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Abstract
Virus-free plants of 8 monoembryonic cultivars of Citrus Clementina Hort ex Tan. were obtained by somatic embryogenesis of the nucellus cultured in vitro. Twenty-nine percent of them had abnormal phenotypic characters that were maintained for 7 years in the greenhouse, and by bud wood propagation on different rootstocks. Electrophoretic studies of the proteins disclosed differences in band intensity and distribution between normal and abnormal plants, indicating the possibility of genotypic variations. Alternative methods to obtain virus-free citrus plants are advised to reduce the high percentage of abnormalities.
Abstract
Field grown onion plants (Allium cepa L. cvs. New Mexico Yellow Grano and Yellow Granex) harvested in December were frozen in a laboratory freezer were removed from the freezer at about 1°C intervals and replanted in sand in a warm greenhouse. Criterion for survival was root regeneration within 3 weeks. The LT50 value as determined by probit analysis for 58-day-old plants (−8.8°C) was significantly higher (0.5% level) than for the 74- or 90-day-old plants (−10.5 or−10.8°C) indicating less cold hardiness for the youngest plants.
Antioxidants, antioxidant capacity, and the expression of isoprenoid metabolism–related genes and two pigmentation-related transcription factors were studied in four native and four hybrid tomato (Solanum lycopersicum) genotypes with different-colored fruit. Red fruit genotypes were associated with greater lycopene, β-carotene, lipophilic antioxidant capacity, and greater chromoplast-specific lycopene β-cyclase (CYC-B) transcript levels. Orange fruit genotypes had greater concentrations of tocopherols and greater transcript levels of homogentisate phytyl transferase (VTE-2), 1-deoxy-D-xylulose phosphate synthase (DXS), and 4-hydroxyphenylpyruvate dioxygenase (HPPD). The yellow fruit genotype was greater in total polyphenol and hydrophilic antioxidant capacity with greater expression of geranylgeranyl reductase (GGDR), phytol kinase (VTE-5), phytoene synthase (PSY) 2, lycopene β-cyclase (LCY-B), SlNAC1, and SINAC4. Greater levels of individual antioxidants were associated with specific coloration of tomato fruit. Moreover, the negative correlations between the expression of PSY1 and VTE-5, and between lycopene and chlorophyll, suggest a balance between carotenoids, tocopherols, and chlorophylls. The results of this study support either the direct commercialization of tomatoes with different color fruit or use of their genotypes in breeding programs to increase antioxidant levels among existing cultivars.