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 Front Cover
 Title Page
 Copyright
 Table of Contents
 Abstract
 Acknowledgement
 List of Tables
 Figures
 Introduction
 The valley of Cuzalapa and the...
 Methodology
 Cultivars and seed exchange
 Phenotypic diversity of variet...
 Discussion
 Implications for In Situ conse...
 Reference
 New papers from the Natural Resources...
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Group Title: Paper - Natural Resources Group - 96-03
Title: Genetic diversity and maize seed management in a traditional Mexican community
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Permanent Link: http://ufdc.ufl.edu/UF00077520/00001
 Material Information
Title: Genetic diversity and maize seed management in a traditional Mexican community implications for in situ conservation of maize
Series Title: Paper Natural Resources Group
Physical Description: v, 21 p. : ill. ; 28 cm.
Language: English
Creator: Louette, Dominique
Smale, Melinda
Publisher: CIMMYT
Place of Publication: Mexico D.F
Publication Date: 1996
 Subjects
Subject: Corn -- Germplasm resources -- Mexico   ( lcsh )
Corn -- Seeds -- Mexico   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 20-21).
Statement of Responsibility: Dominique Louette and Melinda Smale.
 Record Information
Bibliographic ID: UF00077520
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 35769400
issn - 1405-2830 ;

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Table of Contents
    Front Cover
        Front cover
    Title Page
        Page i
    Copyright
        Page ii
    Table of Contents
        Page iii
    Abstract
        Page iv
    Acknowledgement
        Page iv
    List of Tables
        Page v
    Figures
        Page v
    Introduction
        Page 1
    The valley of Cuzalapa and the Sierra de Manantlan biosphere reserve (SMBR)
        Page 2
        Page 3
    Methodology
        Page 4
        Page 5
    Cultivars and seed exchange
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
    Phenotypic diversity of varieties
        Page 13
        Page 14
        Page 15
    Discussion
        Page 16
        Page 17
    Implications for In Situ conservation
        Page 18
        Page 19
    Reference
        Page 20
        Page 21
    New papers from the Natural Resources Group
        Page 22
    Back Cover
        Back cover
Full Text



II
CIMMYT
Sustainable Maize
and Wheat Systems
for the Poor






Genetic Diversity and Maize

Seed Management in a

Traditional Mexican Community:

Implications for In Situ

Conservation of Maize
Dominique Louette and Melinda Smale






Natural Resources Group
Paper 96-03









I


CIMMYT


Genetic Diversity and Maize Seed

Management in a

Traditional Mexican Community:

Implications for In Situ

Conservation of Maize

Dominique Louette and Melinda Smale *




Natural Resources Group
Paper 96-03



Dominique Louette is Doctor of Agronomy and Researcher at the Instituto Manantlin de Ecologia y Conservaci6n de
la Biodiversidad (IMECBIO) of the University of Guadalajara in Mexico. The research on which this article is based
was conducted while she was a graduate student at the Ecole Nationale Superieure d'Agronomie of Montpellier
(ENSAM) in France and was funded by a scholarship of the Mexican Secretaria de Relaciones Exteriores and by
Pioneer G6entique S.A.R.L. (France). Dr. Louette is currently conducting related post-doctoral research funded by the
International Maize and Wheat Improvement Center (CIMMYT) in Mexico. Melinda Smale is an Economist for
CIMMYT and assisted with the preparation of this manuscript.



























CIMMYT is an internationally funded, nonprofit scientific research and training organization.
Headquartered in Mexico, the Center is engaged in a research program for maize, wheat, and triticale,
with emphasis on improving the productivity of agricultural resources in developing countries. It is one
of several nonprofit international agricultural research and training centers supported by the
Consultative Group on International Agricultural Research (CGIAR), which is sponsored by the Food
and Agriculture Organization (FAO) of the United Nations, the International Bank for Reconstruction
and Development (World Bank), and the United Nations Development Programme (UNDP). The
CGIAR consists of some 40 donor countries, international and regional organizations, and private
foundations.

CIMMYT receives core support through the CGIAR from a number of sources, including the
international aid agencies of Australia, Austria, Belgium, Brazil, Canada, China, Denmark, Finland,
France, India, Germany, Italy, Japan, Mexico, the Netherlands, Norway, the Philippines, Spain,
Switzerland, the United Kingdom, and the USA, and from the European Union, Ford Foundation, Inter-
American Development Bank, OPEC Fund for International Development, UNDP, and World Bank.
CIMMYT also receives non-CGIAR extra-core support from the International Development Research
Centre (IDRC) of Canada, the Rockefeller Foundation, and many of the core donors listed above.

Additional information on CIMMYT activities is available on the World Wide Web at:
http:/ /www.cimmyt.mx or http:/ /www.cgiar.org

Responsibility for this publication rests solely with CIMMYT.

Printed in Mexico.

Correct citation: Louette, D., and M. Smale. 1996. Genetic Diversity and Maize Seed Management in a
Traditional Mexican Community: Implications for In Situ Conservation of Maize. NRG Paper 96-03. Mexico,
D.F.: CIMMYT.

Additional information on CIMMYT activities is available on the World Wide Web at:
http:/ /www.cimmyt.mx or http:/ /www.cgiar.org

ISSN: 1405-2830
AGROVOC descriptors: Zea mays; varieties; germplasm; genetic resources; agronomic characters;
innovation adoption; crop management; Mexico
AGRIS category codes: E14
Dewey decimal classification: 338.14











Contents

Page

iv Abstract
iv Acknowledgments
v Tables
v Figures

1 Introduction

2 The Valley of Cuzalapa and the Sierra de Manantlin Biosphere Reserve (SMBR)

4 Methods
4 "Seed lot" and "variety" defined
5 Documenting the exchange of seed and varieties
5 Measuring morphological diversity

6 Cultivars and Seed Exchange
6 Cultivars
8 Seed exchange
10 The pattern of varietal diffusion
11 Farmer type
12 Factors explaining seed exchange

13 Phenotypic Diversity of Varieties
13 Phenotypic characteristics and varietal identification
14 Phenotypic variation between varieties

16 Discussion

18 Implications for In Situ Conservation


20 References










Abstract


Results from a study of maize varieties and seed sources in a traditional community in Mexico
raise questions about the relevance of models for in situ conservation of crop genetic resources that
are based on geographical isolation of the community, as well as the relationship between genetic
erosion and the introduction of varieties. The morphophenological diversity of local materials is
shown to be enhanced by introductions of both improved cultivars and landraces from farmers in
other communities. Evidence on seed sources and selection practices also reveals that the
geographical point of reference for defining a "local" landrace is larger than the community itself.
Farmers often obtain seed for their landraces from other farmers in and outside the community,
rather than select seed exclusively from their own harvests. A farmer will classify seed obtained
from another community as that of a local landrace if it resembles one of his own, according to the
phenotypic characteristics that he uses to distinguish varieties. A more appropriate model for
conserving maize diversity in this community would be to permit a certain level of introductions
while assuring that the extent of cultivation of local varieties is sufficient to maintain a desirable
level of polymorphism. The design of such an in situ system would clearly be much more complex
than the simple model based on geographical isolation would suggest.


Acknowledgments


The authors acknowledge the theoretical and conceptual contributions of A. Charrier (ENSAM)
and J. Berthaud (ORSTOM) during the implementation and analysis of the research. The authors
also acknowledge the review of Robert Bird.










Abstract


Results from a study of maize varieties and seed sources in a traditional community in Mexico
raise questions about the relevance of models for in situ conservation of crop genetic resources that
are based on geographical isolation of the community, as well as the relationship between genetic
erosion and the introduction of varieties. The morphophenological diversity of local materials is
shown to be enhanced by introductions of both improved cultivars and landraces from farmers in
other communities. Evidence on seed sources and selection practices also reveals that the
geographical point of reference for defining a "local" landrace is larger than the community itself.
Farmers often obtain seed for their landraces from other farmers in and outside the community,
rather than select seed exclusively from their own harvests. A farmer will classify seed obtained
from another community as that of a local landrace if it resembles one of his own, according to the
phenotypic characteristics that he uses to distinguish varieties. A more appropriate model for
conserving maize diversity in this community would be to permit a certain level of introductions
while assuring that the extent of cultivation of local varieties is sufficient to maintain a desirable
level of polymorphism. The design of such an in situ system would clearly be much more complex
than the simple model based on geographical isolation would suggest.


Acknowledgments


The authors acknowledge the theoretical and conceptual contributions of A. Charrier (ENSAM)
and J. Berthaud (ORSTOM) during the implementation and analysis of the research. The authors
also acknowledge the review of Robert Bird.










Tables

Page

4 Table 1. General characteristics of maize cultivation in Cuzalapa, Mexico

6 Table 2. Vegetative, tassel, and ear descriptors measured in the maize genetic diversity
study, Cuzalapa, Mexico

7 Table 3. Relative importance of different maize varieties cultivated in Cuzalapa, Mexico

9 Table 4. Origin of seed lots used in Cuzalapa, Mexico (by variety)

15 Table 5. Principal characteristics of the 14 varieties studied in Cuzalapa, Mexico

Figures

2 Figure 1. Location and zoning of the Sierra de Manantlin Biosphere Reserve and the
Cuzalapa indigenous community limits within the reserve

10 Figure 2. Origin of maize seed planted in Cuzalapa, Mexico, by origin of variety

11 Figure 3. Classification of the 39 farmers surveyed in Cuzalapa, Mexico, by the origin of their
maize seed

14 Figure 4. Hierarchical Cluster Analysis of seed lots of five varieties by phenotypic
characteristics

14 Figure 5. Phenotypic diversity of maize varieties planted in Cuzalapa, Mexico: Factorial
Discriminant Analysis of vegetative, tassel, and ear characteristics, axes 1 and 2










Tables

Page

4 Table 1. General characteristics of maize cultivation in Cuzalapa, Mexico

6 Table 2. Vegetative, tassel, and ear descriptors measured in the maize genetic diversity
study, Cuzalapa, Mexico

7 Table 3. Relative importance of different maize varieties cultivated in Cuzalapa, Mexico

9 Table 4. Origin of seed lots used in Cuzalapa, Mexico (by variety)

15 Table 5. Principal characteristics of the 14 varieties studied in Cuzalapa, Mexico

Figures

2 Figure 1. Location and zoning of the Sierra de Manantlin Biosphere Reserve and the
Cuzalapa indigenous community limits within the reserve

10 Figure 2. Origin of maize seed planted in Cuzalapa, Mexico, by origin of variety

11 Figure 3. Classification of the 39 farmers surveyed in Cuzalapa, Mexico, by the origin of their
maize seed

14 Figure 4. Hierarchical Cluster Analysis of seed lots of five varieties by phenotypic
characteristics

14 Figure 5. Phenotypic diversity of maize varieties planted in Cuzalapa, Mexico: Factorial
Discriminant Analysis of vegetative, tassel, and ear characteristics, axes 1 and 2










Genetic Diversity and Maize Seed Management in
a Traditional Mexican Community:
Implications for In Situ Conservation of Maize


Dominique Louette and Melinda Smale


Introduction

A major preoccupation of those concerned
today with the conservation of plant genetic
resources is that in many regions of the world,
farmers have economic incentives to replace the
varieties that evolve within their own
agrosystem with improved, introduced
varieties. To forestall the disappearance of
locally evolved varieties in farmers' fields, some
have proposed in situ conservation as a
complementary strategy to ex situ conservation
of genetic resources in gene banks. As originally
defined, in situ conservation means preserving,
in their original agrosystem, varieties cultivated
by farmers using their own selection methods
and criteria (Bommer 1991, FAO 1989, Keystone
Center 1991).

One model of in situ conservation, described by
Iltis (1974), is that of a reserve in which neither
changes in cultural practices nor the
introduction of foreign genetic material are
permitted. In essence, in situ conditions would
reproduce the conditions found in ex situ
conservation, by fixing genetic structures and
growing environment. The reserve model has
been criticized widely on the grounds that it is
not feasible for socioeconomic reasons. The
model has also raised numerous questions
about how policies aimed at fostering economic
development relate to those designed to
conserve plant genetic resources and whether
conservation can coexist with the integration of
communities into commercial markets (Cohen
et al. 1991, Cooper et al. 1992, Montecinos and


Altieri 1991). More specifically, should the
objective of in situ conservation be to fix the
genetic diversity of the landraces cultivated in
traditional farming systems? Is this view of in
situ conservation consistent with the way
traditional farming systems function? Does it
respect the mechanisms that explain the
diversity found in farmers' fields for an open-
pollinated, cultivated plant such as maize ?

Answering these questions requires two
fundamental pieces of information which have
been largely missing from the debate over
conservation strategies. The first is a clear
definition of conservation objectives in terms
that are meaningful for scientists, policy
makers, and those who inform policy makers.
The second is specific knowledge about the
origin and dynamics of the diversity that can
be observed on traditional farms. To be able to
define precisely the objectives, limits, and
means for implementing in situ conservation, it
is necessary to obtain a better understanding of
the structure of polymorphism within farmers'
varieties, how it evolves with farmers'
practices, and the methods and mechanisms for
managing this source of diversity (FAO 1989,
Brush 1992). Without this information, neither
a constructive debate nor an adequate
methodology for in situ conservation can be
established.

The larger study from which the arguments
and data presented here are drawn (Louette
1994) examines the structure of genetic
diversity in maize and analyzes the effect of










farmers' seed management strategies on this
structure in Cuzalapa, an indigenous
community of western Mexico. Two specific
questions are examined in this paper. The first
is to what extent the genetic diversity that can
be observed in the maize varieties of Cuzalapa
results from the management of materials of
strictly local origin. The second question is to
what extent the introduction of foreign material
is associated with a loss of genetic diversity.
Data on sources of seed illustrate the important
role played by seed acquired from other
farmers in and outside the region relative to
seed that local farmers obtain from their own
harvests. Analyses of phenotypic and
phenological characteristics, combined with
data on origin of seeds, demonstrate the effect
of introduced varieties on the diversity of maize
cultivated in the Cuzalapa community.

The next section of this paper summarizes
essential features of the farming system in
Cuzalapa. Subsequent sections include a
description of the methods used in the study,
results of the analysis of data on genetic
diversity and seed flows, a discussion of results,
and the implications of our findings for the
questions posed above.

The Valley of Cuzalapa and the
Sierra de Manantlin Biosphere
Reserve (SMBR)

The indigenous community of Cuzalapa is
located in a valley in the southern section of the
buffer zone of the Sierra de Manantlin
Biosphere Reserve (SMBR), in the municipality
of Cuautitlin on the Pacific Coast of Mexico
(Figure 1). The Biosphere Reserve's interest in
conserving in situ the genetic resources of the
genus Zea (Jardel 1992) is explained by its


location on the Pacific Coast of Mexico, which
may be one of the zones where maize
originated (Benz and Iltis 1992). In the reserve
and nearby, various species of Teosinte (a wild
relative of maize) are found,1 growing
alongside primitive races of maize such as
Tabloncillo and Reventador (Wellhausen 1951,
Benz 1988 and forthcoming, Benz et al. 1990).

The regional importance of Cuzalapa has
declined since the beginning of the colonial
period in the 16th century, when it became the
principal community of the Provincia de
Amula de Occidente. The valley of Cuzalapa
has approximately the same number of
inhabitants today (1,500) as it did in 1540
(Laitner and Benz 1994). Although it is one of
the largest communities of the Biosphere
Reserve, Cuzalapa is also located in one of the
most marginalized municipalities of the region,
based on quality of housing and level of
education. The population is distributed among
the main village of Cuzalapa and 23 other
localities. At the time of this study (1989-91),


Figure 1. Location and zoning of the Sierra
de ManantlIn Biosphere Reserve and the
Cuzalapa indigenous community limits
within the reserve.


1 Zea mays spp. parviglumis Iltis, Doebley; Zea diploperennis Iltis, Doebley, Guzman; and Zea perennis (Hitchc.) Reeves,
Mangelsd.










these localities were all relatively isolated from
major roads and urban areas.

Because of its largely indigenous population,
the valley of Cuzalapa was officially
recognized as a comunidad indfgena (indigenous
community) under the Agrarian Reform of
1950. Theoretically, land in the valley is held in
common and political structures are based on
traditional institutions such as the consejo de
ancianos (council of elders). The community
nevertheless functions like an ejido2 in the sense
that land is partitioned among the comuneros
and its use is governed by an elected assembly.
A great proportion of the inhabitants are in fact
mestizos (of combined European and
indigenous ancestry).

The Cuzalapa watershed covers nearly 24,000
ha (most of which lies within the boundary of
the Biosphere Reserve) of mountainous land of
extremely irregular topography, ranging from
an elevation of 550 m to 2,660 m. The
agricultural zone is located at an elevation of
600 m and has a hot subhumid climate, with a
mean annual temperature of 220C and mean
annual precipitation of 1,500 mm, concentrated
from June to October (Martinez et al. 1991).
Fields used for cropping are generally located
near rivers on alluvial soils3 of moderate
fertility (Martinez and Sandoval 1993).

Maize (Zea mays spp. mays) is the dominant
crop in the valley, where it is planted during
the rainy season from June to November and
also under irrigation in the dry season
extending from December to May. Farmers
surveyed in Cuzalapa obtained mean maize
yields of 2.8 t/ha unshelledd) during the rainy
season and 2.1 t/ha unshelledd) in the dry


season (under irrigation). Pumpkin is the
primary associated crop for more than half of
the survey farmers during the rainy season. In
the dry season, the majority of survey farmers
intercrop beans with maize. Irrigation and
intercropping are not new practices in the area:
they were reported to be a feature of
agriculture in Cuzalapa in pre-colonial times
(Laitner and Benz 1994). Until commercial
opportunities disappeared in the 1970s, flooded
rice was also cultivated during the rainy
season. Extensive cattle raising is now
emerging as a commercial activity.

Each year, about 1,000 ha may be sown in
Cuzalapa; of this area, 600 ha are irrigated
(Martinez and Sandoval 1993). The average
area planted to maize per farmer is about 2 ha
in the rainy season and more than 2 ha in the
dry season (Table 1). The dry season is the most
important cropping season because it involves
fewer climatic risks than the rainy season; for
example, violent winds in the rainy season can
cause major crop losses due to lodging. During
the dry season, irrigated maize, beans
(Phaseolus vulgaris var. bayo and bayo
berrendo), and small quantities of green tomato
(tomatillo, or Physalis philadelphicum, which
grows spontaneously) can be harvested on the
same field.

Cultural practices have evolved in Cuzalapa
but continue to be relatively traditional when
compared to those found outside the Sierra de
Manantlin (Table 1). Farmers generally till the
soil with horse-drawn plows in the rainy
season. Tractors are used more frequently
during the dry season because the economic
returns to maize production in that season are
greater and more reliable, and the irrigable


2 Communally held agricultural land.
3 These soils are Fluventic Hapludolls and Tipic Udifluvents, according to the U.S. Department of Agriculture Soil
Conservation Service classification.











soils contain fewer rocks. Weeds are usually
controlled by horse-drawn cultivator before
sowing and one month after sowing. Sowing,
fertilization, and harvesting are always manual
operations. The irrigation technique, which is a
very old one, is based on gravity. Farmers
construct canals from the river to the field
before planting and inside the field during
cultivation. Water is conducted through the
field by closing or opening furrows or
secondary canals.

Beans are produced exclusively for home
consumption. Part of the annual maize crop
and almost all of the tomatillo crop of Cuzalapa
are sold outside the valley, yet the Cuzalapa
community is poorly integrated into
commercial markets. Based on its farming and
socioeconomic characteristics, Cuzalapa can be
considered representative of many indigenous,
poor, and isolated rural areas in Mexico.


Cuzalapa is one of the many traditional
communities which are being drawn slowly
into commercial marketing systems while
maintaining features of indigenous society.

Methods

"Seed lot" and "variety" defined
A "seed lot" consists of all kernels of a specific
type of maize selected by a farmer and sown
during a cropping season to reproduce that
particular maize type. The definition of
"variety" or "cultivar" used in this study was
also developed from farmers' own practices
and concepts. A "variety" is defined as all seed
lots held by farmers that bear the same name
and are considered by them to form a
homogeneous set. A seed lot therefore refers to
a physical unit of kernels associated with the
farmer who sows it, whereas a variety is
associated with a name.


Table 1. General characteristics of maize cultivation in Cuzalapa, Mexico (mean data;
maximum and minimum in parentheses)


Rainy season, 1989
(Surveyed fields = 21)


Cultural practices
Tractor use (% farmers) 27
Chemical fertilizer use (% farmers) 86
Quantity of fertilizer applied (kg N/P/K per ha) 86-3-0 (0-226/0-30/0-7)
Insecticide use (% farmers) 43
Herbicide use (% farmers) 14


Maize
Area sown per farmer (ha)
Number of maize varieties sown
per farmer and per cycle
Seed germination (%)
Plant density (1000 plants/ha)
Number of ears produced per plant
Maize yield (kg ears/ha)

Associated crop
Percentage of farmers planting
Mean density (1000 plants/ha)


Dry season, 1990
(Surveyed fields = 19)


74
89
78-0.5-0
16
0


1.9 (0.2-7.9)


2.6
80
45.0
0.65
2,830


(0-129/0-8/0-8)


2.6 (0.4-6.8)


(1-6)
(66-93)
(32.5-66.8)
(0.27-0.91)
(1,180-4,510)


2.4
65
34.1
0.68
2,120


Pumpkin
57
1.0 (0.4-1.6)


(1-7)
(47-73)
(20.0-52.3)
(0.46-0.93)
(1,290-3,950)


Bean
84
179 (42-263)


Source : Louette (1994).










A maize variety is defined as "local" when seed
from that variety has been planted in the region
for at least one farmer generation (that is, for
more then 30 years or if a farmer maintains that
"my father used to sow it"). This definition
implies that a local variety has been cultivated
continuously among survey farmers in
Cuzalapa for many years. By contrast, a
"foreign" variety is characterized either by the
recent introduction of its seed lots or by
episodic sowing in the valley. Landraces are
farmers' varieties which have not been
improved by a formal breeding program.
Foreign varieties may include landraces from
other regions and commercial improved
varieties recently or repeatedly reproduced by
farmers using traditional methods.

Documenting the exchange of
seed and varieties
To document which maize varieties are
cultivated and to record the exchange of seeds
and varieties in the community and between
the valley of Cuzalapa and other regions, 39
farmers were surveyed during six cropping
seasons covering three calendar years (the 1989,
1990, and 1991 rainy and dry seasons). For each
farmer and cropping season, data were
collected on varieties cultivated and seed
source. Cultivars included those grown on the
farmer's own fields, those grown on rented
fields, and those grown on fields in association
with other farmers. Each variety was registered
with the name given by the farmer. When seed
was introduced from another region and bore
the same name as a local variety, farmers were
consulted about whether or not the seed should
be differentiated from the local material. When
the seed shared the same name as a local
variety but was not considered by the farmer
growing it to be the local variety, a second label
was noted in brackets for example, "Negro
[Foreign]."


The seed source was classified in three ways:
(1) as own seed (seed selected by the farmer
from his own harvest); (2) as seed acquired in
Cuzalapa (seed obtained in the valley of
Cuzalapa from another farmer); and (3) as an
introduction (seed acquired outside of the
Cuzalapa watershed). The origin of a seed lot is
defined independently of the origin of the
previous generation of seed. A seed lot is
considered "own seed" if the ears from which
the kernels were selected were harvested by
the farmer in his field in Cuzalapa, even
though the seed that produced those ears (i.e.,
the previous generation of seed) may have
originated in another region. The data
therefore represent well the extent of seed
exchange, but they understate the importance
in Cuzalapa of seed with foreign origin.

Measuring morphological diversity
The structure of phenotypic diversity was
studied both within a variety (among seed lots
of a variety) and among varieties (among sets
of seed lots bearing different names). Fourteen
of the twenty-six cultivars identified by
farmers were selected for analysis based on
their origin (all six local varieties and eight
foreign varieties) and seed availability. The
number of seed lots per cultivar (one to six)
varied according to the importance of the
cultivar in terms of planted area.

Morphological descriptors were measured in a
controlled experiment of maize grown in pure
stand in three complete blocks. The experiment
was established in a farmer's field during the
1991 dry season. Each elementary plot (one
seed lot) contained six rows, 5 m in length and
separated by 0.75 m, which conforms to the
spacing most commonly used by farmers in the
study region. Seed for each plot was taken
from 100 ears (2 grains per ear) selected by the
owner. Descriptors were measured using a











sample of 20 plants and 15 ears per elementary
plot, and refer to characteristics of the
vegetative parts, tassel, and ear (see Table 2).4

Factorial Discriminant Analysis (FDA) and
Hierarchical Cluster Analysis (HCA)
(STATITCF program) were used to analyze
diversity among the seed lots within varieties
and among varieties. Factorial Discriminant
Analysis distinguishes seed lots (or varieties)
based on the variables for which the ratio of the


Table 2. Vegetative, tassel, and ear
descriptors measured in the maize genetic
diversity study, Cuzalapa, Mexico

Vegetative descriptors
HPL Plant height
HEA Ear height
DIA Stalk diameter
LLE Length of the leaf of the superior ear node
LLE Width of the leaf of the superior ear node
NLE Number of leaves above the superior ear,
including the leaf of the superior ear node

Tassel descriptors
LTA Tassel length
PED Peduncle length
LBR Length of the branched part of the tassel
BR Total number of branches

Ear descriptors
LEA Ear length
WEA Ear weight
DEA Ear diameter
WCO Cob weight
DCO Cob diameter
ROW Number of rows of grain
HGR Grain height (3 grains mean)
WGR Grain width (10 grains mean)
TGR Grain thickness (10 grains mean)
W1G 1-grain weight (3 samples of 100 grains)


sum of squared differences within a lot (or a
variety) to the sum of squared differences
among lots (or among varieties) is greatest.
Hierarchical Cluster Analysis ranks lots (or
varieties) based on the mean of the weighted
Euclidean distances among their center of
gravity coordinates on the first five axes
identified by the results of the FDA analysis.
All variables were used in the FDA-HCA
analyses except flowering date, grain color,
and 1-grain weight obtained at the sample
level (not at the plant level).

Cultivars and Seed Exchange

Cultivars
As noted earlier, during the six seasons
covered by the survey, survey farmers grew a
total of 26 varieties (Table 3). Each farmer
grew between one and seven maize varieties
during each season and, on average, more
than two varieties per season (Table 1). Most
of these cultivars are white-grained dents with
a floury texture and are used primarily for
making tortillas, the starchy staple of the
Mexican diet. Three flinty popcorn varieties
(Guino Rosquero, Negro [Guino], and Guino
Gordo) were also identified, as well as three
purple-grained varieties (Negro, Negro
[Foreign], Negro Guino) and three yellow-
grained varieties (Amarillo Ancho, Amarillo,
Amarillo [Tequesquitlin]). The purple
varieties are considered sweeter and are
generally consumed roasted at the milky
stage, while the yellow varieties are used
essentially as feed for poultry and horses.5


4 The flowering dates of the different seed lots were also determined by computing regularly the number of plants in
the male flowering (MF) or female flowering (FF) stage. The flowering dates, grain color, and weight per 100 grains
were recorded at the plot level, whereas the other descriptors were measured on each plant and ear of the sample.
5 Farmers associate yellow grain color with richness of oil, a characteristic that interests them for animal feed. The
yellow varieties are not often used as human food because tortillas made from yellow maize are yellowish as if
they had been made with white maize, but using too much lime.











Some varieties have particular agronomic
characteristics. For example, the variety Blanco
matures early and can be harvested early to
free the field for the next cropping cycle.
Varieties with a short growing cycle are grown
primarily in the dry season because of water
shortages toward the end of the season (81% of
the Blanco area was planted in the dry season).
Varieties having a longer growing cycle, such
as Chianquiahuitl, are generally planted in the
rainy season as they are more productive
during this season than varieties with a short
growing cycle (72% of Chianquiahuitl area was
planted in the rainy season). The Amarillo
Ancho variety is considered more productive
than Blanco on piedmont soils. Enano and


Enano Gigante are considered suitable for rainy
season production because their thick stalks
enable them to resist the strong August winds.

Of the 26 varieties grown by farmers, only six
can be considered local based on the definition
used in this study, and all of these are related to
the Tabloncillo race (Table 3). In other words,
only the cultivars Blanco, Chianquiahuitl,
Tabloncillo, Perla, Amarillo Ancho, and Negro
had been grown continuously for at least one
farmer generation in the valley of Cuzalapa.
Chianquiahuitl appears to have been introduced
40 years ago, but the date of introduction for the
other cultivars is unknown.


Table 3. Relative importance of different maize varieties cultivated in Cuzalapa, Mexico

Percentage Percentage
of area planted of Grain
Variety to maize farmers color
Local varieties
White
Blanco 51 59 White
Chianquiahuitl 12 23 White
Tabloncillo 5 6 White
Perla 0.4 0.02 White
Other color
Amarillo Ancho 8 23 Yellow
Negro 3 34 Purple
Foreign varieties
3 most cultivated varieties
Argentinoa 5 10 White
Enanob 3 12 White
Amarilloa 3 11 Yellow
17 minor varieties >3 per >4 per 15 white
Tuxpefo, Tampiquefo, Amarillo [Tequesquitlan], variety variety 1 yellow
Guino Gordo, Guino Rosquero, Negro [Guino], 1 purple
Guino [USA], Blanco [Tequesquitlan], Cosmefo,
Canelo, Ahumado, Negro [Foreign], Tosquefoa
Hibrido [Mejorado], Hibrido, Enano Giganteb
HT47C
Source: Louette (1994).
a Farmers' varieties (landraces).
b Advanced generations of improved varieties.
c First or second generation of an improved variety.










Four of the six local varieties are cultivated by a
large percentage of farmers. Since two of these
varieties have white grain (Blanco,
Chianquiahuitl), one has yellow grain
(Amarillo Ancho), and the fourth has purple
grain (Negro), all four varieties provide for the
different household uses of maize in Cuzalapa.
Although they are few in number, they
dominate the maize area (80%) in the study
zone. The two principal white varieties alone
occupy an estimated 63% of the area planted to
maize. Because of the ways in which the Negro
and Amarillo Ancho varieties are used, they are
cultivated by a fairly high percentage of
farmers (23% and 34%, respectively) in
comparison with the percentage of area they
occupy (8% and 3%).

The remaining 20 of the 26 varieties that
Cuzalapa farmers grew during the survey
period are classified as foreign. The
composition of this group of varieties changed
from season to season. Each foreign variety
covered less than 5% of the maize area planted
in each season, and most were cultivated by
only a few farmers at a time. Only three of
these varieties (Argentino, Enano, and
Amarillo) had been regularly cultivated over
the preceding four or five years by a significant
percentage of farmers (10-12%). Most had been
used for the first time recently or during the
survey period and had been planted again once
or twice. Among these, three varieties of the
Reventador race are well known and have been
introduced episodically in the valley. Over the
period of the study, only one cultivar was
abandoned by the group of farmers
interviewed.

The origin of the foreign varieties is often
difficult to ascertain. Farmers are able to
indicate in which community they acquired a
variety but not its true source. Based on the
information collected, foreign varieties can be


classified into three groups: farmers' varieties
(landraces) (15); farmers' advanced generations
of improved varieties (4); and recent
generations of improved varieties (1) (Table 3).
The group of foreign varieties is
morphologically diverse, including white-,
yellow-, and purple-grained materials and
representatives of different races. Most
cultivars were introduced from communities of
southwestern Jalisco, less then 100 km from
Cuzalapa, although the Guino [USA] variety
cultivated by one farmer originated in the
United States. The origin of the improved
cultivars in the group of foreign varieties is
even more difficult to identify, especially if they
were not directly obtained through credit or
they have been replanted for numerous cycles
in Cuzalapa (as, for example, the Enano
variety). Information about the source of the
variety and even its original name can often
disappear or take on a different meaning when
farmers exchange seed: survey farmers believed
that the Argentino variety came from
Argentina, based on its name only.

In general, the data indicate that although the
varieties defined as "local" occupy most of the
cultivated area, maize cultivation in Cuzalapa
depends not only on local materials but also on
a changing and diverse group of foreign
varieties introduced through farmer-to-farmer
exchanges. The next section explains how, in
addition to exchanging the varieties
themselves, farmers exchange particular lots of
seed.

Seed exchange
By detailing the geographical origin of each
farmer's seed lots, for each variety, in each
planting cycle, the frequency of seed exchange
among farmers can be identified and the
pattern of varietal diffusion can be
characterized. During the study period, the
survey farmers sowed maize in six cropping













they cultivated, survey farmers planted 484 farmers or regions. On average, for all cropping
seed lots (Table 4, Figure 2). seasons, survey farmers selected slightly over



Table 4. Origin of seed lots used in Cuzalapa, Mexico (by variety)

Seed lots Seed lots
acquired in acquired in another
Number Own seed lots Cuzalapa Valley community
of
Variety seed lots (No.) (%) (No.) (%) (No.) (%)

Local varieties
Blanco 139 67 48.2 51 36.7 21 15.1
Negro 79 57 72.2 21 26.6 1 1.3
Amarillo Ancho 54 25 46.3 26 48.2 3 5.6
Chianquiahuitl 53 39 73.6 14 26.4 0 0.0
Tabloncillo 14 8 57.1 5 35.7 1 7.1
Perla 3 2 66.7 0 0.0 1 33.3
Total 342 198 .. 117 .. 27
Mean .... 57.9 .. 34.2 .. 7.9

Foreign varieties
Major varieties
Amarillo 26 13 50.0 11 42.3 2 7.7
Enano 27 12 44.4 14 51.9 1 3.7
Argentino 23 7 30.4 15 65.2 1 4.3
Total 76 32 .. 40 .. 4
Mean .... 42.1 .. 52.6 .. 5.3

Minor varieties
Hibrido [Mejorado] 11 1 9.1 7 63.6 3 27.3
Tuxpeio 8 1 12.5 0 0.0 7 87.5
Amarillo [Tequesquitlan] 6 5 83.3 0 0.0 1 16.5
Hibrido 5 5 100.0 0 0.0 0 0.0
Enano Gigante 5 2 40.0 2 40.0 1 20.0
Guino Gordo 5 2 40.0 1 20.0 2 40.0
Guino Rosquero 4 2 50.0 0 0.0 2 50.0
Negro [Foreign] 4 1 25.0 3 75.0 0 0.0
Blanco [Tequesquitlan] 3 2 66.7 0 0.0 1 33.3
Guino [USA] 3 2 66.7 1 33.3 0 0.0
HT47 3 2 66.7 0 0.0 1 33.3
Cosmeho 2 0 0.0 1 50.0 1 50.0
Tampiqueno 2 0 0.0 0 0.0 2 100.0
Canelo 2 0 0.0 1 50.0 1 50.0
Ahumado 1 1 100.0 0 0.0 0 0.0
Negro [Guino] 1 0 0.0 0 0.0 1 100.0
Tosqueno 1 0 0.0 0 0.0 1 100.0
Total 66 26 .. 16 .. 24
Mean .... 39.4 .. 24.2 .. 36.4

TOTAL 484 256 .. 173 .. 55
MEAN .... 52.9 .. 35.7 .. 11.4

Source: Louette (1994).


cycles on 442 ha. For the total of 26 varieties


Many of these seed lots came from other











half (53%) of their seed lots from their own
harvest. About 36% of the seed lots were
obtained from another farmer in Cuzalapa, and
11% were introduced from other regions.
Calculated in terms of area planted, seed from
farmers' own harvests represented 45% of the
maize area in the study zone, whereas 40% was
planted to seed from other Cuzalapa farmers
and 15% was planted to foreign introductions.
Seed exchange whether between farmers
inside the valley or with farmers outside the
valley is clearly very important.

The pattern of varietal diffusion
Both local and foreign varieties were planted
from farmers' own seed lots, seed lots acquired
in Cuzalapa, and introduced seed lots, but in
different proportions. Significant differences in
origin were associated with the dominance of
the variety in terms of planted area. Seed of the
most widely grown varieties including the
local varieties and the three most important


60-5-


0
U 40-
0
2 30-
--
1 20-

10-

0-


Local varieties


Foreign varieties
Major Minor


S Own seed
- Seed acquired in Cuzalapa
[ Seed acquired in another community


% of lots
52.9
35.7
11.4


% of area
44.9
39.9
15.1


Figure 2. Origin of maize seed planted in
Cuzalapa, Mexico, by origin of variety (29
farmers, 6 cropping cycles).


foreign varieties is less likely to have been
obtained from farmers outside Cuzalapa than
seed of the more minor foreign cultivars (7.9%
of local and 5.3% of important foreign seed lots
were introduced, compared to 36% of minor
foreign seed lots) (Figure 2).

Seed of local varieties is essentially reproduced
by each farmer. Among local varieties, seed for
Chianquiahuitl and Negro is managed more
conservatively; more than 70% of the seed for
these varieties is selected from farmers' own
maize harvests (Table 4). In fact, farmers plant
such a small area to the variety Negro that, on
average, seed equivalent to only 27 ears is
required per farmer (Louette 1994). This
amount of seed, in good condition, is carried
over easily from one cycle to the next, and
farmers do not need to seek out seed from
another farmer. Chianquiahuitl is a variety of
unknown origin that is no longer believed to be
widely cultivated outside the study zone, so of
necessity farmers in the Cuzalapa Valley must
rely on their own stocks.

The case of Blanco contrasts with that of
Chianquiahuitl. Of all the local varieties, Blanco
has the highest proportion of seed obtained
from farmers outside the study zone (15%).
This result reflects the importance of Blanco in
terms of area cultivated in Cuzalapa and
regions nearby. Because Blanco is important for
household subsistence, an insufficient number
of ears suitable for seed may remain at planting
time. Farmers then search for seed from other
farmers in and outside the community. In fact,
the data suggest that an informal contractual
relationship may exist between farmers in
Cuzalapa and in Chacala, located 30 km away.
Of the 21 lots of seed for the variety Blanco
introduced during the study period, about half
(11) originated in Chacala, and nine of them
were sown in the dry season. On the other
hand, Chacala farmers come to Cuzalapa to










obtain seed to plant Blanco in the rainy season
(there is no irrigation in Chacala).

Although the percentage of seed brought from
other regions is small for the most widely
grown foreign varieties, farmers in the valley
exchange seed of these varieties quite
frequently (Figure 2). These varieties were
introduced some years ago, and because they
have demonstrated characteristics of value,
their seed is redistributed to other farmers in
Cuzalapa. For example, increasing interest in
the variety Argentino was observed during
the study period, and farmers acquired 65% of
the seed for this variety from other farmers in
the study zone (Table 4).

The situation is less clear for foreign varieties
that are minor in terms of cultivated area.
Each variety appears to be a special case
defined by the time of its introduction and the
number of farmers planting it. For some of the
varieties introduced late in the survey period,
all seed lots were introduced. On the other
hand, because farmers test foreign varieties
over several seasons, reproducing them
locally, 39.4% of the seed of introduced
varieties was selected from farmers' own
harvests. Relative to the major foreign
varieties, the proportion of seed of minor
foreign varieties that was obtained from other
farmers in Cuzalapa is small. Presumably,
survey farmers who did not plant these
varieties during the study period are not yet
convinced of their advantages.

In summary, there is a moderate level of
diffusion of local varieties inside the
watershed and little infusion from other
regions. Recently introduced foreign varieties
are infused from outside the valley. Older
foreign varieties that have attained a moderate
level of acceptance are also diffused inside the
watershed. The pattern of diffusion of the


varieties is therefore linked essentially to the
local acceptance of the variety, the time it has
been sown in the region, and the availability of
seed inside and outside the region.

Farmer type
The general patterns of maize seed exchange
that we have just described nevertheless
conceal major differences among survey
farmers. At one extreme are the farmers who
use seed selected from their own maize
harvests almost exclusively from one season to
the next (Figure 3). At the other end of the
spectrum are farmers who have never used
their own seed lots. An intermediate group of
farmers use their own seed and seed from other
sources.

Farmers who almost always use their own seed
lots sow the same varieties regularly and only
modify the proportion of maize area planted to


0 m r
100-90 90-70 70-40 40-20 20-10 0
Percentage of own seed lots
Number of farmers per class
3 8 8 5 8 7
Own seed 7 Seed acquired in Cuzalapa
I | Seed acquired in another community
Figure 3. Classification of the 39 farmers
surveyed in Cuzalapa, Mexico, by the origin
of their maize seed (6 cropping cycles).










each variety in each cropping season. These
farmers are considered suppliers of seed of
local cultivars ("they always have seed").

Other farmers use their own seed lots as well as
seed acquired in the community or introduced
from other regions, and the proportions of each
type of seed vary from season to season
depending on each farmer's objectives and
constraints. These farmers are generally
regarded as suppliers of introduced seed, and
some are known in the community for their
curiosity about new varieties.

The farmers who used almost no seed from
their own maize harvests had recourse
throughout the study period to seed acquired
within and outside the Cuzalapa community.
This group of farmers includes those who do
not have rights to land and cannot plant maize
each season and those who farm small areas on
which they cannot harvest enough maize for
both family consumption and seed. Farmers in
this group are obliged to look for seed from
other farmers when they want to plant maize.

A relation exists between the number of
varieties (different seed lots) sown by each
farmer in each cycle and farmer type. The
correlation coefficient between the number of
varieties per cycle and the proportion of the
farmer's seed stocks originating from his own
harvest is 0.5. In general, farmers who have
more recourse to seed produced by other
farmers appear to plant fewer varieties per
cycle. The group of farmers who sowed more
than 90% of their crop with seed from their
own harvests planted an average of 2.6
varieties per cycle, while those who used no
seed from their own harvests planted an
average of only 1.3 varieties per cycle. This
finding may reflect either a greater reliance on
diverse maize types by more conservative


farmers, or it may reflect the fact that searching
for seed from other farmers requires more
effort and is therefore associated with fewer
varieties sown.

Factors explaining seed exchange
Several factors induce farmers to exchange
seed. The first is the traditional method of seed
storage. Maize (for seed and for food) is stored
in bulk in a room of the house. Ears are often
attacked by weevils and other insects when the
grain is stored for longer than six months (from
one dry season to another dry season, for
example). If a farmer sows a particular variety
in only one season per year and has not sown
that variety in the previous year, or if the
cropping calendar obliges him to plant before
harvest, he will search for seed from ears that
have been harvested more recently by other
farmers. The dry season is better for providing
seed because more area is cultivated. Either as
a percentage of area planted or as a percentage
of total seed stocks, the interchange of seed is
more evident at the end of the rainy season. For
example, farmers' own maize harvests provide
32% and 57% of the seed for Blanco and
Chianquiahuitl grown in the dry season and
69% and 81% of the seed for these varieties
during the rainy season.

A second important factor affecting the
importance of farmers' seed sources in planting
decisions is the socioeconomic status of the
household, as represented by farm size, land
use rights, and access to the market for renting
land. As noted above, many farmers do not
cultivate an area large enough to meet their
annual food consumption needs, whereas
others own no land and must rent a field to
cultivate maize. These farm households often
consume all of one season's production before
planting and are obliged to search for seed each
season.










Another factor influencing the seed sources
used by farmers is the custom in the Cuzalapa
region of producing maize under
sharecropping arrangements. Under these
arrangements, the partner (or mediero)
generally supplies labor while the field owner
(or patron) supplies the inputs in particular,
maize seed. Generally the mediero does not
choose which varieties to plant, and at harvest
time acquires seed from the patron, who is
recorded in this study as "another farmer of the
region." Seed is also loaned, under the proviso
that double the quantity of seed loaned must be
returned at harvest. In either case, the farmer
obtains maize seed of a variety that another
farmer has chosen to grow and that is derived
from another farmer's harvest.

Another finding from the survey is that few
farmers expressed any particular preference for
or allegiance to their own maize as a source of
seed. Seed of a given variety selected from their
own maize harvest or acquired from other
farmers was considered equivalent. In other
words, another farmer's method of seed
management was not a cause for concern.
Furthermore, if a farmer does not grow a
particular variety for several successive
seasons, this does not signal that the farmer has
ceased cultivating it altogether, as long as the
seed for that cultivar can still be obtained from
other farmers if necessary. Farmers also
generally consider that they must change seed
regularly to maintain the productivity of the
variety ("sow the same maize type but from
new seed"). The frequency of seed renewal
varies from several cycles to several years. It
appears unlikely that any farmer in Cuzalapa
sows seed derived from a stock bequeathed
directly from his parents.


Finally, farmers appeared to be very curious
and open-minded, in general, about testing new
cultivars. After visiting a relative or friend, or
after harvesting a maize field as a laborer, a
farmer often returns with maize ears so that he
can test a variety whose ear characteristics he
admires. The introduced seed lots acquired
from other farmers are almost never bought as
seed. They are gifts from friends or family
members living outside the zone or are selected
from maize cobs bought for consumption.

Phenotypic Diversity of Varieties

The patterns of maize production and seed
management described above are characterized
by continual introductions of varieties and,
within varieties, considerable exchange of seed
among farmers. These findings raise questions
about the structure of maize diversity in the
Cuzalapa watershed. For example, how can an
introduced seed lot be integrated into a local
variety? Do foreign varieties compete with local
varieties or are they complementary? Analyses
of the phenotypic diversity of maize grown in
Cuzalapa provide a way to examine some of
these questions.

Phenotypic characteristics and
varietal identification
With the exception of the B1 lot of the Blanco
variety, the HCA analysis of seed lots for the
five most important varieties (four locals and
one foreign) demonstrates that seed lots bearing
the same name cluster together based on their
morphological characteristics (Figure 4).6 The
results support the hypothesis that farmers'
concept of a variety corresponds closely to that
of a phenotype. A farmer variety is a set of seed
lots having the same name; these seed lots


6 If grain color had been used as a variable in the analysis, the seed lots of the Amarillo Ancho (AA) and Negro (N)
varieties that now appear within this group would have been differentiated.











produce maize with similar plant, tassel, and
ear characteristics.

The implication of these findings is that when
farmers in Cuzalapa classify seed as that of a
given variety they use morphological and
phenological criteria rather than criteria such as
geographic origin, adaptation to some limiting
factor, or ritual function. A seed lot that
resembles seed of a "local" landrace is classified
as such by the farmer, even though its origin
may be foreign or unknown. As a consequence,
some seed lots of "local" landraces are in fact
introduced from other regions. Furthermore,
the composition of the group of seed lots that
constitute a variety is mutable over time.

Phenotypic variation between varieties
The phenotypic characteristics of six local
varieties and eight foreign cultivars (including
the three most widely cultivated) were studied
with the methods described above (Table 5).


Amarillo Ancho (AA), Negro (N), and Blanco 1 (B 1)
AA1
N2- Short
B1 growing
AA2 cycle
AA4
AA3
N3
N1
Blanco (B)(except B1)
B4
B6 -
B2
B3
B5
Chiaquiahuitl (C)


C3
C4- I
C1
C5
Argentino (AR)


Long
growing
cycle


AKZ|
AR3

Figure 4. Hierarchical Cluster Analysis of
seed lots of five varieties by phenotypic
characteristics.


The data reveal a large amount of phenotypic
diversity with respect to several characters. For
example, the sum of degree days from sowing to
tasseling varied from 1,1300C for the earliest
maturing variety, Blanco, to 1,5500C for the latest
maturing variety, Argentino (Blanco required 77
days to reach maturity during the 1991 dry
season and Argentino required 96 days). Mean
height of the ear varied from 129 cm to 195 cm,
the number of rows of grain varied from 8.7 to
12.7, the grain width from 0.85 cm to 1.13 cm, the
cob diameter from 1.8 cm to 2.7 cm, and the ear
weight from 104 g to 181 g.

In the varieties studied, 78% of the variability in
phenotypic characteristics was explained by the
first two axes of the FDA (Figure 5). The first axis
is essentially defined by row number (-ROW),
grain width (+WGR), plant height (-HPL), and
ear height (-HEA). The second axis is determined
by ear development, including the weight and
diameter of the cob (+WCO, +DCO) and weight


Axis 2 20.0%
-WCO -DCO
-WEA -DEA


Long Short
growing o growing
cycle cycle


-1.5 -1 -0.5 0 0.5 1 1.5

Axis 1 57.6% -ROW-HEA-HPL+WGR-BR-NLE

Figure 5. Phenotypic diversity of maize
varieties planted in Cuzalapa, Mexico:
Factorial Discriminant Analysis of
vegetative, tassel, and ear characteristics,
axes 1 and 2.
Note: Local varieties in large characters; key to
descriptors and varieties in Tables 2 and 5.











and diameter of the ear (+WEA, +DEA). A test
comparing farmers' methods for identifying
varieties and these two axes indicated that the
statistical analysis and farmers classify maize
varieties in a similar way (Louette 1994).

The descriptors listed above facilitated the
differentiation of varieties in two ways: by
duration (length of growing cycle) and by
origin or race. These characteristics were not
included as variables in the analysis because
they characterize each seed lot but not each
plant or ear, but they were closely related to
some descriptors that define the first two axes


of the FDA. Duration is highly correlated with
descriptors for the first axis (r>0.80 between
male flowering date and HEA, NLE, WGR,
ROW). A long-duration variety is characteristically
a taller plant that has more leaves and smaller
grains arranged in more rows.7

The origin of a variety (local or foreign) also
relates to differences in phenotypic
characteristics. The only exception to this general
rule is the variety Amarillo [Tequesquitlan] (AT),
which is associated with the local varieties even
though it was introduced from a community
located some 20 km from Cuzalapa. The local


Table 5. Principal characteristics of the 14 varieties studied in Cuzalapa, Mexico (local
varieties in boldface type)

MF HEA HPL WLE WGR TGR WCO DCO WEA DEA W1G
Variety (days) (cm) (cm) NLE (cm) BR ROW (cm) (cm) (g) (cm) (g) (cm) (g)

Short duration

Blanco (B) 77.3 129 219 5.9 7.9 16.1 8.7 1.13 0.40 19.7 2.1 140 4.0 0.42

Intermediate duration

Perla (P) 82 144 235 6.1 8.1 16.9 8.7 1.08 0.39 18.7 2.2 128 3.9 0.38
Amarillo Ancho (AA) 82 146 231 6.1 7.9 19.3 9.8 1.00 0.39 19.8 2.2 126 3.9 0.33
Amarillo [Teq.] (AT) 82 160 242 6.2 7.8 20.8 9.6 0.99 0.38 17.5 2.1 123 3.9 0.35
Negro (N) 83.2 156 232 6.3 7.9 19.8 10.0 0.97 0.37 18.1 2.2 123 3.9 0.31
Tabloncillo (T) 85 145 230 6.2 7.7 19.2 9.3 0.95 0.33 12.0 1.8 104 3.6 0.29

Long duration

Negro [Foreign] (NX) 91.5 171 232 6.1 8.2 20.5 10.2 1.00 0.38 23.1 2.4 126 4.0 0.31
Hibrido (H) 92 179 254 6.3 8.1 20.4 11.9 0.91 0.37 22.0 2.3 141 4.2 0.30
Amarillo (A) 92 185 261 6.6 8.1 19.8 11.3 0.99 0.38 27.3 2.6 164 4.4 0.36
Enano (E) 92.5 161 231 6.8 8.5 23.2 13.4 0.89 0.40 29.7 2.7 160 4.5 0.31
Guino (G) 92.5 174 249 6.5 8.6 20.0 12.7 0.94 0.36 30.1 2.7 181 4.6 0.34
Chianquiahuitl (C) 93.2 188 260 6.2 7.8 21.5 11.7 0.85 0.34 17.6 2.1 126 3.9 0.27
Enano Gigante (EG) 93.5 185 261 6.6 8.4 20.5 12.4 0.93 0.36 26.2 2.6 158 4.4 0.32
Argentino (AR) 96 195 273 6.5 8.4 22.8 12.6 0.92 0.36 26.2 2.5 158 4.4 0.32

Source: Louette (1994).
Note: MF = male flowering date; HEA = ear height; HPL = plant height; NLE = number of leaves above the superior ear,
including the leaf of the superior ear node; WLE = width of the leaf of the superior ear node; BR = total number of
branches of the tassel; ROW = number of rows of grain; WGR = grain width (10 grains mean); TGR = grain
thickness (10 grains mean); WCO = cob weight; DCO = cob diameter; WEA = ear weight; DEA = ear diameter;
and W1G = 1-grain weight (3 samples of 100 grains).

7 Length of growing cycle is, as expected, significantly different between the short-duration and long-duration groups
of varieties (p<5%).










varieties are characterized by narrower, lighter
ears and less vegetative development than the
foreign varieties (Table 4). They and Amarillo
[Tequesquitlan] are related to the Tabloncillo
race, which originated on the Pacific Coast of
Mexico (Wellhausen et al. 1952). The foreign
varieties included in the trial (excepting AT) are
linked to other races. Origin is therefore related
to variation in race.

Origin and duration are also interrelated. Most
of the varieties with long growing cycles are
foreign, with the exception of Chianquiahuitl.
In Cuzalapa, therefore, local and foreign
varieties appear to be complementary from a
morphophenological point of view. Most local
varieties have a short growing cycle, reduced
vegetative development, few rows, and large
kernels, whereas introduced varieties have a
long growing cycle, taller plants, and small
kernels.

There are three possible explanations for the
fact that foreign varieties in Cuzalapa almost all
have long growing cycles, whereas local
varieties have short ones. The first is that in
Cuzalapa today, varieties with a short growing
cycle are grown primarily in the dry season and
long-cycle varieties are generally planted in the
rainy season. Until the 1970s, flooded rice was
cultivated during the rainy season and maize
was sown almost exclusively during the dry
season. The local landraces were then generally
early maturing. The longer growing cycles of
foreign varieties may reflect the fact that maize
began to be cultivated during the rainy season
only recently.

Another explanation for the close relationship
between length of growing cycle and foreign
origin is that few landraces in the region around
the Cuzalapa Valley mature early, because
outside Cuzalapa the major cropping cycle is
the rainy season. On the other hand, few early


maturing improved varieties have been
developed for the lowland tropical zones
where most maize is produced in developing
countries; one of CIMMYT's objectives is to
develop materials with such characteristics
(CIMMYT 1993).

Finally, the complementary characteristics of
local and foreign varieties may be interpreted
in yet a different way. When a lot of seed
introduced from another community has the
same phenotypic characteristics as seed of a
local variety, farmers may consider it as seed of
a local variety. The new seed would be
identified by the name of the local variety and
would no longer be distinguishable from it. For
example, all introduced seed of maize with
short, thick stalks is named Enano after the first
foreign variety that had that kind of stalk.
Farmers appear to use different names only for
seed lots with particular characteristics of
interest for them. No introduced seed lot that is
morphologically similar to a local variety
would be distinguished, so no foreign variety
with characteristics similar to those of local
varieties would be recognized as a distinct
cultivar.

Discussion

In the Cuzalapa region, farmers cultivate a
large number of varieties that are diverse with
respect to vegetative characteristics, ear
characteristics, and length of growing cycle.
Phenotypic diversity seems to be an adaptation
to the opportunity in Cuzalapa of producing
maize during two seasons each year, each with
distinct pedoclimatic conditions. It also reflects
the diverse uses of maize and multiple
objectives of farm households in the region.
The observations reported here confirm the
widespread image of great diversity and
multiple production strategies in traditional
cultural systems (Merrick 1990, Toledo 1990).










The assumption that traditional systems are
closed and isolated with respect to the flow of
genetic material is clearly contradicted,
however, by the results of this study. The
group of maize varieties cultivated by farmers
in the traditional community of Cuzalapa
changes in composition over time. A small
group of local landraces is continuously
cultivated, while varieties with diverse origins
that are morphologically diverse among
themselves and distinct from the local
landraces succeed each other over time. These
foreign varieties are introduced for testing by
farmers, but they may also be integrated into
the group of local landraces.

Rather than displacing local cultivars, foreign
varieties occupy a small proportion of the area
planted to maize, and local landraces continue
to dominate maize area in Cuzalapa. Similar
results have been reported by researchers
investigating the use of rice (Dennis 1987),
maize (Ortega 1973), and potato varieties
(Brush et al. 1981) in their regions of origin.
Introduced varieties more often have uses and
modes of management that are
complementary, rather than substitutable for,
those of the dominant cultivars (Berard et al.
1991). In Cuzalapa the morphophenological
characteristics of the local and foreign varieties
seem complementary, and the two groups
rarely compete with respect to growing cycle,
vegetative characteristics, or ear attributes.
Introductions do not necessarily lead to a large
shift away from local cultivars. This finding
suggests that a variety is more easily adopted
by farmers if it satisfies a need that is not
currently met by local varieties or if it occupies
a place in the morphological continuum that
has not yet been exploited (Boster 1985). In
Cuzalapa, survey farmers clearly sought new
or different genetic materials from among
foreign varieties.


At the level of introduction observed in
Cuzalapa, foreign varieties are more a source of
phenotypic diversity than a cause of genetic
erosion. As indicated by Brush (1992), genetic
erosion seems to be a phenomenon that is too
complex to be captured in the equality
"introduction of varieties = loss of genetic
diversity." Genetic erosion is a complex
function of the area occupied by introductions
versus area planted to local cultivars, the
diversity within and between the introductions
and local cultivars, and the extent to which
local varieties have been abandoned or
substituted. As long as the function of the
introduced material is complementary to that
of the local germplasm, diversity probably
increases. When the introduced and local
materials compete, foreign varieties can
displace local material, but this displacement
necessarily leads to a loss of diversity only if
the introduced material is less diverse or
replaces several local landraces. Identifying
accurately the factors that affect the extent of
genetic erosion, and determining their critical
values, is likely to be difficult, and especially so
in a system as dynamic as that of Cuzalapa.

Research findings have implications for how
and when adoption occurs. The regular
introduction of genetic material by farmers is
evidence of their curiosity about, rather than
resistance to, the introduction of new cultivars.
In Cuzalapa, farmers are generally
experimenters who do not hesitate to test new
cultivars they have seen planted by farmers in
other regions against their dominant local
varieties. Farmers will adopt a maize variety,
however, only if it demonstrates its advantages
consistently over a large number of cropping
seasons. One trial with bad results can lead a
farmer to abandon a variety, regardless of the
reason for the failure. During the last 40 years,
of all of the varieties introduced by the survey
farmers of Cuzalapa, only Chianquiahuitl has










been adopted. Brush et al. (1981) have also
indicated that in the Mantaro Valley in Peru
farmers may travel more than 50 km in search
of new potato varieties. In Dennis' (1987) study
in Thailand, the average farmer in the eight
villages cultivated 10 varieties in the first year,
adopted four introduced varieties in five years,
and abandoned four cultivars during the same
period. Dennis characterizes similar situations
as an "excess of diversity" with respect to what
is necessary to keep the agricultural system
functioning.

Another major research finding concerns the
definition of a local variety itself. The
magnitude of seed exchange among farmers
raises questions about farmers' concept of a
variety, the meaning of "local," and the
distinction between "local" and "foreign"
varieties. First of all, in Cuzalapa, it is not only
the set of cultivars but also the set of seed lots
that constitutes the cultivars that varies in time.
A certain number of seed lots disappear in each
crop cycle because they are not replanted by
the farmer who selected them; on the other
hand, one introduced seed lot may evolve into
a number of seed lots, once farmers begin to
exchange seed. Introduced seed lots that
phenotypically resemble seed of local landraces
are integrated into them. A farmer variety is
therefore mutable in terms of the number,
origin, and genetic composition of the seed lots
that compose it. In and of themselves, local
varieties constitute systems that are genetically
open.8

The geographical point of reference for the
term "local variety" is revealed to be larger
than the community itself. The genetic
diversity of a variety is traceable to more than
the community itself, because seed lots of


external origin are regularly added to those of
local landraces that are then locally
reproduced. This practice may be a means for
adding diversity to locally adapted cultivars.

Implications for In Situ
Conservation

The characterization of the maize farming
system in the Cuzalapa watershed as open with
respect to genetic material is in contrast with
the original model for conserving crop genetic
resources in situ. This model was based on the
belief that the best means for in situ
preservation of the diversity found in genetic
material was to isolate it in space and time by
maintaining intact the technical, social, and
cultural context in which it occurs (Iltis 1974,
Benz 1988). According to this point of view, it is
necessary to "freeze" the genetic landscape by
fixing its environment in parks or reserves
where the cultivation of local varieties would
be encouraged and where the introduction of
foreign cultivars and of new techniques would
be prohibited (Iltis 1974). From this point of
view, the evolution of a cultivar is considered
to be determined exclusively by the region in
which it is cultivated and by the traditions of a
rural community (Hernindez X. 1988, Benz
1988). Conserving the diversity found in local
cultivars therefore requires maintenance of the
cultural techniques used by farmers and of the
broader social context. Development is
therefore counterposed with conservation. The
dimensions of the farming system in a region
are not perceived as affected by exchange with
other communities, nor is a variety perceived
as the product of genetic exchange with
materials that may or may not be replanted
locally.


8 One purpose of ongoing research in Cuzalapa is to analyze the concept of a farmer's variety by studying how seed
selection and management practices influence genetic structure.










Instead, this case study shows that over three
years alone, in a traditional farming system
located in what some regard as the
geographical center of origin for maize,
introduced materials represent a substantial
proportion of the maize seed planted. The
study further shows that local varieties are not
generally the product of exclusively local seed
selection and management, because farmers
exchange seed of local varieties with other
farmers within and outside the region.

The findings raise important questions about
the best way to conserve the diversity in crop
genetic resources. The appropriate geographic
scale over which we can define a variety as
"local" becomes a concern. The mechanisms
that explain the phenotypic diversity of maize
in Cuzalapa suggest that a certain influx of
genetic material rather than isolation is
occurring. Foreign varieties, as well as
introduced seed lots that are then integrated
into local varieties, are probably a source of
phenotypic and genetic diversity. The Blanco
cultivar is not only the result of local seed
selection by local farmers but also of selection
by farmers and natural selection in other
regions (in particular Chacala). It is
questionable whether any particular
geographic scale would necessarily include all
of the factors affecting the variety. The strategy
of isolating a region on grounds that
introduced seed will displace local varieties or
even lead to alterations in their genetic


structure seems inconsistent with the
mechanisms that generate the diversity we
observe in the fields of farmers who cultivate in
traditional systems.

Some conservationists may argue that if the
community under study reveals these
characteristics, it is not traditional, because
traditional systems are autarkic. In fact, the
characterization of a society or community is
normative and relative: a community is
traditional only with respect to what is
perceived as modern and with respect to other
contemporary human groups. In any case, the
system of seed exchange that has been
described by farmers and observed in Cuzalapa
appears "traditional" in the sense that it is
customary and long-lived. It is likely that the
major findings reported can be generalized to
other rural areas of Mexico, because the factors
that explain the seed exchange system in
Cuzalapa appear neither new nor specific to
this region. To be convinced of this point it is
enough to observe the extent to which world
agriculture in general is the fruit of an ancient
and continuous evolution that includes the
diffusion of plants from their centers of
domestication, the adoption and abandonment
of cultivars or of cultivated plants, the
differentiation of races and varieties within
species, and the adaptation of cultivars to
various agrosystems and techniques of
cultivation (Haudricourt and Hedin 1987;
Harlan 1992).











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