, and to select for these traits in the breeding

program. But first we must ask to what extent in beans these traits are

correlated with yield or any of the components of yield, and how they

are correlted one with the other.

Paredes (1986), studying 12 cultivars of common beans varying in

plant type, seed type, maturity and yield, found significant differences

in both rate and duration of seed-filling. Mean filling rate, however,

was highly negatively correlated with number of pods/square meter,







number seeds/pod, seed yield, bioyield, and days to physiological

maturity. The linear filling period (major component of EFP), on the

contrary, was highly positively correlated with those same

characteristics. Clearly, SCR and SFD are inversely related to each

other in the data of Paredes (1986); in selecting for a high SGR, one

would select in a secondary way for a reduced duration of filling.

Izquierdo (1984) had previously shown this inverse relationship in the

two strains, NEP-2 and Black Turtle Soup. These observations were based

upon the performance of specially selected strains and released

varieties, and it cannot be assumed that the same relationships would

necessarily prevail in large unselected populations of lines.

Nevertheless, no exceptions to this relationship were found among F3 and

F4 families produced by single seed descent from the cross of NEP-2 by

Black Turtle Soup (Adams 1974, unpublished observation).

A recent paper by Salado-Navarro et al. (1986a) in soybeans

summarizes experiments which, in toto, present a somewhat inconsistent

picture as regards SGR and SFD in that crop. High yields may be

obtained in varieties with low SCRs, and varieties with different yields

could display similar SCRs. Varieties with similar yields exhibited

significant differences in SGR. Only small fractions of yield variation

among field-grown random soybean genotypes could be explained by linear

regression upon estimates of seed filling duration. Nevertheless, in

simulated genotypes, Salado-Navarro et al. (1986b) found that highest

yield was achieved by a genotype with the greatest biomass at the

beginning of seed growth, highest potential crop growth rate, and the

lowest dry matter allocation coefficient (DMAC, this being defined as

the rate of linear increase of the harvest index) which resulted in a







high SGR and the longest seed filling duration. DMAC, when high,

reflects a rapid withdrawal of C- and N-assimilates from vegetative

organs and transport to seeds, resulting in early senescence of leaves

and a strongly limited seed filling duration. When effective filling

period is determined as the final seed weight divided by the seed growth

rate, it is obvious that an inverse relationship between SCR and EFP

will be found. Sinclair (in Salado-Navarro, et al., personal

communication, 1986) believes that in unselected populations, where

there is genetic variability for both SGR and EFP, genotypes will occur

in which high levels of both parameters will be present.

In Izquierdo's (1981) data on nine bean cultivars, the length of

effective filling was positively and significantly correlated with

seeds/pod, number seeds/square meter, and yield. The linear seed

filling rate was significantly negatively correlated with seeds/pod, and

negatively but not significantly correlated with seeds/square meter, and

with yield. The top-yielding entries, however, were those with the

longest effective filling periods and with high, but not highest, linear

filling rates. These Type II architypes have since been released as

commercial cultivars in Michigan, where they continue to yield from 15

to 30% above standard determinate navy beans. These varieties and

subsequently released architypes not only yield well but display

superior yield stability over locations and years. (Table 2)

On the weight of simple logic and the accumulating experimental

evidence, it is clear that, in addition to morpho-architectural traits,

certain crop physiological characteristics should be considered in a







high yield ideotype. These characteristics include the following:

seed growth rate,

longer effective filling period,

biomass at the beginning of seed filling, and

a high partitioning coefficient or harvest index.

It must be recognized that these traits may not be genetically or

developmentally independent of other traits, including the architectural

ones. High partitioning without high initial biomass will not lead to

high yields unless photo-assimilate production during seed filling is

extraordinarily high.

It should be apparent in all of the considerations concerning this

topic that there can be numerous alternative routes to high yield.

Highest yields, however, would only be possible when all components were

combined at their maximum levels. Since this may be impossible from a

practical standpoint for reasons of genetic and/or developmental inter-

dependency, we as breeders should probably strive for optimum levels of

combinations rather than maximal levels.

These crop physiological parameters, if they are to be used

successfully by bean breeders, must be shown to be heritable in the

additive genetic sense, and must be capable of being accurately

estimated in breeding populations. In beans, only limited data on the

extent of genetic control are available. In a diallel cross of six dry

bean genotypes differing in plant type, seed type, and the seed-filling

traits, Paredes (1986) showed general combining ability effects to be

significant and predominant for total filling duration, linear filling

duration, mean filling rate and seed weight. General combining ability

variance in linear filling rate failed to reach significance in his data






because of the large error associated with its estimation. The large-

seeded entry, Harris Great Northern, displayed the largest positive

general combining effect for rate of seed filling among the six parental

genotypes studied by Paredes.

On this limited evidence in beans, but consistent with evidence

from other grain crops, it may be tentatively concluded that additive

genetic control may be expected for these seed filling

characteristics. Biomass at flowering and harvest index are also known

to be moderately heritable.

The major problem related to their use in a selection program

derives from the ease--or lack of ease--of estimation of the metrical

values.of the traits. Suffice it to say, without arguing the point,

that reliable estimates will require data from replicated plots in

advanced generations of a cross. Non-replicated single plant estimates

will be essentially worthless for these characteristics.

In a breeding program designed to combine numerous traits with

differing genetic inheritance patterns from various genetic sources into

a single genotype, traditional breeding procedures for improvement of

self-pollinated crops are limiting. There exist certain obvious basic

defects in the system of conventional repetitive pedigree cycling of a

two parent cross commonly used in the breeding of self-pollinated

crops. The major limitation is that genetic variability and

recombination potential are low because of the initially restricted gene

pool and the selfing process which limits genetic recombination. If a

complete reassortment of parental genes is preferred, there is only a

limited opportunity for that to occur with self-fertilization. Since

the more common systems for improvement of self-pollinated crops, such







as mass, pedigree, and modified bulk (single seed descent) selection

procedures, do not permit adequate genetic recombination, Jensen (1970)

proposed the diallel selective mating (DSM) system. Because the DSM

system involves intermating F1 and F2 individuals without target trait

selection, Bos (1977) compared it to the effect of random intermating of

F2 plants which he showed was negative in the F3 generation. Pederson

(1974) showed that intermating within an F2 population from a cross of

two homozygous parents will only be of benefit'for two loci if the

alleles are linked initially in the repulsion phase. If loci are spread

over three or more chromosomes then the expected gain from intermating

is consistently small. Hanson (1959) suggested that recombination may

be promoted by an initial round of intermating commencing at the F2

generation and he concluded from a study of the breakup of linkage

blocks that a breeding program for a self-pollinated species should

include at least one and preferably three or four generations of

intermating if at all feasible. Other strategies to improve genetic

recombination in self-pollinated crops have been used in soybeans, where

Thorne and Fehr (1970) showed that genetic variance for yield in 3-way

populations was larger than in 2-way populations. The 3-way cross

produced a greater number of superior lines for yield and was a better

avenue for introduction of exotic germplasm into soybean cultivars.

Other systems, such as recurrent mass selection which should favor

genetic recombination, have been employed by Sullivan and Bliss (1983)

to simultaneously increase seed yield and seed protein in beans. The

seed protein was increased after two cycles of selection whereas mean

seed yields were not. Sullivan proposed the use of a selection index

for the seed yield trait but the study was restricted by the small size







of populations used and the limited number of cycles examined. Fehr and

Ortiz (1975) used recurrent selection for yield in soybean and showed S1

selection to be more efficient assuming SI testing for yield is based on

one cycle per year whereas S4 testing would require two years. Compton

(1968) proposed a.system of recurrent selection in self-pollinated crops

which would minimize crossing by advancing only descendants of a

different F1 rather than from different F2 plants within an Fl. The

limitation of many recurrent selection schemes for yield is the

requirement for elaborate data collection if selection indices are used

or when S1 selection is practiced for yield. The latter selection

procedure requires the use of numerous hill plots and hill plot planting

arrangements which are not easily mechanized. The time consuming nature

of planting and data collection reduces the size and numbers of

populations that can be handled effectively, and so.reduces the

efficiency of the system.

Evidence from the breeding program at MSU (Figure) indicates, for

small-seeded beans, that the architype offers the most favorable

combination of traits positively associated with yield, suggesting that

the obvious strategy for yield improvement in other seed types (Kelly et

al. 1987) would be the development of architypes in the different

commercial classes. Since the architectural component of the yield

complex is highly heritable and highly visible, its choice as the most

favorable trait for selection in a segregating population is obvious.

Thus a system of phenotypic recurrent selection (PRS) where recombinant

individuals can be easily identified in large populations, selected in

the S1 generation and intermated as S2 individuals, permitting a cycle

per year, offers the best opportunity for efficiency. The advantage of




- lU -


intermating S2 plants is that the alleles are not homozygous at all loci

and so permits more genetic recombination than intermating lines

homozygous at all loci. This has the disadvantage that the selected

single plant phenotype may not accurately reflect a superior genotype

for use in the intermating of S2 individuals for the establishment of

the next cycle. This is the case particularly for the crop

physiological traits, if the breeder were to attempt to select for them

independently and individually. In our architype selection program with

small-seeded genotypes, favorable combinations of the physiological

traits seemed to be associated with the desired architecture, with the

result that selection for architectural form achieved acceptable levels

of physiological characteristics simultaneously.

The success of the PRS system will depend on the ability to make

sufficient numbers of crosses with the reproductive potential of

producing large recombinant populations. It will be crucial that

desired genes, initially held in unfavorable linkages, be released

through recombination and re-assembled into genic associations that

promote the levels of phenotypic performance sought in the ideotype.

This process will be aided by intermating of S2 individuals but more

importantly it will depend upon the nature of the genetic homology

between the original germplasm sources. Singh and Gutierrez (1984) have

identified an apparent incompatibility between small and medium to large

seeded germplasm sources which is controlled by two complementary

dominant genes. The genes have been implicated in limiting free genetic

recombination between the two germplasm sources and would seriously

effect a breeding system designed to maximize genetic recombination.

Gepts and Bliss (1985) have shown that there exist multiple regions of




- 11 -


domestication of dry beans and he has catalogued the diverse regions

using the major bean storage protein, phaseolin, as a genetic marker.

Beans from the Mexican center display a Sanilac (S-type) banding pattern

while lines from the Andean center produce a Tendergreen (T-type)

banding pattern with disc gel electrophoresis. All reports in the

literature indicate that genetic lethality in bean hybrids occurs when

crosses are made between lines from the different centers displaying

either the S or T-type protein markers. The lack of complete

compatibility among parents from diverse centers of domestication could

adversely affect the outcome of a system where free genetic

recombination needs to be obtained. Nienhuis and Singh (1986) indicated

that many of the high yielding small-seeded Central American cultivars

have negative CCA (Ceneral Combining Ability) for yield in combinations

with large-seeded germplasm. In addition to genetic incompatability and

F1 hybrid weakness in many crosses between these classes, CIAT has

encountered difficulties in developing large seeded types with high-

yielding ability (Research Constraints at International Agricultural

Research Centers 1986). The origin and behavior of the two seed size

classes suggest the possibility that chromosomal structural differences

exist between the two types limiting the random association of useful

characteristics other than the narrow genetic exchange possible through

a rigid backcrossing program. Since a lack of homology between the

high-yielding small-seeded architypes and the large seeded classes

appears to result in unfavorable genetic recombinations, only an

organized cyclic improvement system offers the opportunity to permit

adequate random genetic interchanges.




1L. -


In conclusion, a point is reached where it is desirable to merge

divergent gene pools in order to broaden the range of genetic

variability or introduce particular genetic effects into a self-

fertilizing crop species. There exists in such cases a strong

likelihood of encountering linkage barriers. Mather (1973) hypothesized

that long term assortment and recombination with selection within a

given gene pool will have given rise to specific adaptive and

functionally-integrated or "relationally-balanced" gene blocks.

Different gene pools, if they have been genetically isolated for a long

period of time, will form qualitatively different relationally-balanced

gene blocks. When such divergent gene pools are merged by crossing, the

breeder must expect initially to encounter a "linkage-freeze" upon free

and random recombination for effects regulated by genes in the

integrated linkage segments. With subsequent generations of

intercrossing and selection, the linked effects should reassemble into

new combinations, among which some should be favorable in a selection

sense. The experience at MSU (Kelly and Adams 1987) with the

architectural components associated with the type-II plant type and the

seed size factors associated with the type-III pinto gene pool is

consistent with this expectation. It is interesting that qualitative

factors like seed color and mottling genes recombined freely in the

first segregating generations, but the major genes affecting

architecture and seed size did not recombine until the third cycle of

recurrent selection.

A breeder rarely possesses a "read-out" of the genetic organization

of the targeted effects in divergent gene pools prior to undertaking the

crossing and selection process. It is particularly noteworthy that the







system of phenotypic recurrent selection as described in this case has,

over time, proved effective in breaking and re-assembling a small number

of functionally integrated linkage blocks. The medium-seeded pinto

architypes resulting from our program (Kelly and Adams 1987) can now be

used as a bridge for the improvement of architectural characteristics of

other medium seed-sized commercial classes, such as great northern,

pinks, red mexicans, canaries, and bayos. The highly heritable nature

of the architecture super-gene block should permit the easy recovery of

these characteristics without the associated problems of linkages with

small seed size.




- 14 -


Literature Cited



Adams, M.W., 1973. Plant architecture and physiological efficiency.

In: Potentials of field beans and other food legumes in Latin

America. Centro Internacional de Agricultura Tropical, Cali,

Colombia. pp. 226-278.

Adams, M.W., 1982. Plant architecture and yield breeding in Phaseolus

vulgaris. Iowa State J. Res. 56:225-254.

Adams, M.W., A.W. Saettler, G.L. Hosfield, A. Ghaderi, J.D. Kelly, and

M.A. Uebersax, 1986. Registration of 'Swan Valley' and 'Neptune'

navy beans. Crop Sci. 26:1080-1081.

Bos, I., 1977. More arguments against intermating F2 plants of a self-

fertilizing crop. Euphytica 26:33-46.

Compton, W.A., 1968. Recurrent selection in self pollinated crops

without extensive crossing. Crop Sci. 8:773

Donald, C.M., 1968. The breeding of crop ideotypes. Euphytica 17:385-

403.

Fehr, W.R. and L.B. Ortiz, 1975. Recurrent selection for yield in

soybeans. J. Agr. Univ. P;R. 9:222-232.

Gepts, P. and F.A. Bliss, 1985. F1 hybrid weakness in the common

bean. J. Heredity 76:447-450.

Hanson, W.D., 1959. The breakup of initial linkage blocks under

selected mating systems. Genetics 44:857-868.

Izquierdo, J.A. 1981. The effect of accumulation and remobilization of

carbon assimilate and nitrogen on abscission, seed development, and

yield of common bean (Phaseolus vulgaris L.) with differing

architectural forms. Ph.D. thesis. Michigan State Univ. 188 pg.







Jensen, N.F., 1970. A diallel selective mating system for cereal

breeding. Crop Sci. 10:629-635.

Kelly, J.D., M.W. Adams, A.W. Saettler, C.L. Hosfield and A. Chaderi,

1984. Registration of C-20 navy bean. Crop Sci. 24:822.

Kelly, J.D. and M.W. Adams, 1987. Phenotypic recurrent selection in

ideotype breeding of pinto beans. Euphytica 36(1): in press.

Kelly, J.D., M.W. Adams, A.W. Saettler, G.L. Hosfield, M.A. Uebersax and

A. Ghaderi, 1987. Registration of 'Domino' and 'Black Magic'

tropical black beans. Crop Sci. 27(2): in press.

Mather, K., 1973. (ed.) In Genetical Structure of Populations. Chapman

& Hall Publ. London (pp. 197).

Nienhuis, J. and S.P. Singh, 1986. Combining ability analysis and

relationships among yield, yield components, and architectural

traits in dry beans. Crop Sci. 26:21-27.

Paredes-Carcano, O.M. 1986. A study of seed filling and dry matter

partitioning characteristics and their combining ability effects and

relationship to yield among dry beans with differing growth habits,

architecture and maturities. M.S. thesis. Michigan State Univ.

184 pg.

Pederson, D.G., 1974. Arguments against intermating before selection in

a self-fertilizing species. Theor. Appl. Genet. 45:157-162.

Salado-Navarro, L.R., T.R. Sinclair and K. Hinson, 1986a. Yield and

reproductive growth of simulated and field-grown soybean. I. Seed

filling duration. Crop Sci. 26:966-970.

Salado-Navarro, L.R., T.R. Sinclair and K. Hinson, 1986b. Yield and

reproductive growth of simulated and field-grown soybean. II. Dry

matter allocation and seed growth rates. Crop Sci. 26:971-975.




- 16 -


Singh, S.P. and J.A. Gutierrez, 1984. Geographical distribution of the

DLl'and DL2 genes causing hybrid dwarfism in Phaseolus vulgaris L.,

their association with seed size, and their significance to

breeding. Euphytica 33:337-345.

Singh, S.P., 1982. A key for identification of different growth habits

of Phaseolus vulgaris L. Ann. Rept. Bean Impr. Coop. (New York).

25:92-95.

Sullivan, J.G. and F.A. Bliss, 1983. Recurrent mass selection for

increased seed yield and seed protein percentage in the common bean

(Phaseolus vulgaris L.) using a selection index. J. Amer. Soc.

Hort. Sci. 108:42-46.

Thorne, J.C. and W.R. Feher, 1970. Exotic germplasm for yield

improvement in 2-way and 3-way soybean crosses. Crop Sci. 10:677-

678.




- 17 -


Table 1. Seed color and size characteristics, growth habit and
center of domestication of twenty-eight dry bean cultivars
representing seven commercial seed classes.


Commercial Seed Hundred Growth' Center
seed coat seed habit of
Cultivar class color weight domestication
(g)


Seafarer
Midland
Wesland
Fleetwood
Laker
Bunsi
C-20
Swan Valley
Neptune
Aurora
Midnight
Domino
Black Magic
T-39
Black Beauty
Montcalm
Charlevoix
Isabella
*Redkloud
Sacramento
Linden
Taylor Hort
Cran-028
Michicran
Ouray
Olathe
Pindak
Rufus


Navy
Navy
Navy
Navy
Navy
Navy
Navy
Navy
Navy
Small White
Black
Black
Black
Black
Black
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Cranberry
Cranberry
Cranberry
Pinto
Pinto
Pinto
Red Mexican


White
White
White
White
WNite
White
White
White
White
White
Black
Black
Black
Black
Black
Dark Red
Dark Red
Light Red
Light Red
Light Red
Light Red
Red Mottled
Red Mottled
Red Mottled
Brown Mottled
Brown Mottled
Brown Mottled
Red


*1
I
I

I
II
II
TI
II
II
II
II
II
II
ZI
II
I
I
I
I
I

I

I
III
II
III


Meso-American
Meso-American
Meso-American
Meso-American
Meso-American
Meso-American
Meso-American
Meso-American
Meso-American
Meso-American.
Meso-American
Meso-American
Meso-American
Meso-American
Meso-American
Andean
Andean
Andean
Andean
Andean
Andean
Andean
Andean
Andean
Meso-American
Meso-American
Meso-American
Meso-American


tGrowth Habit I = determinate, II = indeterminate upright short
vine, and III = indeterminate prostrate long vine, Singh (1982).




- io -


Table 2. Days to maturity, mean
coefficient (b) and standard error 4Sb),
and coefficient of determination (r~) of


seed yield, regression
deviation mean square (S2)
28 dry bean cultivars from


42 trials conducted in Michigan during 1980-1985.


Days Seed
Cultivar to yield b s sb r
maturity (kg/ha)


Seafarer
Midland
Wesland
Fleetwood
Laker
Bunsi
C-20
Swan Valley
Neptune
Aurora
Midnight
Domino
Black Magic
T-39
Black Beauty
Montcalm
Charlevoix
Isabella
Redkloud
Sacramento
Linden
Taylor Hort
Cran-028
Michicran
Ouray
Olathe
Pindak
Rufus


85
89
94
97
104
95
98
105
102
93
97
97
97
93
100
96
96
86
88
84
105
85
99
99
85
88
90
97


2004
2168
2336
2530
2494
2472
2734
2538
2572
2131
2717
2695
2729
2598
2593
2095
2184
2148
1990
1938
2165
2136
2445
2199
2116
2537
2734
2638


0.93
1.01
1.03
0.84
1.00
0.85
1.06
1.27
1.35
0.69
1.18
1.20
1.27
1.07
1.25
0.82
0.96
0.87
0.94
0.78
0.79
1.02
0.76
0.88
0.84
0.99
1.23
0.93


0.082
0.077
0.098
0.102
0.128
0.120
0.096
0.103*
0.105**
0.082**
0.078*
0.071**
0.074**
0.090
0.115*
0.114
0.106
0.202
0.183
0.185
0.211
0.135
0.193
0.115
0.143
0.121
0.116
0.216


56537
46897
68256
88261
121670
102998
74181
76073
62224
53899
56964
45632
29461
62546
75787
114527
99652
211549
212024
271535
211847
142291
152005
113569
100064
114152
84265
270596


0.79
0.84
0.79
0.66
0.67
0.62
0.78
0.83
0.89
0.68
0.86
0.89
0.94
0.81
0.84
0.60
0.71
0.46
0.48
0.36
0.39
0.66
0.48
0.62
0.60
0.69
0.82
0.42


Mean 2380
*,** Significantly different
levels, respectively.


from b=1.0, at the


0.05 and 0.01






- 19 -


YIELD


S STA.. LITF' PA :^ 'A M1 ETECR
COMPARISON OF 28 BEAN GENOTYPES


3.20
3.00
2.80
2.60


2.20

2.00
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00


SEED SIZE & PLANT HABIT
1 YIELD KG/HA = EMS'100


SS-I = Small-seeded, Type-I;

AB-II = Aurora, Bunsi, Type II;


LS-I = Large-seeded, Type I; ARC-II = Architype, II;


Type III = Medium-seeded, Type III.


SLS-I A-1 AE- I
SS-i LS--! ARC-I! AE--I TYPE-Il1








Heri tabi cities and FPhnotypi .:: Correlations for Seed Yield and
Yield Compornents. of Bean Popul] at ons Derived from Crosses
bet.wr'(:e D-etermi late anid Indetermi nate Genotypes


I'. Mateo Solano, J.S. Beaver, and F. Saladin Garcia 1/


INTRODU CTI ON

In spite of the f ac.:t tliat. climatic: and edaphic conditions di f er

r!-:at1ly f or b eainls gro own in the Domiinic an Republ]ic, -farmers tend to

-:. the same groa.upf of c.u:i t vars 4or all plantings. 1 here ore, in

-der toC be succ:essf u], bean cultivars need to be capable of

.oducingi predictable yields over a wide range of environmental

--nlditions. Result ts from -field trials conducted on small farms and

:r periment stations in the Dominican Republic found determinate,

-rd-rmottled bean cultivars to have lower and less predictable

fields than indeterminate, small-seeded genotypes ( 2 ). In an

-ttempt to improve the yield level. and stability of beans in the

o-.miniican Republ ic, a plant breeding program was initi-atec to

ovelop erect, indeterminate bean genotypes with seed size and

--_ed characteristics acceptable to the Dominican.consumer. Crosses

.--tween large-seeded, determinate and small-seeded, indeterminate

_. e*an g.enotypes can result in genetic dwarfs (5,10) which, perhaps,

:\'e discouraged bean breeders from making wide crosses. Nienhaus

.7d1 Singh (8) note that the design of effective selection

--- ocedCures to simultaneously increase yield and seed size depends




Former graduate r research assistant and associate
*-,ofessor, respectively, D ep. of Agronomy and Soils, Univ. of
.errto Rico, Mayaguez Campus, Mayaguez, Puerto Rico (00708 and
-incipal investigator Bean/Cowpea CRFSF Project, Secretaria de
:.t.ado de Agricultura, Santo Domingo, Dominican Republic








on the knowledge of the inheritance of yield and its components

and also on an understanding of the strength and stability of the

relationships among these traits.' The objectives of the research

were : 1) determine the yield potential and describe the yield

components of indeterminate F. lines derived from crosses between

mcdi num to large-seeded determinate and small-seeded

i ndetermi nate bean genotypes, 2) determine the effect of

productivity of environment on the expression of yield

components, .) determine the strength and stability of the

relationship of yield components with yield, and 4) estimate the

narrow sense heritabilities of seed yield and its components.


MATERIALS AND METHODS


Six bean populations derived from crosses between medium to

large-seeded determinate and small-seeded indeterminate bean

genotypes were used in the study. The medium to large-seeded,

determinate genotypes used in the study were Pompaduor checa,.Jose

Beta, 8241-168A, and Borinquen. The small-seeded, indeterminate

genotypes used in the study were H-376, La Vega, and PAI 92. The

F, generation of the populations was planted in blocks at the

Fortuna Agricultural Research and Development Center (ARDC), Juana

Diaz, Puerto Rico on 20 October 1984. Rows were spaced 60 cm apart

and-the spacing among plants within a row was approximately 10 cm.

At harvest maturity, 50 plants were selected at random from each

block. Seed yield and its components were measured. Seed yield

was measured as seed weight per plant. Seed size was measured as

the weight of 100 seeds. Number of pods was measured on a per





plant basis. Number of seed per pod was estimated by dividing the

number of seed per plant by the number of pods per plant.

A total '50 F_ plant rows of each population were.planted on 22

Feburary 1905 at the Fortuna ARDC and on 22 March 1985 on a small

farm in the El Rio parish, Constanza, Dominican Republic. A

replications within blocks design was utilized (6). The experiment

consisted of 5 blocks with 3 replications within each block. Each

replication of a block consisted of 10 F. lines selected at random

from a population and the two genotypes used as the parents to

create the population. The experimental units consisted of ten

seeds planted in 1 m row lengths spaced 0.6 m apart. Two bordered

F, plants having the same growth habit as the plant from which

they were derived were selected from each row. Seed yield and its

components were measured utilizing the previously described

methods.

Seed yield and yield component means of the indeterminate F3

lines and their parents were determined for each population and

location. Means of the F3 lines and their parents were compared

using an approximate t test. Fhenotypic correlations between seed

yield and the yield components were.calculated for each population

and location using the means of the indeterminate F_ lines. Narrow

sense heritabilities were estimated for each population _and

location by regression of means of F, lines onto individual F,
2

plant measurements. Spearmnan rank correlations between locations

were calculated using F. means.








RESULTS AND DISCUSSION


Seed yield per plant of the indeterminate F, lines were

generally significantly less than the seed yield per plant of

their indeterminate parents (Table 1). The differences between

the means of the F, lines and the means of the indeterminate

parents were particularly large in the low yield environment,

Constanza. These results indicate that the evaluation of large

popu atiorns may be necessary in order- to identify F: lines with

yield potential similar to the indeterminate genotypes used as

parents in this study. Moreover, it may not be possible to

identify indeterminate F, lines with adequate yield potential from

the first cycle of selection. Kelly (7) found recurrent selection

to be effective in the development of erect, indeterminate pinto

beans. The moderate to low narrow sense heritability values for

" seed yield indicate that individual plant selection for seed yield

in early generations would not be effective (Table 2). The

magnitude of the narrow sense heritabil cities are in general

agreement with previous research (4,8). These results suggest that

it would be more effective for breeders to select simply or highly

heritable traits such as -seed type, growth habit, relative

maturity, and resistance- to specific diseases in the early

generations. Selection for seed yield would be more effective in

replicated trials in advanced generations.

Number of pods per plant of the F. lines was significantly

less than their indeterminate parents for four of the six

populations at Constanza, the low yield environment (Table 1).







Narrow sense heritability estimates for number of pods per plant

were similar in magnitude to the narrow sense heritabilities for

seed yield (Table 2). As was Ifound in previous research (3,4),

number of pods per plant was highly correlated with seed yield at

both locations (Table 3).

Hu ndred seed weight of the F_ lines was greater at Constanza

than at Juana Diaz (Table 4). This is possibly due to a lack of

rainfall during flowering and pod set which reduced pod set per

plant. The plants, however were able to compensate for more

favorable environmental conditions during the latter part of the

growing season by producing larger seeds (1). Hundred seed weight

of the indeterminate F, lines was significantly less than their

determinate parents. The results again point to the need to

evaluate large populations in order to identify indeterminate F3

lines with seed sizes that are similar to their determinate

parents. Kelly (7) has noted in his effort_ to develop erect,

indeterminate pinto beans that desirable plant types are often

associated with small seed size. Narrow sense heritabilities for

100 seed weight tended to be low to intermediate in magnitude at

both locations (Table 5). Since it is such a simple trait to

measure, selection for greater seed size could begin in the early

generations. F'henotypic correlations between seed size and seed

yield were generally positive or non-significant (Table 3). The

lack of negative phenotypic correlations between seed yield and

100 seed weight indicates that the simultaneous selection for

greater seed yield and seed size might be possible.






Number of seed per pod of the ::, lines tended to be intermediate

between their determinate and indeterminate parents (Table 4).

Little difference was observed between locations for number of

se-eds per pod. Narrow sense heri ability estimates for number of

seeds per pod were low to intermediate (Table 5). Only two of the

six populations had significant phenotypic correlations between

sec:d yield and number of seed per pod at Juana Diaz (Table 3). In

Cor is tanrza, however, five of the six populations had significant

rcorrelations between number of seed per pod and seed yield. A

grea ciL.e number of seed per pod might have provided an opportunity

for plants in Constanza to partially compensate for a reduced

number of pods per plant (1).

Spearman rank correlations between the Fortuna and Juana Diaz

locations for seed yield and its components varied among

populations (Table 6). These results indicate that a large number

of. different populations should be developed in order to identify

populations which produce lines that perform well in contrasting

environments. Nienhaus and Singh (8) identified bean populations

which had positive general combining ability for yield in more

than one environment. These results also illustrate the

desirability of multi-location testing of advanced lines in

environments which are representative of the bean growing regions

of _the Dominican Republic. Hundred seed weight was the only

characteristic with significant rank correlations- for all

populations. This indicates that selection for seed size at one

location would be effective for a wide range of environmental

condi ti ons.





REFERENCES


1. Adams, M.W. 1967. Basis of yield component compensation with
special reference to the field bean (Phaseolus vulgaris L.).
Crop Sci. 7:505-510.

2. Beaver, J.S., C.V. Paniagua, D.P. Coyne, and G.F. Freytag. 1985.
Yield stability of dry bean genotypes in the Dominican Republic.
Crop Sci. 25:923-926.

3. Camacho, L.H., C. Cardona, and S.H. Orozco. 1966. Genotypic and
phenotypic correlation of component of yield in kidney beans.
Bean Improvement Cooperative 7:8-9.

4. Coyne, D.PF. 1968. Correlation, heritability, and selection of
yield components in field bean. (haseolus'vulgaris L.). Crop Sci.
10:246-248.

5. Gepts, F. and F.A. Bliss. 1985. F hybrid weakness in the
common bean. Journal of Heredity 76:447-450.

6. Hallauer, A.R. and J.B. Miranda.1981. Quantitative genetics in
maize breeding. Iowa State Univ. Press.Ames, Iowa.

7. Kelly, J.D. and M.W. Adams. 1986. Utilization of phenotypic
recurrent selection in bean breeding. Bean Improvement
Cooperative 29:11-12.

8. Nienhaus, J. and S.P. Singh. 1986. Combining ability analysis
and relationships -among yield, yield components, and
architectural traits in dry bean. Crop Sci. 26:21-27.

9. Quinones, F.A. 1965. Correlation of characters in dry beans.
Proc. Amer. Soc. Hort Sci. 86:368-372.

10.Singh, S.P. and J.A. Guiterrez. 1984. Geographical distribution
of the DL1 and DL, genes causing hybrid dwarfism in Fhaselous
vulgaris L., and their association with seed size, and their
significance to breeding. Euphytica 33:337-345.






lable I. IlLan seed yield and number of pods per plant of parents and
indcAtermi nate F- populations of si:: bean populations grown at
Constanza, Domih'iican FRepublic arid Juana Diaz, FPuerto Rico.

Number of pods
N~imber of po~ds


Seed yield


per- p3 ant


Fopulati on


Geereration Constanz a Juana Diaz


Constanza Juana Diaz


-g)/pl ant-

Pomp. checa X F / 9 16 8.0 17.1
H-376 F, 18 23 2().9 27.7

F, 12t. 17 1 1.94 19.7*.

Jose Ieta X F 10 16 7.2 12.9
H-376 p'. 19 21 22.3 24.6

F, 12: 17*: 11.9* 18. 0*

La Vega X F" 9 17 7.5 16.9
Pomp. checa F:, 16 19 14.8 22.0


10 *


La Vega X
Jose Beta



8241-168A X
PA I 92



PAI 92.X
Bori nquen


16


18
18

14.*

20(
18

20


1 0. 2 *

6.1
14.9

12.3%*

5.8
-10.8

10. 4

4.7
11.4

11.-0


19.6

11.2
22.1

20. 6

14.3
19.3

17.4

14.7.
19.5

20.7


1/ F'P = determinate parent and P, = indeterminate parent
1
3 Significantly different from tHe indeterminate parent at the 0.05
probability level.







Table 2. Narrow sense heritabilities for seed yield and number
of pods per plant. Heritabil.ities were estimated using parent-
ofCspring regressions of indeterminate F. and F. plants
of si: bean populations grown at Constan a, Dominican Republic
and Juana Di a Puerto Rico.


Seed yield Number of pods per plant

F'opul] action Constanza Juana Diaz Constanza Juana Di a

-y/plant-


F'onip. c-h -ca > 30 O C. 57 0. 44


IJose BcDta X 0.37 0.60 o 0.63 -0. 13


La Vega X 0.39 .0.34. 0.33 0.51
F'omp. checa

La Vega X ( 0.18 0.22 O0 0.47
Jose Beta

8241-168A X 0.59 0 C. 19 0.28
PAI 92

PAI 92 X 0 0 0 C. 19
Pori nquen






able 3. Fhenotypic correl-ations between number of pods per plant,
hundred seed weight, number of seed per pod and seed yield.
Correlations were estimated using F, plants of six bean pop-
ulations grown at Constanza, Dominican Republic and Juana Diaz
Puerto Rico.

Number of pods Hundred seed Number of seed
per plant weight per pod

Population Const. J. Diaz Const. J. Diaz Const. J. Diaz



F. checa X 0.82 1/ 0.'77*1 0.07 0.23 0.28 0.46 4
H-376

Jose Beta X 0.69*. 0.81*3 o. 14 0. 11 0O17 0.23
H-376

La Vega X 0.82** 0.85 t 0.29 -0.05 0.47** 19
Pomp. checa

La Vega X 0.63.: 0.79* 4 0.50t*C -0.01 0.49t* 0.01
Jose Beta

82'11-168A X O. 0** 0.85** 0.24 0.53t* 0.50*:. 0.41**
PAI 92

PFA1l 92 X 0.81 0.86*. 0.39* 0.11 0.42** 0.07
Borinquen



1/ *,**:-Significant at the 0.05 and 0.01 probability levels,
respectively






able 4. Mean hundred seed weight and number of seed per pod of parents
and indetermi nate F. populations of six bean populations grown at
Cohstanza, Dominican Republic and Juana Diaz, Puerto Rico.

Hundred seed Number of seed
weight per pod

F'opulation Generation Constan::a Juana Diaz Constanza Juana Diaz

-9-

Pomp. checa X P 1/ 5. 9 29. 2 3. 1 3. 2
H-376 PF 24.3 19.6 3.8 4.3

F. 26. It 22.2#t 4.0 3.9t

Jose Beta X F' 48.4 41.0 2.9 3.1
H-376 P7, 20.9 19.8 4.6 4.3

F3 29.7# 26.5# 3.6* 3.7

La Vega X FP 35.4 30.0 3.2 3.3
, Fomp. checa F', 23.2 20.2 4.7 4.2

F. 28.5# 24.5# 3.5* 3.4*

La Vega X P 49.9 45.5 2.6 3.1
Jose Beta 'P 22.0 20.1 4.1 4.4

F- 27.9# 25.5# 4.0 3.9*

82-41-168A X FP 37.1 32.4 3.4 3.8
PAI 92 PF2 23.7 21.7 4.1 4.3

F3 27.0# 24.6# 3.5* 3.44

PAI 92 X P .29.2 29.7 3.2 4.2
Borinquen P'- 24.1 22.3 4.1 4.6

F3 25.9# 23. 7# 3.8 4.1*


I/ PF = determinate parent and PF = indeterminate parent
# Significantly different from tNe determinate parent at the 0.05
probability- level.
* Significantly different from the indeterminate parent at the 0.05
probability level.









Table 5. Narrow sense heritabilities for hundred seed weight and
and number of seed per pod. Heritabilities were estimated using
parent-offspring regressions of indeterminate F. and F,
plants of six bean populations grown at Constanza, Dominican
Republic and Juana Diaz,. Puerto Rico.


Hundred seed weight Number of seed per pod
--- -- --- -- --- -- -- --~--- -- ------- --'-- --------
Populati on Constanz Juana Diaz Constanza Juana Di az

-9-


FPonmp. ceca X 0.25 0.22 0. 11 0.40
0.4 0
H-376

Jlose Beta X 0.37 0.45 0.23 0.24
H-376

La Vega X 0. 33 23 0.15 0.19
Pomp. checa

La Vega X 0.51 0.44 0.25 0.30
Jose Beta

8241-168A X 0.40 0.40 0. 19 0. 10
PFA I 92

PAI 92 X 0. 33 0.20 0 0.64
or i nquen









Table 6. Spearman ranl correlations between Constanza, Dominican
Republic and Juana Diaz Puerto Rico for F_ family means for
seed yield, number of pods per plant, hundred seed weight, and
number of seed per pod.
------------------------------------------------------------------------------

Seed Number of pods Hundred seed .Number of
Population yield per plant weight seed per plant
--------------------------------------------------------------------------


Pomp. checa X 03 0.17 0.54* U. 14
H--376

Jose IOic a X 0..32* 42** 0.53 :* 0.60* :
IH- 176

La Vega X 0.01 0.38 0. C. 74*t 0.20
Pomp. checa

La Vega X 0., 5 0.706. 0. 68** 0.12
Jose Beta

8241-168A X 0.29* 0. 10 .37*t 0.33*
PAl 92

FPA 92 X 0.31* 0.07 0.37** 0.32**
-Borinquen


------------------------------------------------- 7 ------ 7------------

1/ *,** Significant at the 0.05 and 0.01 probability levels,
respectively.






EARLY GENERATION SELECTION FOR HIGH YIELD IN BEANS USING PHYSIOLOGICAL
COMPONENTS OF YIELD AS SELECTION CRITERIA

P.N. MASAYA *, J.W. WHITE *, D.H. WALLACE --:' AND R. RODRIGUEZ .



1. INTRODUCTION


Superior yield is an important, if not the ultimate goal of any
plant breeder. The several breeding methods are meant to identify and
perpetuate those genotypes with the potential for superior yield. Yield
being the result of all genes in the plant, is difficult to see as a -
trait at the time of individual or mass selection.

When making individual selections the breeder must keep in mind
that yield is produced by a community of plants growing together on a
given area of land in a given period of time. Such a plant community
must have the capability for the efficient use of the sunlight radiation,
C02 water, and soil nutrients during a growth cycle that is fixed by a
agricultural or climatological characteristics. Donald (3) has emphasized
the differences in viewing the yield per plant and the yield per unit of
land. Wallace (12), and Wallace et al (14) pointed the features required
in a cultivar for accomplishing the efficient use of time and environmental
resources for seed yield. The breeder, then, should visualize the plant
being selected as growing in a homogeneous or heterogeneous plant popular
tion, as monoculture or as a mixture of crops, but in any case, being
part of a stand.

The environment modulates plant growth, by its factors: water avai-
lability, soil fertility, temperature, photoperiod and light quality. The
bean plant responds to the environment by developing varying numbers of
branches, nodes on branches, roots and rootlets, and later, of pods, de
pending on the intensity or quality of environment factors. For example,
when the temperature is warmer, in the range from 190C through 290C(mean
temperature), the internodes are longer, and leaves are more numerous (7)
(6). Long day, promote bigger leaves, more numerous nodes and a longer
period of growth, in comparison to short days, specially in photoperiod
sensitive cultivars (5) (6) (11) (13).



* Bean Breeders. Institute de Ciencia y Tecnologla Agrlcolas -ICTA-

** Bean physiologist. Bean Program. Centro Internacional de Agricult.u
ra Tropical -CIAT- Call, Colombia.

-* Profesor. Department of plant Breeding and Biometry. Cornell Univ.






The neighboring plants have a strong effect on the growth of the
bean plant. This is specially intense in an F2 population where each
plant has a different genome. Plants with a more aggressive growth
reduce the growth and the seed yield of adjacent, less aggressive plants.

Since plant phenotypes are affected by the environment there is the
need for a testing of progenies or lines in early or advanced generations.
In fact, all breeding methods include some means of testing the result of
selection. The breeder uses then her or his experience and knowledge of
the crop and a proper methodology for reducing the amount of lines to be
:ested, since the line testing, is the most expensive part of the bree--
ding scheme.

It is considered that selection in early generations for yielding
ability is non productive because of low heritability of yield charac-
ters (14) (10) (8). Is is futile to attempt identifying by visual ins-
pection the plants which produce progenies with superior yield. The bree
der can discardthe plants with obvious defects or plants with poor ar-
chitecture. On the other hand, an empirical selection seems unavoidable
(4), followed by progenie or line testing, of yield.

In many bean breeding programs, a multiple objective scheme is ne-
cessary as when breeding for resistance to several diseases, as in CIAT
bean program. In such situations, it is highly desirable to reduce by
some early selection the number of lines to carry through advanced gene
rations and through on farm trials. Recurrent selection and crossing is
becoming more used in bean breeding. An early identification of superior
crosses and lines for new combinations is essential for efficient recurrent
selection. (10).

It has been advocated before the need for an integrative selection
that should be able to select those plants that have the more complete
combination of genes for yield (13, 14). Since all genes in the plant
affect adversely or favorably the seed yield, it is difficult to identi
fy or predict which combination of genes will give the highest yield,
and which plant has the very combination of genes for superior yield.
Because of that reasoning it is considered more practical to measure the
outputs of the yield process more closely related to the seed yield (12).
They are: a) the total plant weight, which measures the ability of the
plant for accumulating dry matter; b) the efficiency in partitioning,
that is, the ability of the plant for diverting the accumulated dry ma-
tter toward the seeds. Such efficiency is measured by the harvest index,
indicated by Wallace for bean breeding (12). The harvest index is defi
ned as the ratio of seed weight divided by the total plant weight.
The ideal, high yielding genotype, coupled to the ideal crop management,
should combine the largest total weight and a large value of harvest in
dex, that is, the largest proportion of the total plant weight put into
seeds.
The use of both, total plant weight and harvest index as selection
criteria requires facilities for storing, drying and weighing whole plants
(excluding leaves and petioles) besides the weighing of seeds. In beans,




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