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Vegetable Improvement Newsletter No. 10, February 1968
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Compiled by H.M. Munger, Cornell University, Ithaca, New York

1. A Chromosomal Interchange in Cabbage

M.E. Nasrallah

Biology Department, State University College, Cortland, N.Y.

A naturally occurring case of semi-sterility was observed in one plant of a self-fertile line derived from the Cornell release 52-153. The semi-sterility was manifested in reduced seed set. Microscopic examination of the pollen of this plant revealed that approximately half of the grains were aborted and did not stain with acetocarmine. The chromosomes were subsequently examined by the "acetocarmine squash method." This revealed the presence of seven pairs of bivalents and a ring of four chromosomes at Metaphase I of meiosis. The association of four chromosomes at Metaphase I was considered evidence that the plant was a translocation heterozygote. Approximately half of the progenies of this translocation heterozygote (T/N) had normal pollen (all stainable with acetocarmine), the other half had 50% abortive pollen. Such a ratio fits the expectation since selfing of a T/N plant yields 1 N/N : 2 N/T : 1 T/T progenies. The N/N and the T/T have 100% fertile pollen.

Seed of the translocation heterozygote is available and might be of interest to those who are engaged in linkage studies.

2. Downy Mildew Resistance in Certain Brassicae

W.C. Barnes and W.R. Sitterley

Clemson University Truck Experiment Station, Charleston, S.C.

Resistance to downy mildew in cabbage was obtained by crossing with two French cabbages, PI 261774 and 267769. The latter was a semi-savoy type and transferred so little fiber to the progeny it was discarded from the program. Very good resistance in the heading stage has been observed in fall and spring crops both of which mature when climatic conditions are favorable for the pathogen. The spring crop plant beds are seeded Oct. 1-15 thereby making them in the juvenile stage when the fall crop is heading. In the plant bed resistant plants show some tolerance to the pathogen but the degree of injury is in great contrast to the high degree of resistance in the heading stage.

This same resistance was incorporated into collards by crossing with the PI 261774 cabbage and the juvenile stages of this crop respond in a similar manner.

Resistance in broccoli was obtained from PI 189028. This crop is planted in August when temperatures are too high for the pathogen to be active. Normally the plants are old enough to be quite resistant by the time the pathogen becomes active. Although no real test has been conducted on juvenile broccoli there are indications it responds in somewhat the same manner as cabbage.

These observations lead us to conclude that downy mildew resistance in these brassicae is definitely influenced by age of host plant with the juvenile stage being the least resistant. A puzzling spot frequently found on the tops of maturing resistant heads and once thought to be caused by downy mildew has been proven to be either a virus or more likely a non pathogenic lesion caused by something like ozone.

3. Observations Made on the Sex Expression of F-1 Hybrids Developed By the Use of the Gynoecious Character

J.L. Bowers

Department of Horticulture, University of Arkansas, Fayetteville, Arkansas

Prior to the summer of 1966, the F-1 hybrid plants developed through the use of the gynoecious character appeared to be strongly gynoecious in the plantings at Fayetteville, Hope and Bald Knob. Some small amount of classifying plants on the basis of sex expression has been carried out but as a general rule most of the plants had been classified as gynoecious or partly gynoecious except where two way crosses had been made. Plants of the two way cross generally had 40 to 60 percent of the plants classified as monoecious in contrast to the very low percentage (0-5 percent) of monoecious types found in F-1 hybrids.

The inspection of the Bald Knob planting in June, 1966, led the staff to give consideration to the classifying individual plants on the basis of sex expression.

The six commercial F-1 hybrids in this trial had a fairly large number of plants classified as monoecious, ranging from 27.1 to 49.2 percent. The station's two way cross in this same trial had 58.5 percent of its plants classified as monoecious. In 1967 plants of seven F-1 commercial hybrids were classified on the basis of sex expression in the Bald Knob trial. Only one of these seven hybrids had been evaluated on this basis in the 1966 trial. The percentage of plants classified as monoecious among this group of hybrids ranged from 7.9 to 47.2. There were three hybrids showing less than 15 percent monoecious types and four hybrids that had 28.8 percent or higher of its plants classified as monoecious.

The data on sex expression of plantings of hybrids at Hope, Arkansas leads the staff to consider toe effect of plant crowding on sex expression. In replications 1,2, and 3 of the Pioneer F-1 hybrid in the variety trial, gave this percentage of monoecious types: 10.0, 22.2, and 0, respectively. Plants of the fourth replication where the hills were not thinned and contained as many as 4-5 plants per hill were all classified as monoecious. The crowding or shading effect may be responsible for this high production of male flowers and might point to light intensity as a factor influencing sex expression as shown by E. Kooistra (1) in the Netherlands.

(1) E. Kooistra. 1967. Femaleness in Breeding Glasshouse Cucumbers. Euphytica Vol. 16: 1-17.

4. A Rapid Test For Scab Resistance in Cucumber

H.M. Hunger and R.E. Wilkinson

Cornell University, Ithaca, N.Y.

In conventional testing for scab resistance, cucumber seedlings are grown in flats, inoculated by spraying with a spore suspension when cotyledons are fully expanded, and kept in a moist chamber at 65-70? for 5-7 days. It usually takes nearly 3 weeks to complete such a test, and it is difficult to test more than 50 seedlings in a 12x16 inch greenhouse flat.

We have found that seedlings germinated in paper towels can be used for a quicker test and one that requires only a small fraction as much space as the conventional method. A doubled paper towel (5" x 10") is moistened and seeds are placed in a row, hilum down, about 1/2 inch from the top along the 10 inch edge. Another moistened paper towel is placed over the first to hold the seeds in place, and a pot label inserted for identification. The towel is then rolled loosely and placed upright in a container about 5 inches deep with a trace of water in the bottom. If held at approximately 90? F, most seed lots germinate and develop hypocotyls about an inch long in 3 days. At this time they are ready for inoculation, which is done by exposing the entire seedlings and spraying them with spore suspension of the scab-inciting organism, Cladosporium cucumerinum.

The towels are then re-rolled and placed in their container in a moist chamber held at 65-70? F. Readings can usually be made on the fourth day following inoculation, although the differences may be sharper on the fifth day. Hypocotyls of susceptible seedlings become gray, soft, and watersoaked in appearance while resistant seedlings remain greenish white and turgid.

Resistant seedlings can be transferred to flats or pots without any problem of survival. There appears to be some superficial mycelial growth on the cotyledons of resistant seedlings while in the moist chamber, but this disappears quickly after transplanting.

In addition to the saving of space and time, this technique has two other advantages. (1) It eliminates damping-off which sometimes causes problems when seedlings growing in soil are held under cool, moist conditions for several days. (2) Counts of resistant susceptible seedlings can be made considerably faster and more accurately where each lot consists of small seedlings exposed on a separate towel than where they are growing in flats.

5. Gibberellin A4-A7 for Staminate Flower Induction on Gynoecious Cucumbers

L.M. Pike and C.E. Peterson

Michigan State University, East Lansing, Michigan

A new formulation of gibberellin (A4A7)1 was compared with potassium gibberellate (KGA) on gynoecious cucumber line MSU35G in greenhouse and field trials in 1967. The latter formulation was selected on the basis of a 1966 field experiment in which KGA at 1000 ppm produced satisfactory induction compared with virtually no response from butoxyethyl gibberellate.

Extreme vegetative response, observed in the greenhouse plants treated with A4A7 at concentrations of 100 ppm or more, indicated clearly that such plants could not withstand the rigors of the outdoor environment. Since the minimum (100 ppm) concentration used in the greenhouse was found to cause injury, our field treatments were at concentrations 25, 50 and 100 ppm of the A4A7 and 250, 500 and 1000 ppm of KGA with one, two and three applications of each dilution.

Satisfactory induction was secured in the field with three applications of 25 ppm of A4A7 beginning when the first true leaf had expanded to 1 inch diameter with the second and third applications at 4 day intervals. At 50 ppm induction with A4A7 was significantly better than with 1000 ppm of KGA. Excessive vegetative response and some damage resulted from 100 ppm of A4A7 .

From our experience with this material we have concluded that the total quantity of gibberellin absorbed per unit of plant weight or volume is more important than the dilution at which it is applied. It is easy to get an overdose on small plants even at low concentrations, if the plants are treated too frequently or if normal growth is checked by environmental stress. If plants have not produced new leaves or if excessive damage from previous treatments is evident, additional applications should be delayed until plants show normal growth. Severe damage and high mortality have been observed with both KGA at 1000 ppm and A4A7 at 50 ppm under conditions of extreme heat and drying winds. Until precise procedures are worked out for A4A7, it is suggested that one-half of the plants to be treated should receive 25 ppm and the other half 50 ppm when the first true leaf is expanded to about one inch. The two or three subsequent applications at 50 ppm may be at approximately weekly intervals depending upon growth of plants and severity of vegetative response from preceding treatments.

We have good results with a volume of approximately 2 ml per plant applied to the growing point and 1 or 2 expanded terminal leaves each time the plants are treated. On rapidly-growing seedling plants in the greenhouse, good induction with no injury has been secured following a schedule of 3 treatments at 4-5 day intervals using A4A7 at a dilution of 25 ppm and an approximate volume of 2 ml per application directed to growing tip and the last expanded leaf.

1 Supplied by AMDAL Company, Division of Abbott Laboratories, North Chicago, Illinois.

6. Cucumber Beetle-Resistant Cucurbits

O.L. Chambliss

U.S. Vegetable Breeding Laboratory, Crops Research Division, Charleston, S.C.

F.P. Cuthbert

Vegetable Insects Investigations, Entomology Research Division, Charleston, S.C.

We have found a number of commercially available varieties and plant introduction of squash, muskmelon, and watermelon (cucumbers were omitted in this test to be highly resistant to the banded cucumber beetle ( Diabrotica balteata). Preliminary observations and reports in the literature indicate that they may be resistant to the spotted (D. undecimpunctata howardi) and striped (Acalymma vittatum) cucumber beetles as well. Our screening technique consisted of planting seeds in flats of soil in a greenhouse section where they were continually exposed to a high population of insects while germinating and emerging. using mass-reared insects in numbers greatly exceeding the natural population allowed us to apply considerable selection pressure and obtain a high level of resistance.

The following list of cucumber beetle-resistant varieties and plant introductions maybe useful to breeders interested in including resistance as part of their breeding program:

Cucurbita maxima is the only major species in which we did not find a varietal source of resistance, although we did find 3 resistant PI's in that species.

Although resistance is commonplace in Cucumis melon, a number of varieties were highly susceptible; Honey Dew, Honey Dew Baby Slip, Persian (medium), Casaba (Sungold, Cranshaw, Golden Beauty), Smith's Perfect, Florida Honey Dew #1, and Florida (4-4).

Watermelons are reputed to suffer the most damage from cucumber beetles of any cucurbit species. To our knowledge no previous report of the resistance of Sugar Loaf has been made. It has a much higher degree of resistance than any of the varieties we tested that are reported to have a degree of resistance.

7. A Chlorophyll-Deficient Mutant in Lettuce

T.W. Whitaker

Crops Research Division, Agriculture Research Service, U.S. Department of Agriculture, la Jolla, California

Several chlorophyll-deficient mutants have been described in lettuce, most of them were cytoplasmic in origin and maternally inherited (Whitaker, Jour. Hered. 5:317-320, 1944). Ryder (Proc. Amer. Soc. Hort. Sci. 86:457-461, 1965) has found a single mutant Cut leaf in irradiated material. this mutant has light green cotyledons and light green leaves, but later the leaves and cotyledons become normal green.

During routine progeny tests for resistance to lettuce downy mildew ( Bremia lactucae), we found a progeny (segregating for resistance which had several seedlings with light green cotyledons. Leaves of these seedlings develop some dark green pigment, but they also develop large white areas apparently without chlorophyll. Nearly all of the mature leaves of the mutant have these large patches devoid of pigment, which give the plants an odd, calico appearance. The distinctive light green cotyledons make this mutant easy to score in the seedling stage. The chlorophyll-deficient plants produce a modest amount of seed, although the quantity is greatly reduced compared to normal green plants (6.42 g vs. 29.71 g per plant).

This progeny (52435) in the 7th generation of selection, was derived from crosses involving Imp. 615, Climax, and a downy mildew resistant line. Our tests indicate that this chlorophyll-deficient condition is dependent upon a single recessive gene for expression.

A comparative analysis of the quantity and quality of chlorophyll from deficient plants and their normal green siblings indicates that the deficient plant have only 13 percent as much total chlorophyll as normal green plants. The ratio of chlorophyll as to chlorophyll b, however, is the same in both mutant and normal green plants.

This chlorophyll-deficient mutant should be of value in linkage studies. Small samples of seed of this mutant are available to lettuce breeders, and can be obtained from the U.S. Horticultural Field Station, La Jolla, California 92037. the chlorophyll determinations were made through the courtesy of Professor F.T. Haxo, Scripps Institution of Oceanography, University of California, San Diego Campus.

8. Pseudo-cleistogamy in the Muskmelon Cucumis Melo L.

G.W. Bohn

Crops Research Division, Agriculture Research Service, U.S. Department of Agriculture, la Jolla, California

Renewed interest in Enzie's (ASHS 43:195. 1943) cucumber mosaic resistant "Oriental Pickling Melon" stems from its resistance to races 1 and 2 of Fusarium oxysporum f. melonis (Leach & Curr) Sn. & H., reported by Risser and Mas (Ann. Amelior. Plantes 15:405. 1965). Accordingly, seeds derived from the naturally pollinated L.J. 17187 ( = Risser and Mas' CM 17187) and of its strictly inbred sib, L.J. 34205, were grown in the greenhouses at La Jolla for seed increase by bulk crossing S2 and S3 sib lines.

Flowers were not tied to prevent corolla expansion because: (1) bees rarely penetrated the screened greenhouses and (2) pistillate (perfect) flower buds were emasculated and pollinated the day before anthesis. Pistillate flowers left untreated usually dropped. Natural setting of fruits from untreated flowers usually indicated imperfect exclusion of bees.

Surprisingly, S3 progenies L.J. 35188 and 35190, from "Enzie's Conomon" plant 10, and O.S. progenies L.J. 90321 and 90322, from "Enzie Conomon" plant 1, set fruits repeatedly from untreated flowers. Such fruits competed successfully with fruits set from sib-line pollinations. They were about as large as hand-pollinated fruits at maturity; and they contained some plump seeds. Subsequent observations supported the belief that these plants set fruits in the absence of honeybees or other pollinators.

The hypothesis was tested on a small scale by tying corollas of 5 flowers on 2 plants of L.J. 17187 inbreds and 10 flowers on 3 plants of L.J. 34205 inbreds. Fruits set from hand pollinated flowers and from untreated flowers on those plants and their sibs served as controls.

Despite their derivation from sibs that appeared nearly alike in the 1947 planting, the 2 populations yielded different results. Fruits set from flowers of 17187 inbreds that were tied the day before anthesis and left undisturbed until harvest contained as many plump-seeds as did fruits from selfed, cross-pollinated, or undisturbed flowers (Table1). Tied flowers of 34205 inbreds set fruits readily, but the fruits contained no plump seeds. Instead, they contained apparently empty "seed coats" nearly as large as plump seeds.

These observations suggest that the population derived from 17187 was pseudocleistogamous and self-fertile; while the related population derived from 34205 was either parthenocarpic or pseudocleistogamous and self-sterile. The enlargement of 34205 plants set seedy fruits from self-pollinated flowers, so they were obviously self-fertile. The fruits were thus parthenocarpic.

Additional study will be required to determine the mechanism operating to yield seedless and seeded fruits from open and tied flowers of these populations. Parthenocarpy is well known in Cucumis sativus L. and it has been observed in other cucurbits. however, I know of no reports of cleistogamy or pseudo-cleistogamy in the Cucurbitaceae.

Table 1. Average number of plump seeds in Enzie's C. melo var. conomon fruits set from flowers treated in different ways. La Jolla, California. 1967.

Treatment
Self
Sib
Cross
Tied, not pollinated
Population
Sample size
No. seeds
Sample size
No. seeds
Sample size
No. seeds
Sample size
No. seeds
Sample size
No. seeds
17187
3
50
29
200
7
109
4
57
3
93
34205
6
175
13
99
3
36
2
9
7
0

9. A Red Stem Pigment Muskmelon

G.W. Bohn

Crops Research Division, Agriculture Research Service, U.S. Department of Agriculture, la Jolla, California

We observed a red pigment in the stems of Cucumis melo L. P.I. 157083 seedlings grown in the greenhouse at La Jolla in 1961. The pigment first showed in vascular traces to cotyledons in hypocotyls of 30-day-old plants. Subsequently, red pigment developed in irregular patches just under the epidermis of stems, especially at nodes. The pigment did not persist in one location; it developed in young-maturing stem tissues below the elongation region, and usually disappeared as the section of stem aged. The pigment was not observed in field-grown plants. So far as we are aware, this is the first record of a red pigment in stem or leaf tissue of any cucurbit. K.S. Chester quoted N.I. Vavilov, in Chronica Botanica 13:1/6, 1951: "Despite an extended search among thousands of varieties of watermelon, muskmelon, squash, and gourds, we have not once found forms with anthocyanin in the stems or roots."

The red-stemmed introduction, a small-fruited feral or semi-feral muskmelon collected by H.L. Crane in Lanchow, China, was crossed with a standard green-stemmed cantaloupe. Two small F2 progenies, totaling 94 plants, segregated 68 green- and 26 red-stemmed plants. Thus the red stem character was dependent on a single, recessive gene (Chi square, 0.35). The gene for red stem is symbolized r. The population was segregating, also, for resistance to powdery mildew, Pm2, from the green-stemmed parent (Bohn and Whitaker, Phytopath. 54:587. 1964). The coupling phase dihybrid classes in F2 were 56 Pm2R: 20 Pm2r: 12 pm2R: 6 pm2r. The numbers approximated those expected with independent assortment (Linkage Chi square, 0.48).

Dr. Randolph Wedding, University of California at Riverside, observed that the pigment was located in the walls of thick-walled cells, probably bast fibers. Such cells formed the outer layer of vascular bundles and occurred as islands within the bundles. The pigment disappeared in acid, neutral, or alkaline alcohol. Dr. Wedding stated that the pigment was not an anthocyanin, because it was not located in the cell vacuole, and it was not directly soluble in (but reacted with) alcohol.

Subsequently, Dr. F.P. Zscheille, Jr., of the University of California at Davis, confirmed Dr. Wedding's observations. He found the pigment soluble in water and in acetone. From absorption spectra of acetone-hexane extracted material, Dr. Zscheile concluded that the pigment was not a carotenoid.

From its occurrence in thick-walled cells in young-maturing stems and its disappearance in aged stems, Dr. T.A. Geissman, of the University of California at Los Angeles, suggested that the red pigment may be a precursor to lignin.

Red stem is easily scored in greenhouse cultures, and serves as a genetic marker for seedlings in linkage studies. Linkage studies with other seedling and young plant markers are in progress.

Small samples of seed are available from the U.S. Horticultural Field Station, La Jolla, California 92037.

10. A White Flower Cantaloupe

C.F. Andrus

U.S. Vegetable Breeding Laboratory, Charleston, S.C.

This mutant appeared first in April 1967 in a greenhouse planting of 7 selfed lines from a selfed parent line, which was a culmination of 15 generations of mixed mass selection in isolation and enforced sib-crossing. Three of the 7 selfed sister lines segregated a portion of seedlings having a Chlorina pattern of mixed yellow and green. The yellow-green segregants from the populations were bulked to form the foundation stock (C879) which is offered to other breeders for experimental use.

The first generation of C879 in the field had vine vigor comparable to the normal green sister lines. All C879 plants developed flowers with off-white or very pale green petals and bright orange stigmatic surfaces. Few fruit were set on these vines, either by hand or by open pollination. This greenhouse crop revealed that effects of the color mutation extended also to the stems, which had a notably pale green color.

Flowers again were near white and slightly reduced in size in comparison with the normal sister lines. There seemed to be no scarcity of pollen or of pollen vitality. The percentage of fruit set by hand-pollination was about equal to that on normal plants. However, after the initial flowering period the greenhouse grown plants went into a phase during which no flowers developed. No explanation for this occurs to us at the moment.

We have completed no genetic studies on this mutant, nor have we determined the full range of its pleiotropic effects. A few seed are available to cooperators who wish to make further studies. The stock (C879) has the potential of a useful genetic marker which can be detected in the seedling stage and in all subsequent stages of plant and fruit development. A study of light requirements could lead to improvement of seedling survival and of flower development.

Other yellow-green mutants are known in Cucumis melo, but none that are associated with white flower and yellow flesh.

11. A Male-Sterile Pea Line

D.R. Bienz

Ziraat Fakultesi, Ege Universitesi, Bornova, Izmir, Turkey

During the summer of 1965 two individual plant selection lines of the G113 pea cultivar contained plants which failed to produce pods. Examination showed that flowers of these plants were normal except that the anthers contained only shriveled pollen. No normal pollen grains were seen in any anthers examined microscopically. The male-sterile plants remained green long after other plants of this line had matured and turned yellow.

Several crosses were made by pollinating sterile plants with pollen from neighboring plants from the same line. Almost all produced pods with as much seed as is usually obtained when normal plants are emasculated and artificially crossed. It was hoped that at least one of the pollen parents might be heterozygous for male-sterility, but the F1 plants grown in the greenhouse during the winter of 1965-66 were all normal.

A small planting of F3 seed grown in the greenhouse during the winter of 1966-67 produced 6 male-sterile and 27 normal plants. As was true in the field planting, the only abnormality of the sterile plants was shriveled pollen.

12. 'Sweet Goldilocks' Sweet Corn

W.H. Lachman

Department of Plant and Soil Sciences, University of Massachusetts, Amherst, Massachusetts

'Sweet Goldilocks', a yellow hybrid sweet corn, has been tested in our experimental plots for the past three years. It appears to have merit as an especially fine quality variety and suited for growing in the home garden or for selling at the roadside stand. Its medium sized ears are very attractive and mature two to three days before those of 'Tastyvee' and 'Butter and Sugar'. The twelve-rowed ears from 'Sweet Goldilocks' are slightly smaller than from the varieties mentioned previously but produce more ears per plant and out-yield them by an average of 8.6 and 21.0 per cent in total weight respectively.

The outstanding feature of this new hybrid is the extreme tenderness of its pericarp, its excellent flavor; the kernels tend to remain at peak quality a significantly longer period than with most other varieties of current importance.

The pedigree released here for the first time is as follows:

Seed parent - Ma 21547-1-P

Pollinator - Vineland 576

The parent lines are of similar maturity range and it appears that pollination will be complete in the seed production field when they are planted simultaneously.

Seed has not been produced in quantity but a limited number of trial samples are available upon request.

(Research has been supported by NE-32 Regional funds.)

13. An Effective and Efficient Method for Making Artificial Cross-Pollinations of Tomato

F.F. Angell and M.L. Robbins

Department of Horticulture, University of Maryland

The main steps in making artificial cross-pollinations of tomato are emasculating seed parent flower, pollen collection, and pollen application. The present methods for performing the latter two steps are tedious and often wasteful of scarce pollen. Presented in this note is a description of an improved method for collecting and applying tomato pollen.

Pollen is collected directly into No. 4 gelatin capsules. The anther cone of open flower is partly inserted into the small section of a capsule and the flower is then vibrated. The two sections of a capsule are then brought together to provide a closed container. The capsules containing pollen are placed into small holes in a piece of styrofoam. The styrofoam serves as a convenient container for storing capsules in refrigeration and while making pollinations in the greenhouse or field.

Gelatin capsules will soften and collapse if they come in contact with moisture so efforts must be made to keep them dry at all times. We have lost very few capsules because of this moisture problem. Glass vials would be superior to gelatin capsules; however, we have not been able to find vials of suitable size.

Pollen is applied by carefully dipping the stigma of an emasculated flower into pollen in a capsule. The stigma is gently shaken to remove excess pollen before it is withdrawn from the capsule. The stigma is gently shaken to remove excess pollen before it is withdrawn from the capsule. Pollen from one or two flowers is usually sufficient for many pollinations. Pollen in capsules is stored under refrigeration to maintain viability during the interval between pollinations. The length of time pollen will remain viable under those storage conditions has not been determined. Successful results have been obtained with pollen stored 21 days. Generally, the pollen is used within a 10-14 day period.

The method of collecting and applying pollen described in this note has been used successfully in the breeding and genetics program at Maryland. The main advantages of this method as compared with conventional methods are as follows: faster, less time required per pollination; less tedious for individual making pollinations; less chance for contamination during pollination process; conserves pollen, small amount of pollen will pollinate many flowers; effective, generally the percentage of fruit set is increased.

14. Defuzzed Tomato Seed

Carl H. Cadregari

Joseph Harris Company, Inc., Moreton Farm, Rochester, N.Y. 14624

The Joseph Harris Company will make available to research workers interested in direct field and flat seeding of tomatoes, suitable quantities of defuzzed New Yorker and Fireball VR.

Please address inquiries to the author.

15. A Single Gene With Several Desirable Effects for Mechanical Harvesting of Tomatoes

R.W. Robinson and Henryk Wilczynski

New York State Agricultural Experiment Station, Geneva, N.Y.

None of the tomato varieties included in mechanical harvesting tests at Geneva, New York last season was entirely satisfactory. Varieties used for mechanical harvesting in California were too late and susceptible to cracking, while varieties adapted to New York growing conditions dropped their fruit too easily. Breeding lines with the best resistance to "shattering" (premature fruit drop) were those having a jointless gene, such as Jointless Fireball which was developed by H.M. Munger by a backcross program with j-1.

Jointless lines included in this test, however, had poor concentration of maturity. Thus, Geneva breeding line 903 attracted attention because it had good concentration of maturity as well as resistance to shattering. Line 903 is not jointless but has an abscission layer of the type tomato breeders are calling "arthritic joint", which increases the force required to separate the fruit from the vine at the joint.

Line 903 has less apical dominance than normal. Consequently many lateral branches develop rapidly and uniformly, resulting in a compact, bushy plant with many fruit ripe at the same time.

Inheritance studies with line 903 are underway now, and it is evident that the "arthritic joint" and "profuse branching" characters are associated in segregating generations. Preliminary results indicate that both characters are governed by the same incompletely dominant gene. Further research is in progress to provide more definitive inheritance data, test for allelism at previously established loci, and investigate the influence of this gene on auxin physiology.

Line 903 is under consideration for possible release later this year, and seed is available for trials. It is also being offered to make tomato breeders as parental material since it appears promising that it has a single gene providing several desirable traits, including compact plant habit with good foliage cover, resistance to shattering, concentrated maturity, and a high proportion of stem-free fruit when harvested mechanically.

16. Release of Maritimer Tomato

R.W. Robinson

New York State Agricultural Experiment Station, Geneva, N.Y.

Maritimer is closely related and similar to New Yorker, but differs in a single recessive gene for apple-green immature fruit color. Fruit is larger but later and more susceptible to cracking than New Yorker. It is resistant to Verticillium wilt and late blight (race 0). The darker green fruit of Maritimer has proven advantageous to growers in the Maritimes who process green tomatoes, but Maritimer appears less suitable for fresh market and processing of ripe fruit than New Yorker.

17. Observations on Low Temperature Fruit and Seed Set in Tomatoes

Paul G. Smith and Archie H. Millett

Department of Vegetable Crops, University of California, Davis

In the Northeastern Regional Plant Introduction Station's annual report for 1967 (dated December 14, 1967), a tomato from the USSR, PI 280597, was reported to be capable of shedding pollen at 50?F. We wish to confirm this and to add a few observations on low temperature setting.

During the spring of 1967, four plants each of a number of tomato varieties and breeding lines were planted in 4-gallon containers and grown to first flowering in a greenhouse. All flower buds were then removed and the plants placed in an air-conditioned greenhouse with the temperature set at 45?F for 14 hours during the night and at 68?F for 10 hours during the daylight. Flowers as they developed were vibrated daily to ensure pollination. The plants were kept in the greenhouse from March 15 to May 5, when they were removed to a regular greenhouse to allow more rapid fruit development. On June 9 all fruit were removed, cut crosswise, and the seed set estimated, using a three-class scale: 5 = good; 3 = fair; and 1 = very few or no seeds. No statistical analysis was attempted. The results, omitting University of California breeding lines, are noted below.

Variety
No. fruits sampled
Seed index
Av. No. fruits/plant
PI 280597
175
3.9
44
Porter
124
3.8
31
New Yorker
89
3.3
22
Summer Sunrise
66
3.1
16
Earlypak #7
29
2.8
7
New Atom
282
1.7
70
Earlinorth
205
1.6
51

It is clear that fruit set and seed set are not necessarily related and that fruit set alone is not a safe criterion for low temperature setting ability. Seed set should be measured as well as the ability to set fruit. Pollen production was not measured, although stainable pollen was produced by all varieties. In agreement with the observation on PI 280597 noted above, this line produced pollen freely, whereas pollen production was fair to poor with the remaining varieties. That PI 280597 not only produced pollen freely, but also had a good set of fruit with seeds, should make it valuable in the development of low-temperature setting varieties.

Some variations in plant growth were evident. All grew slowly and were pale green, with some purpling. Two breeding lines had begun to die by the time the plants were removed. Several lines, near the end of the cold treatment, began to produce small flower clusters from the dorsal surface of the midribs of the older leaves.

Studies are now under way to measure pollen production more precisely in several varieties, including PI 280597, and to observe the morphological changes that occur with the development of the anthers and the release of pollen under these temperatures.

18. Uncatalogued Vegetable Varieties Available for Trial in 1968

This list is aimed at facilitating the exchange of information about potential new varieties, or new varieties which have not yet appeared in catalogues. Persons conducting vegetable variety trials who wish seed of items on this list should request samples from the sources indicated.

It is the responsibility of the person sending out seed to specify that it is for trial only, or any other restriction he may want to place on its use.

Crops are listed alphabetically. For each entry the following information is given: Designation, source of trial samples, outstanding characteristics, variety suggested for comparison (not given separately if mentioned in description), status of variety (preliminary trial, advanced trial, to be released, or released) and contributor of information if different from source of trial samples. Where several samples are listed consecutively from on source, the address is given only for the first.

19. The Glabrous male Sterile Gene in Watermelon

Victor M. Watts

University of Arkansas, Fayetteville, Arkansas

The glabrous male sterile character controlled by this gene is described in the papers listed below. Currently no line carrying msg has been fixed for satisfactory seed yields combined with acceptable horticultural characters for use as an F1 parent.

These stocks are offered to anyone who is interested in exploring their potential.

Literature

  1. Watts, V.M. 1962. A marked male-sterile mutant in watermelon. Proc. Amer. Soc. Hort. Sci. 81:498-505.
  2. Watts. V.M. 1967. Development of disease resistance and seed production in watermelon stocks carrying the msg gene. Proc. Amer. Soc. Hort. Sci. 91: 579-583.

20. List of Members

February 1968

Libraries