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ARS Home » Southeast Area » Charleston, South Carolina » Vegetable Research » Docs » CGC » Vegetable Improvement Newsletter No. 18, February 1976
Vegetable Improvement Newsletter No. 18, February 1976
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Compiled by H.M. Munger, Cornell University, Ithaca, New York

1. Transferring Powdery Mildew Resistance in Cucumber

H.M. Munger

Cornell University, Ithaca, N.Y.

There are several published reports on the inheritance of powdery mildew resistance in cucumber in which several genes, mostly recessive, have been identified. It has not been clear as to how readily a high level of mildew resistance can be transferred to a good horticultural variety that needs it. Therefore, our procedure in making such a transfer to 'Marketmore' may be of interest. Spartan Salad (MSU C7-63) was used as the source of resistance because it has more resistance than most plant introductions, showing no mildew in the field at Ithaca, and in the greenhouse in winter only a slight growth of mycelium on the older leaves and little or no sporulation.

Five backcrosses have been made following the initial cross of Spartan Salad x Marketmore, with Marketmore 70 used in the last 3 backcrosses and selfed after each cross. In each of the resulting segregating generations from 300 to 500 plants were grown at 2 x 2 inch spacing in flats in the greenhouse and inoculated by blowing spores over them as soon as cotyledons were well expanded. Susceptible and partially resistant plants were gradually eliminated and 5 to 10 of the most resistant plants finally selected for making the next backcross.

The highly resistant plant selfed in the F2 generation after the 5th backcross gave rise to uniformly resistant progenies, with a level of resistance essentially the same as that of Spartan Salad. Their yield, maturity, type, and mosaic and scab resistance all seem equivalent to Marketmore 70. Although this material has not been officially named and released, it will probably be named Marketmore 76.

No selection was done for downy mildew resistance at any time in the program, but it was reported from a trial in Mexico that there seemed to be resistance to downy mildew in this material. A greenhouse test in the fall of 1975 at Ithaca confirmed that Marketmore 76 is resistant to both mildews with DMR about the same as in Poinsett.

2. Breeding Snap Beans for Root Knot Nematode Resistance - A Status Report

Jim E. Wyatt, George Fassuliotis and John A. Wells

Agricultural Research Service, USDA, Charleston, South Carolina

A trial of advanced snap bean lines derived from crosses with PI 165426 was planted in a root-knot infested field at Tifton, Georgia. The predominant species of root-knot nematode present was Meloidogyne incognita. Roots were indexed 53 days after planting for root galling and egg masses. Nematode reproduction was estimated by measuring eggs/gram of root.

Two breeding lines were fully susceptible, one line was intermediate and six lines were resistant as determined by both root galling and egg mass indices. Both indices proved equally effective in estimating plant reaction, and the correlation coefficient between the two was r = 0.98. Egg counts were inconclusive as a measure of nematode reproduction.

Near isogenic lines differing in reaction to M. incognita have been established by identifying resistant and susceptible plants. We will continue our studies of these lines to determine the chemical nature of resistance, with a particular interest in chlorogenic acid. We also anticipate publicly releasing the resistant lines after further testing.

3. Root Rot Resistance in Snap Beans

J.E. Wyatt and P.D. Dukes

Agricultural Research Service, USDA, Charleston, South Carolina

Snap bean breeding plots planted here in August, 1975, were subjected to high temperatures and excessive rainfall. These conditions promoted the development of at least four seed and root rotting organisms that caused severe losses in many plots and provided an opportunity to effectively select for root rot resistance.

The planting consisted of both colored- and white-seeded lines with colored-seeded phenotypes comprising about 55 percent of the planting. Seedling survival 17 days after planting was 23% for colored-seeded lines and 14% for white-seeded. This data supports earlier work at this location indicating that root rot resistance in snap beans was correlated with pigmented seed coats.

4. Cercospora Leaf Spot of Southern Pea

R.L. Fery, P.D. Dukes, and F.P. Cuthbert, Jr.

U.S. Vegetable Laboratory, ARS, USDA, Charleston, S.C. 29407

We have had severe epiphytotics of a leaf spot incited by Cercospora cruenta Sacc. in all our fall southern pea planting since 1972. Although already recognized as a major foliage disease in several important production areas of the U.S., we feel that Cercospora leaf spot (CLS) may be responsible for far greater losses than realized at present. Preliminary analysis of data collected this past fall indicates that CLS reduced yields by almost 36%. Results of field tests run over a four year period have confirmed the presence of high levels of resistance in several accessions.

The inheritance of resistance in the breeding lines CR 17-1-34 and Ala. 963.8 was studied in parental, F1, F2, and backcross generations after crossing with susceptible cultivars. We found that the resistance in these two lines were conditioned by different genetic factors. Resistance in CR 17-1-34 was controlled by a single dominant gene and in Ala. 963.8 by a single recessive gene. The dominant and recessive genes have been designated Cls1 and cls2, respectively. Since both of these genes are already in improved type genetic backgrounds, the germplasm is now available to allow the immediate expansion of the objectives of the southern pea breeding programs to include CLS resistance. The breeding line CR 17-1-34 has been released for use in such programs.

5. Breeding Cowpea Curculio Resistant Southernpeas

R.L. Fery and F.P. Cuthbert, Jr.

U.S. Vegetable Laboratory, ARS, USDA, Charleston, S.C. 29407

Three cowpea curculio resistant southernpea breeding lines, CR 17-1-13, CR 18-13-1, and CR 22-2-21, were released to plant breeders this past spring. All are horticultural types suitable for immediate use in breeding programs. CR 17-1-13 has a pod factor that inhibits pod wall penetration by the adult curculio. CR 18-13-1 and CR 22-2-21 both have a nonpreference type resistance. Results of field tests conducted the past two years indicate these lines are as effective as the recommended insecticide in controlling the cowpea curculio. Our studies indicate that the pod factor and the nonpreference factor are complementary in effect. The pod factor is moderately heritable and controlled by a single effective factor. The inheritance of the nonpreference factor is currently under study.

6. Development of Isolation Cages for Controlled Spinach Pollination

D.W. Fankhauser, J.L. Bowers, M.J. Goode

University of Arkansas, Fayetteville, Arkansas

Early in the spinach breeding program at the University of Arkansas attempts were made to devise economical isolation cages to facilitate controlled pollination. Various types of muslin cloth or plastic covered frames failed in the field and greenhouse because environmental factors could not be controlled. We finally developed fairly economical chambers in a greenhouse environment with enabled us to operate the spinach breeding program year round. At Fayetteville, the yearly minimum and maximum temperatures ranged from -5 degrees to 105 degrees Fahrenheit. In order to maintain the desired range of 55 to 70 degrees in the chambers, a system capable of delivering outside air cooled as much as 35 degrees or warmed as much as 60 degrees was required.

Three seed crops have been successfully produced in 10 cages constructed on top of transite tables. We used 2 x 2 wood framing covered with 2 layers of 6 mil plastic containing ultraviolet inhibitors. Cages are 4 x 8 feet x 4 feet high, and each is divided into 4 isolation compartments. We have the capacity, therefore, to control pollination on 40 different lines at the same time. The greenhouse is cooled by 4 large forced air evaporative coolers, an automated top-venting system, side vents, and saran shade cloth. Heating is provided by 6 gas wall units.

Cool air or warm are is conveyed into each isolation compartment through a 4-inch galvanized stove pipe equipped with a damper. Connected to the stove pipe is a flexible 4-inch air conveyor tube which leads to an underground tunnel extending the full length of the greenhouse. The tunnel is 3 x 3 feet, constructed of concrete and insulated with one inch of Styrofoam glued to the inside walls. Controlled temperature air is conducted into the tunnel from heating and cooling units installed outside the greenhouse. These are controlled by a thermostat located, by trial and error, in an isolation chamber most representative of the system. The heating and cooling units consist of two 3-ton commercial units with heat pumps connected in tandem so as to supply 2 stages of heating and cooling. One stage operates if the outside air temperature range is between 70-85 degrees Fahrenheit or from 30-55 degrees Fahrenheit. The second stage begins when outside temperatures are more extreme.

All air moving through the system into the isolation compartments is outside air and free of spinach pollen. It moves ultimately into the
greenhouse through holes bored in the transite floor of compartments. Maintenance of positive pressure in compartments prevents entrance of foreign pollen through floor holes. A turbulator is used to mix greenhouse air and promote more uniform temperatures throughout.

Many details of the system have been omitted. If further information is desired, write the Department of Horticulture and Forestry, University of Arkansas.

7. Cucurbita Martineezii as a Source of Disease Resistance

H.M. Munger

Cornell University, Ithaca, New York 14853

In the fall of 1972, Dr. T.W. Whitaker showed me some plants of Cucurbita martineezii and said they probably had the highest level of resistance to powdery mildew of any species crossable with cultivated cucurbitas. He generously provided some seed, and our greenhouse tests confirmed its near-immunity. However, it is very difficult to get flowers on the species at Ithaca, and it was not until the late summer of 1974 that Rodney Sttetner's watchfulness enabled him to pollinate some female flowers of
'Butternut' (C. moschata) with the very few males produced by C. martineezii.

The resulting F1 showed a high level of PMR both in the greenhouse and in the field in 1975. Its resistance is not as high as the resistant parent but far closer to it than to Butternut. Max Contin is studying the inheritance of resistance and its transfer to cultivated squashes of various species. The F1 showed no clear symptoms of mosaic (CMV) in the field in 1975 while melons nearby were severely affected. Both parents and the F1 were inoculated with CMV as young seedlings in the greenhouse in the fall of 1975. Again, C. martineezii and the F1 showed no symptoms while they were severe on Butternut. Two months after the inoculation, virus could not be recovered from the former two lots. Further testing is needed to confirm this apparent mosaic resistance, but at this point it looks more promising than other sources of CMV resistance we have found.

8. Evaluation of 15125 x 1453 ae du wx High Sugar Maize Hybrid

D.L. Garwood, Sandra Vanderslice, and W.C. Garman

Department of Horticulture, The Pennsylvania State Univ., University Park, Pa. 16802

The amylase extender (ae) dull (du) waxy (wx) genotype continues to show promise as a high sugar sweet corn type with improved post-harvest sugar retention properties. In 1975, total sugar content of the 15125x 1453 ae du wx hybrid was determined at 15, 18, 21, 24, 27, and 30 days after pollination. Total sugar contents expressed as a percentage of dry weight were 53.9, 40.1, 27.2, 26.4, 22.1, and 20.6% for these sampling dates. Expressed on a per kernel basis 16.7, 19.8, 19.7, 25.3, 25.9, and 24.2 mg of sugar were present at 15 through 30 days after pollination. This data indicates that high levels of sugar are present for at least a 10-day period. Other data from our laboratory has demonstrated that high levels of sugar are still present after 96 hr storage at both 4?C and 27?C.

Yielding ability of the 15125 x 1453 ae du wx hybrid was evaluated using a Latin Square design with plant populations of 12, 16, 20, and 24 thousand plants per acre in 450 sq. ft. plots. Plots were planted May 23, 1975 and harvested August 19, 22, and 25. The highest yield, 4.42 tons per acre of unhusked ears, was obtained with 20,000 plants per acre. The lowest yield 3.67 tons per acre occurred at the lowest plant population. Results indicate that acceptable yields can be obtained using ae du wx genotypes. Additional evaluations of horticultural characteristics of this promising genotype are continuing.

9. Sweet Corn Breeding Questionnaire Summary

D.L. Garwood

Department of Horticulture, The Pennsylvania State Univ., University Park, Pa. 16802

Information has been compiled concerning (1) maintenance of publicly released su inbreds, (2) maintenance of publicly released du, sh2, and su2 inbreds in sweet corn backgrounds, (3) open pollinated sweet corn (su) variety maintenance and (4) mutant genes being incorporated by backcrossing into sweet corn inbreds and varieties. Copies of the summary are available upon request. Information from individuals not previously contacted would be appreciated.

10. Uncatalogued Vegetable Varieties Available for Trial in 1976

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 one source, the address is given only for the first.

11. Stocks Desired

Requests from Dr. J.L. Bowers, Dept. of Horticulture and Forestry, University of Arkansas, Fayetteville, Arkansas 72701: