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- Author or Editor: E. V. Wann x
- HortScience x
Abstract
Composite 9E-79 is a mid-season, earworm-resistant sweet corn (Zea mays L.) that will provide plant breeders a useful source of germplasm from which superior inbred lines may be extracted. It will also serve as a reservoir for the conservation of valuable sweet corn germplasm.
Abstract
Genetic engineering is a relatively recent concept in the science of genetics and plant breeding. Although systematic efforts toward genetic improvement of crop plants are as old as agriculture itself, this new concept utilizes a vastly different approach. It includes cell culture, protoplast fusion, and recombinant DNA. Indeed, genetic engineering has emerged as a result of recent advances in laboratory techniques and the knowledge of cell physiology and molecular biology. The basic research leading up to the development of this new technology was begun many years ago in laboratories devoted to studying cell physiology, plant growth regulators, and, most importantly, the structure and chemical nature of DNA, the basic unit of heredity. Simply defined, genetic engineering is the application of special techniques to modify DNA and to incorporate the restructured DNA into a suitable host for the purpose of changing its heritable characteristics.
Absrtact
The long gray melon from Charleston, called ‘Charleston Gray’, for more than two decades has been the most widely grown cultivar. It is prominent throughout Europe and Asia. In 1979 it was found growing in Heilongiang, the northernmost province of China and is a leading cultivar in the Shaanxi Province in central China. Since its release in 1954, ‘Charleston Gray’ has pleased growers, shippers, and consumers with its high yields, superior quality, and outstanding shipping ability, and in recent years many of its indirect descendants have begun to be important in the industry.
Abstract
The Southern Tomato Exchange Program (STEP trials) was begun in October 1945 by a group of state and federal scientists for cooperative tests of tomato breeding lines. The program was made a part of the Southern Cooperative Vegetable Trials, which are now under sponsorship of the Southern Section of the American Society for Horticultural Science. Participation includes about 20 people representing 16 states, Puerto Rico, and the U. S. Department of Agriculture. In 1968, the STEP trials were separated into two sections, one for fresh-market types and another for processing types. In 1973, the decision was made to add a section for testing lines developed especially for once-over machine-harvesting for fresh market. So far, in the fresh-market section of the trials, 621 tomato lines have been tested, 50 of which were released as cultivars. That yields from the best entries in the trials have almost doubled over the years may be attributed largely to their resistance to diseases. It is anticipated that the STEP trials will continue to serve as a medium for cooperation among tomato breeders.
Research was conducted to determine the reliability of several techniques for measuring the response of cucumber to low-moisture stress. Low and high moisture stress levels were imposed in field plots by differential irrigation. Plots under low stress (high soil moisture) had a mean tensiometer reading of 9±1.0 cb during the evaluation period, and plots under high stress had a mean tensiometer reading of 37±2.3 cb. Six genotypes of diverse backgrounds were evaluated for their stress response. The drought-tolerant cultivars `Alagi', W142121, and WI1983LL (Little Leaf) showed least response to the imposed stress. Visual ratings and stress index were correlated with moisture stress levels and they detected differences in stress response among cultivars. Plant water content, stomatal conductance, and transpiration rate were least reliable for measuring moisture stress. Visual ratings appeared to be as reliable as the other more quantitative types of measurements for detecting stress tolerance.
Abstract
Pickle worm [Diaphania nitidalis (Stoll)] and melon worm [Diaphania hyalinata (L.)] moths, released into a screenhouse, laid far more eggs on pubescent than on glabrous plants of cucumber (Cucumis sativus L.). In a field test of the 2 foliage types, a total of 8 times as many melonworm larvae were found on pubescent as glabrous plants, but about the same number of pickle worm larvae were found on both types. Both melonworm and pickleworm moths laid approximately equal numbers of eggs on fiberglass insulation treated with ethanol extracts of the 2 foliage types, suggesting that the presence or absence of pubescence on the leaves determined oviposition preference.
Abstract
Tandem mass selection in a sweet com (Zea mays L.) composite produced a 5-day gain in maturity, increased the percentage of plants with light-colored silks, and increased the number of kernel rows per ear. Although the differences in earworm resistance between generations were not statistically significant, they suggest a slight but steady increase through the first four cycles of selection. Because infestation of earworm [Heliothis zea (Boddie)] was very low in 1972, no selection was applied to the fifth generation for resistance, and the level of resistance based on mean larval weights and larval instars dropped. Tandem mass selection improved the sweet com population for certain agronomic characters, and maintained its level of earworm resistance.
Increased peroxidase activity is used to predict development of off-flavor in frozen sweet corn. However, peroxidase activity was not indicative of flavor changes in frozen supersweet (sh2) or sugar enhanced (sul/se) sweet corn genotypes. These results suggested an inactivation or absence of certain peroxidase isozymes. Frozen `Florida Staysweet' (sh2), `Merit' (sul), and `Bodacious' (sul/se) kernels were cut from cobs after 0 and 12 months of storage. Proteins extracted from acetone powders were separated by isoelectric focusing (IEF) and Native-PAGE. Banding patterns differed according to cultivar and storage duration. All cultivars contained a peroxidase isozyme having a molecular weight of 99 kD and pI of 4.5. The sul/se and su2 cultivars expressed an additional peroxidase band of 17.9 kD. An additional peroxidase isozyme (pI 5.0) appeared after 12 months of storage in the sul cultivar. This isozyme did not appear in sul/se or sh2 and is a possible marker for predicting off-flavor in corn. This isozyme may also catalyze off-flavor reactions in sul corn genotypes. Although changes in total peroxidase activity may not predict flavor loss in all genotypes, certain peroxidase isozymes may be useful in predicting and catalyzing off-flavor reactions in sul corn cultivars.
Supersweet corn with the shrunken-2 gene (sh2) has shown good quality after frozen storage. A study was undertaken to further evaluate the quality of supersweet corn (cv Florida Staysweet) unblanched or blanched then frozen. Samples were evaluated every 4 months for 12 months for peroxidase activity. sugar composition, water soluble polysaccharides and organoleptic qualities. Peroxidese activity changed in unblanched corn at each sampling date, which was consistently higher than in blanched corn. Sucrose and total sugars declined during storage. Sucrose was highest in blenched samples and reducing sugars were highest in unblanched samples. WSP content was low in all samples, but lower in blenched compared to unblanched samples. Taste panelists discerned differences between blanched and unblanched corn at 8 months when blanched samples were rated as more yellow than unblanched. However, no differences were found for taste between blanched and unblanched samples for taste at 12 months. These results indicate that sh2 sweetcorn maintained good eating quality for 12 months of frozen storage with or without blanching.