Vegetable Improvement Newsletter No. 6, February 1964

Compiled by D.H. Wallace, Cornell University, Ithaca, New York

1. Inbreeding and Heterosis in Asparagus

Philip Ito and T.M. Currence

Department of Horticulture, University of Minnesota, St. Paul

Sib crosses were made to develop inbred lines. Ten female plants from each of 9 inbred lines ranging four to eight sib-crossed generations were chosen as maternal parents. Parentage of these inbred lines was quite diverse including the species brachyphyllus and two foreign varieties. Also 2 female and 2 male Washington plants that had proven outstanding in progeny tests occur in the pedigrees. Ten female plants from each of 6 varieties were also included as female parents. These were from commercial seeds. One was designated by the seed company as a commercial hybrid. The only male parent was a plant of a perfect flowering line that came from Holland. It had been selfed three generations.

A test of the 15 crosses and 16 parents in randomized blocks has now been harvested one season. Yield of the nine inbred lines was 55 percent of that of the 6 varieties. Inbred lines ranged from 54 to 695 grams per twelve plant plots and varieties from 588 to 1008. The loss in vigor was at least to some extent recovered in the crosses. All crosses ranged from 80 to 260 percent of their higher yielding parent and 127 to 398% of the averages of both parents. These percentages were definitely higher for inbred line crosses than they were for variety by inbred crosses. Inbreds being low in vigor is an apparent reason. The preliminary results based on only one year's yield data do not show promise for hybrid vigor to improve commercial asparagus. Two of the 9 inbred crosses were approximately equal to the best of the 6 commercial varieties for both average yield and average spear size; but none of them can be considered as definitely superior at this state of testing.

Uniformly large spears with high yielding ability is a type hoped for. Uniformity was evaluated by diameter of stalks taken during the first growing season. Coefficients of variability based on single plant data are a measure of uniformity. Coefficients of variability based on single plant data are a measure of uniformity. Inbred lines should be more uniform and should produce more uniformity in their crosses due to a greater degree of homozygosity. The coefficients of variability however, do not support of this expectation. Some lines were more uniform than others but no relationship to inbreeding is apparent. It seems probable therefore that environment was responsible for much of the variation in stalk diameter. Several other measurements of vigor give approximately the same indications. Tentative conclusions at this time are that inbreeding reduces vigor but vigor is recovered in crosses. Hybrid vigor therefore occurs but so far the tests give no indication that inbred crosses will prove superior either in vigor or uniformity to good open pollinated varieties.

2. Polyploidy in Cucumis sativus L.

J.L. Bowers

University of Arkansas, Fayetteville, Ark.

Seed of a gynoecious cucumber breeding line in the cracked seed coat stage were soaked in 2 per cent colchicine solution for a 4 1/2 hour period. In addition to this procedure for including polyploidy, a group of seedlings growing in total darkness were treated by placing one drop of the .2 per cent colchicine solution on the growing point each day for a period of ten days. Tetraploid plants have been obtained by following both these procedures.

The tetraploid plants of the gynoecious line (Gy 34) have been selfed out twice and the progeny have exhibited very low fertility. The 4x plants were sprayed with gibrelate "400" solution 1500 ppm, at weekly intervals.

The first spray was applied when the first true leaf was half unfurled, and four spray applications were made. Excellent male flower production was obtained, and most flowers produced an abundance of pollen. The pollen grain from tetraploid plants were about 6-8 microns larger in diameter than those from diploid plants. Although we did not have the diploid plants of line Gy 34 from comparison with the tetraploid Gy 34 on the basis of male flower development, it appeared that the gibrelate "400" treated tetraploids developed more male flowers. The non-sprayed tetraploid plants did not develop any male flowers and this has been typical for the diploid form of Gy 34 when it is not sprayed.

Seed production records have been kept for individual plants of the tetraploid group. There does appear to be some variation in seed production between different plants and an effort will be made to select for higher fertility.

3. A Radiation-Induced Seedling Marker Gene for Cucumbers

R.W. Robinson and W. Mishanec

New York State Agricultural Experiment Station, Geneva

A mutant cucumber plant in the R₂ generation following seed treatment with thermal neutrons was first noticed because of the glossy appearance of its foliage. The mutant lacked epidermal hairs on its foliage and spines on its fruit. It appears useful as a seedling marker, since mutant plants are easily classified in the first true leaf stage and have been good vigor and fertility. It is inherited as a monogenic recessive, designated glabrous (gl) and its linked with the yellow cotyledon (yc) gene.

4. Bush Cucurbita moschata

E.M. Meader and Lib Hung

Department of Horticulture, University of New Hampshire, Durham, N.H.

Spring of 1959, seeds of Cucurbita moschata labeled: F₃ bush BX60, and with notes on the packet "Short internodes - very small plant- many pistillate flowers but few corollas open normally - have failed to correct this fault. Bred here. M. Hardin were received from the late Mr. Hardin, Geary, Oklahoma. When some of these seeds were grown in the field at Durham, only normal vines were observed. The last three seeds of Hardin's F₃ bush BX60 were planted in the greenhouse in the spring of 1962 and selfed seeds were saved from one plant after a cooking test had been made of the mature fruits. This plant was not bush and the fruit was not oblate, thick-walled pumpkin rated of good quality.

The selfed seeds of F₃ bush BX60 - 1 in 1963 gave in the filed 31 light-green colored, viney plants and 15 dark-green bush plants. segregation was in a 2:1 ratio. As noted b Hardin, the bush plants produced abnormal flowers. Unusually large ovaries developed below the closed corollas, some being 6 inches long and 2 inches in diameter. When the closed corollas were torn open (they never opened normally) and self-pollinations were made, some large fruits resulted. All proved to be void of seeds. Pollen from the bush plants seemed normal. Some pollen was used to pollinated C. mixta (P. I. 165558). Ample amounts of plump seeds were obtained from this cross.

It is of interest that O.H. Pearson, S.R.S., Hollister, California, who saw the bush plants of C. moschatain the filed at Durham in August, said that he had somewhat similar material at one time but failed to maintain the character. Hardin's bush character in C. moschata has not been lost yet, as it is being carried as a recessive in the remnant (50 seeds) of NH #F₃ bush BX60-1 and in the hybrid with C. mixta. It is doubtful if the parents that gave Hardin's bush character in C. moschata can ever be ascertained. Similar to the bush character in C. maxima late in the growing season the bush C. moschata tends to make longer internodes so that a short vine ( 5 to 6 feet) results.

5. Short Internodes and Raceme Type Baby Lima Beans

R. E Wester and E M. Rahn

U.S. Department of Agriculture, Beltsville, Maryland

A cooperative project between the Delaware Agricultural Experiment Station and the U.S.D.A. was started in 1963 to develop a baby lima bean variety with short internodes and racemes to replace Thaxter with long internodes and racemes. One hundred lines were tested in 1963. Field selections were made from one line that had the above characters. These were grown at Beltsville during 1963-64 winter and will be further tested at Georgetown, Delaware, with other lines that have never been tested. These lines are resistant to downy mildew strains A and B.

Downy mildew strains A a B in 1963 by R. E Wester, John MacLeod, and J.W. Heuberger. Downy mildew strain A was recovered from a number of locations a in Mary land, Delaware, and New Jersey, but strain B was not during the 1963 season.

6. Dark Red Surface Color Character in Tomato

Paul G. Smith

Department of Vegetable Crops, University of California, Davis

A dark red surface color character for ripe fruit has been found in small-fruited cherry type tomato. F₁ plants had essentially the same color as the dark parent, suggesting a single dominant tree. The inheritance will be studied more completely in the summer of 1964.

This character may have value for breeders of market type tomatoes because of the more attractive appearance as compared with normal fruit. The deep red color extends only through the fruit wall and not throughout the fruit.

7. Effect of Hot Weather on Flesh Color of Tomatoes

P.A. Young

Ordinary varieties of tomatoes ripen with prettiest flesh color at temperatures near 60 to 80? F. Temperatures near 90 to 95? F. often result in lighter red and more yellow color. Gulf State Market tomatoes in hot weather commonly showed soft purple-red blossom-ends before the hard green tops turned red, making the fruits unmarketable. Weather often is hot, part of the time in the ripening season of tomatoes, so we need varieties that develop satisfactory red color in hot weather. Flesh color was studied in the tomato variety test in the summer of 1963. The plants were set in a field on June 3rd and ripened fruits in July and August when temperatures often were 90 to 95? F. Rutgers set few fruits in hot weather.

Alpha 88FR tomato produced abundant dark red fruits in the spring crop but the fruits in the summer crop had pale pink and white flesh color; it set abundant fruits in hot weather. In contrast to Alpha 88FR, the new Red Bobs variety from Canada set abundant fruits with bright red flesh color in summer weather. Satisfactory red flesh color also developed in Pinkdeal, Hotset and Early Alberta in hot weather. Thus, resistance to heat sterility is combined with development of bright red flesh color in some varieties already. The problem remains to develop varieties with these virtues plus the large plants and fruits needed for commercial canning purposes.

Common varieties of tomatoes less than entirely ripe usually have white locule walls in the fruits. The sliced tomatoes are attractive with their contrasting red and white colors. We should like them that way. However, better color of canned tomatoes can be attained with fruits that have pink to red cores and locule walls. This can be improved by crosses and selections. High Crimson tomatoes need to become very ripe to develop their superior color, thus being like cannery varieties.

8. Solving Some Problems for Greenhouse Tomatoes

P.A. Young

Experience with greenhouse tomatoes in 1948 to 1964 indicates emphasis on some methods for increasing profits and decreasing losses. Varieties are to be chosen for each area of production. For example, Tuckcross "O" was unsatisfactory for winter production at Jacksonville, Texas because the stems were spindly and the fruits were small. In contrast at Arlington, Texas where there is more sunlight in winter, Tuckcross "O" developed thick stems and large fruits in winter. At Jacksonville, Tuckcross V bore best in winter.

Flower development and fruit setting are apt to be poor when light intensities are less than 1000 foot-candles in daytimes for a week or longer. Such dim light is common in foggy or stormy weather in November to January at Jacksonville, Texas so the tomato plants often stopped blooming then. The Weston Exposure Meter is useful in determining the light intensity (illuminance) in the tomato greenhouse, as the meter reading X4 gives foot-candles. Illuminance of 2000 to 5000 foot-candles facilitates fine growth of the plants. Plans for fertilizing the tomatoes vary with the light available from week to week. Common tomato varieties presumably are influenced little by length of day but are greatly influenced by the total amount of light per day.

Tomato plants for the greenhouse were grown in a mixture of perlite-peat-sand with abundant commercial fertilizer in 5 inch flower pots. The fall weather was hot, dry and windy so the plants were watered abundantly with a garden hose. Soon the plants began to grow poorly and showed leaf symptoms indicating either fertilizer excess or deficiency. A test showed that the mixture in the pots was nearly lacking in fertilizer so it was necessary to fertilize the plants through their leaves to save them. The fertilizer had been leached from the soil in the pots.