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- Author or Editor: E. V. Wann x
- Journal of the American Society for Horticultural Science x
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.
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.
Abstract
Carbohydrate analyses were made at harvest and after 7 days of postharvest storage at 65°F on sweet corn hybrid cultivars with endosperm mutant genotypes ae wx, ae du wx, and sh 2 and of standard sweet corn (su 1). Cultivars with the mutant genotypes contained from 1.5 to 2.0 times as much total sugar at harvest as the standard. They also lost more total sugar during the post-harvest period. Still, the hybrids with ae du wx and sh 2 genotypes contained significantly more sugars than the standard after the 7-day storage treatment. The mutant cultivars were low in water soluble polysaccharides but relatively high in starch. All cultivars had approximately the same amount of total carbohydrate. Moisture loss from the kernels during the storage period was significantly less in the mutant cultivars. Therefore, they maintained their fresh appearance longer, and they were slower than standard sweet corn to show kernel denting. Taste tests indicated a preference for the sweetness of the ae wx and ae du wx genotypes over the standard cultivars Golden Security and ‘Iobelle’ (Florida 104), but they were rated below the standards for pericarp toughness. These studies indicated that, with further refinement of certain horticultural and quality characteristics, the ae wx, ae du wx, and sh 2 endosperm mutant genotypes have a definite potential for improving the initial quality and the ability for maintaining good quality during normal post-harvest handling of fresh sweet corn.
Abstract
The mutant genotypes high-pigment/crimson (hp og c) and dark-green/crimson (dg og c) were evaluated for their effect on tomato fruit quality. Mature green fruit from the mutant genotypes had 2 to 3 times the amount of chlorophyll in the pericarp and mesocarp tissue as their genetically related but normal counterparts or the control ‘Flora-Dade’. Fruit of the mutant lines were firmer than ‘Flora-Dade’ or their normal counterparts at the mature green stage, as well as when fully ripe. The mutant genotypes conditioned an intense red color in the ripe fruit; the result of a 2-fold increase in carotenoid pigments, especially the red pigment lycopene. Ripe fruit of the mutant genotypes were higher in ascorbic acid (Vitamin C) and beta-carotene (Provitamin A) than normal, but they were slightly lower in total soluble solids. There were no significant differences in pH, alcohol insoluble solids, or total pectin among normal or mutant genotypes. Enzyme analyses showed higher polygalacturonase and β-galactosidase activity in the mutant genotypes than ‘Flora-Dade’ or the normal counterparts. Line T4077 dg og c had significantly less activity for these 2 enzymes than line T3995 hp og c. The dg og c line also had less activity for pectinesterase and invertase than any of the other lines, including its normal counterpart. The 2 mutant genotypes had similar effects on fruit quality characteristics. A sensory panel (n = 48) indicated no significant taste preference differences among the 5 lines.