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1 dT UNIVERSITY OF FLORIDA
S7--3 INSTITUTE OF FOOD AND AGRICULTURAL SCIENCE HU ME BRARY
AGRICULTURAL RESEARCH AND EDUCATION CENTER ME
33505 MAR 72
Mimeo Report GCS71-3 January, 1971Fr
BREEDING FRESH MARKET TOMATOES FOR MACHINE HARVEST IN niv. of
Pat Crill, D. S. Burgis and J. P. Jones
The Florida tomato breeding program was established in 1924 at the
University of Florida Tomato Laboratory in Palmetto, Florida, at the request
of the growers led by Mr. J. P. Harlee, Sr. Leaders of this new program
were Dr. George Weber (Plant Pathologist) and Mr. David G. A. Kelbert (Horti-
culturist). Objectives of the tomato breeding program were to develop varie-
ties culturally adapted to Florida environmental conditions and resistant
to the prevalent diseases. The most serious diseases in 1924 were Fusarium
wilt and an unknown foliage disease complex. Weber began work on the un-
known complex and in a series of experiments demonstrated several specific
pathogens were involved (6,7). He differentiated between Alternaria tomato
nailheadd rust), Alternaria solani (early blight) and Stemphylium solani
(gray leafspot). These basic fundamental plant pathological studies formed
the basis of the breeding program. Weber isolated resistance to nailhead
rust and incorporated this resistance into Fusarium wilt tolerant breeding
lines. lie and Kelbert eventually released three varieties, NEWELL, CARDINAL
KING and RUbY QUEEN, which were very tolerant to Fusarium wilt and resistant
to nailhead rust (Table I.). Weber also supplied breeding lines to other
tomato breeders who utilized these resistances in their programs.
If varieties had not been developed which possessed these disease re-
sistances, Florida's tomato industry would never have developed into the
$100 million crop it is today. Nailhead rust has never been a problem since
resistant varieties were released, and the pathogen causing this disease is
evidently extinct. Because of his expertise in all areas of plant patho-
logy George Weber was forced to leave the tomato breeding program and concen-
trate his efforts in other areas, including guiding the American Phyto-
pathological Society in various capacities from regional offices to national
The responsibilities of the Florida tomato breeding program were next
assumed by Dr. A. L. Harrison, another plant pathologist. Harrison did not
develop any varieties during his short stay in Florida, but he did collect
and classify a large number of genetically controlled disease resistances.
Included were resistance to gray leafspot, Cladosporium leaf mold, race 1
Fusacium wilt and tolerance to early blight. In 1946 Dr. Harrison was offered
the opportunity of conducting a tomato breeding program for the Texas Agri-
culture Experiment Station. He accepted this challenge and left Florida
for Yoakum, Texas, where he has conducted a very successful program in breed-
ing for disease resistance.
The late Dr. James M. Walter arrived in Florida in January of 1947 when
he accepted the responsibility of deVeloping tdmato varieties that were
horticulturally acceptable 6a well ap resiotaht to the diseases common in
Florida. During Walter's tenure at the Gulf Coast Experiment Station,
Florida became an internationally known center of activity for tomato re-
search. Dr. Walter was responsible for the creation of 13 named varieties
of tomato which are grown in all countries of the world (Table I.). He also
supplied genetic material to all who requested it and thus made a further
impact in the field of tomato breeding. Dr. Walter's greatest accomplishment,
perhaps, was to demonstrate that varieties could be developed which were not
only horticulturally acceptable but resistant to a large number of diseases.
At the time of his death Dr. Walter had developed genetic stocks of superior
horticultural qualities that were also resistant to at least 14 different
pathogens. No other plant breeder or plant pathologist could lay claim to
such a feat, but many will have the opportunity to do so in the future because
of Dr. Walter's efforts. In retrospect, his contributions to breeding for
disease resistance are even more impressive when one becomes familiar with
the modest facilities with which he worked.
In 1948 Dr. A. P. Lorz joined the Vegetable Crops Department of the
University of Florida and initiated a program to complement Dr. Walter's
program. Intensive research was also being carried on in other areas of the
state. Dr. R. A. Conover at the Sub-gropical Experiment Station in Home-
stead demonstrated Verticillium wilt was a limiting factor in South Florida
tomato production. Dr. Conover concluded the best method of controlling
Verticillium wilt was to isolate genetic resistance and incorporate this in-
to the tomato breeding program. He began the search for sources of resis-
tance and was instrumental in creating another tomato breeding position for
the University of Florida. This position was filled by Dr. James W. Strobel
in 1958. Strobel's immediate success at this position is indicated by the
three Verticillium wilt resistant varieties he developed; TROPIC, TROPI-RED
and TROPI-GRO(Table I.).
With the untimely death of Walter, Strobel assumed leadership of the
tomato breeding work for the University of Florida and released the first
race 2 Fusarium wilt resistant variety which he named WALTER in honor of Dr.
James M. Walter. Another of Strobel's contributions to the Florida tomato
breeding program was the tremendous amount of germ plasm he collected and
the cooperative agreements he entered into with other tomato breeders around
the world. Administrative leaders of the University of Florida recognized
Dr. Strobel's talents and named him Head of the Gulf Coast Experiment Station
in 1968 and then Chairman of the Department of Ornamental Horticulture in
When Dr. Strobel was named Head of the Gulf Coast Experiment Station
the tomato breeding program at the Sub-Tropical Experiment Station was assumed
by Dr. Ben Villalon. Villalon, like Harrison 25 years earlier, received an
opportunity to return to his home state of Texas and accepted the challenge.
Besides the authors, other University of Florida researchers who are working
in the tomato variety development program include Dr. H. H. Bryan and Dr. R. T.
McMillan of the Sub-Tropical Experiment Station, Dr. P. H. Everett of the
South Florida Field Laboratory, Mr. N. C. Hayslip of the Indian River Field
Laboratory and Dr. J. A. Bartz, Dr. C. B. Hall and Dr. R. E. Stall of the
PROGRESS 'At cufti'Et OBitTiVS.
The primary objective ot the university of Florida tomato breeding
program is the same in 197i as it was 47 yeas ago when first defined by
Dr. George Weber; to develop multiple-disease resistant vdtieties adapted
to Florida cultural conditions: This same objective is being applied to
solve the vastly different disease dad cultdual pFdbles of the present.
Likewise, the objective of the Florida tomato breeding program of the future
will also be the same.
Drs. Strobel and Walter very early recognized the need to develop fresh
market tomato varieties which could be completely mechanized from planting
through harvesting and they began working to this end in 1965. Several
genes involving fruit separation were investigated including the normal joint-
ed, jointless 1, jointless 2 and cin cin 2. All tests indicated jointless 2
(J2) was superior. The expression of J is controlled by a single recessive
gene; however, the ease or difficulty of separation is apparently poly-
genically controlled. Most of the early segregates were discarded because
fruit separation was not satisfactory. Evaluation of hundreds of lines has
been conducted using a shaker device developed by Professor W. W. Deen, an
agricultural engineer at the Everglades Experiment Station. The most promis-
ing lines now appear genetically stable and fruit free of stems separate
easily from the vine without shattering. In actual machine harvested plots
90% stemless fruit are obtained from most of the promising variety candidates.
Intensive effort was made to combine the J2 with all possible disease resis-
tant genes. In addition, selection pressure was applied to develop a concen-
trated set of crack-free fruit. The ideal concentrated fruit set for machine
harvest results when every flower on every plant in a field attains anthesis
and sets fruit simultaneously. The ideal fruit concentration has not yet
been reached; however, it is being approached since some lines will yield
25-30 marketable fruit which differ only by 7-10 days in the maturation of
the earliest to the latest fruit.
The University of Florida plans to release very shortly a tomato varie-
ty which is adapted for mechanical harvest (probably by July 1, 1971). This
variety will be a short compact determinate plant which will yield upwards
of 500 bushels per acre of marketable fruit. The fruit will separate from
the vine free of stems (90%) but will not shatter. The variety will be
medium early in maturity and produce fruit free from cracking. It will be
resistant to gray leafspot, Verticillium wilt, races 1 and 2 of Fusarium
wilt, and very tolerant to early blight, gray wall, and tobacco mosaic virus
(TMV). The fruit will respond very well to ripening with ethylene and pre-
liminary tests indicate fruit have a very long shelf-life and do not "break
down" as readily as some other varieties.
Release of a machine-harvest variety and the development of a machine-
harvest tomato industry in Florida will create many problems. One which
seems particularly serious is the scheduling of harvests to fit the capabil-
ities of the packing house. Horticulturists are attempting to answer this
problem by scheduled plantings; however, it appears crop maturity can best
be controlled genetically. The ultimate aim of the breeding program is to
produce varieties in six maturity groups which range from very early to very
late. The total time difference in maturity of the six simultaneously plant-
ed varieties would be 30-40 days from the harvest date of the earliest to the
latest. Erratic weather conditions can influence maturity of staggered plant-
- 4 -
ing dates and result in all planting dates maturing situltahdously; This
would result in glutting the packing houses with much of the acreage hot
being harvested. Genetically controlled maturity dates should reduce the
likelihood of such a disaster.
Another objective specific to the machine-harvest program is to incor-
porate resistance to common diseases other than those listed above. Resis-
tance genes which are being combined with the resistance to gray leafspot,
Verticillium wilt, races 1 and 2 of Fusarium wilt and tolerance to early blight,
gray wall and TMV include resistance to bacterial wilt, bacterial canker,
early blight and leaf-miner.
Other objectives of the tomato breeding program include development of
multiple disease resistant short-stake and trellis grown varieties for this
industry as well as machine-harvest types for the small but significant pro-
cessing tomato industry,
Basic studies are conducted in the areas of a) breeding methods, b) ge-
netics of horticultural characteristics, c) genetics of disease resistance,
d) methods and techniques of screening for disease resistance and e) chemistry
of disease resistance. Information from these studies is then translated into
applied benefits in the breeding program. This departure from the classical
approach to breeding for disease resistance is expected to advance the breeding
and development of resistant crop varieties at a much accelerated pace.
1, Crill, Pat and B. Villalon. 1970. Tomato Variety Development in Florida.
Florida Grower and Rancher, February 1970.
2. Crill, Pat and B. Villalon. 1970. Genetic control of tomato diseases
and pests. Florida Grower and Rancher, May 1970.
3. Schmidling, Joe. 1969. The development of disease resistant tomatoes.
Florida Grower and Rancher, December 1969.
4. Villalon, Ben and P. Crill. 1970. Breeding fresh market tomatoes for
mechanical harvesting. Florida Grower and Rancher, March 1970.
5. Walter, James M. 1967. Hereditary resistance to disease in tomato.
Annual Review of Phytopathology 5:131-162.
6. Weber, George F. 1939. Nailhead spot of tomato caused by Alternaria
tomato. University of Florida, Agricultural Experiment Station
Technical Bulletin 332.
7. Weber, George F., S. Hawkins, and D. G. A. Kelbert. 1932. Gray leafspot,
a new disease of tomato. University of Florida, Agricultural Experiment
Station Bulletin 249.
TABLE I. TOMATO VARIETIES DEVELOPED BY THE
UNIVERSITY OF FLORIDA
CHEMICAL CONTROL MATERIALS AND GENETIC
SERIOUS DISEASES AND PESTS OF TOMATO.
RESISTANCES TO SOME
CHEMICAL GENETIC RESISTANCE
DISEASE OR PEST CONTROL OR TOLERANCE
Nailhead spot Yes Resistance
Early blight Yes Res. & Tol.
Other Alternaria diseases Yes Tolerance
Gray leafspot Yes Resistance
Cladosporium leaf mold Yes Resistance
Fusarium wilt (2 races) Yes Res. & Tol.
Verticillium wilt Yes Res. & Tol.
Botrytis graymold Yes None
Late blight Yes Tolerance
Bacterial leafspot Yes None
Bacterial wilt None Tolerance?
Bacterial canker None Tolerance?
Virus diseases None Res. & Tol.
Leaf miner Yes Resistance?
Aphids Yes None
Lepidopterous larvae Yes None
Nematodes Yes Resistance to some