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  • Author or Editor: E.V. Wann x
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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.

Open Access
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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.

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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.

Open Access
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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.

Open Access
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Tissue firmness of ripe tomatoes is controlled by cell wall integrity of the fruit tissue and by the enzymatic softening that normally occurs during ripening. This study was conducted to determine the physical characteristics of cells and tissues of mature green (MG) and ripe fruit that might account for differences in firmness between `Rutgers' (normal), `Flora-Dade' (Firm), and two mutant lines called high-pigment (T4065 hp) and dark-green (T4099 dg), both of which possess extra firm fruit. Fruit samples were tested for resistance to a force applied to whole fruit and to sections of the pericarp tissue and by stress-relaxation analysis. Determinations were also made of cell density and cell wall content within the pericarp tissue. Fruit of mutant lines had firmer tissue than either `Rutgers' or `Flora-Dade' at MG or ripe. Whole fruit compression measurements showed that T4099 dg was firmer than T4065 hp or `Rutgers' at MG and firmer than `Flora-Dade' and `Rutgers' when ripe. Whole fruit of `Flora-Dade' were significantly firmer than `Rutgers' at MG and ripe. Firmness measured by compressive strength also showed that mutant lines had firmer pericarp tissue than the wild types at both MG and ripe stages. Stress-relaxation analysis showed that MG fruit of T4099 dg had greater tissue elasticity than `Rutgers' or `Flora-Dade'. Ripe fruit of both mutant lines had more tissue elasticity than wild types. There were no apparent differences among the genotypes due to tissue relaxation. From these analyses, tissue elasticity appears to be a significant parameter in determining tissue firmness in the tomato genotypes used in this study. Firmness and textural quality of ripe tomatoes appeared to be dependent on elasticity of the pericarp tissue and on the level of enzymatic softening during ripening.

Free access
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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.

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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.

Open Access
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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.

Open Access

Abstract

An antibiotic type of resistance has been demonstrated in sweet corn inbred lines and hybrids by periodic growth measurements of corn earworm larvae feeding on resistant and susceptible types. Resistant types could be distinguished readily from the susceptible by a significant increase in larval mortality on the former. Resistant lines also retarded larval growth, decreased depth to which larvae penetrated the ear, and delayed pupation of the insect.

Open Access