Peroxidase and IAA‐oxidase activity, electrophoretic patterns of total proteins and isoenzymes and the effect of Ethephon (= Ethrel, 2‐chloroethane phosphonic acid) on these patterns were compared in extracts of monoecious and gynoecious cucumber plants. The activity of both peroxidase and IAA oxidase was greater in gynoecious than in monoecious plants. Ethephon treatments given at the 2‐leaf stage increased peroxidase activity, especially in monoecious plants, and decreased IAA‐oxidase activity. Ethephon treatment did not affect total protein or isoenzyme patterns, but increased band intensity, especially that of one band in monoecious plant extracts. No differences between monoecious and gynoecious plants were found in total protein, peroxidase and IAA‐oxidase isoenzyme patterns. Peroxidase and IAA‐oxidase activity sites on the gel were similar.
Significant deviations from the ratios expected, according to the single dominant gene hypothesis for resistance to Fusarium wilt, were found in crosses involving several susceptible and resistant tomato lines. The susceptible class was the deficient one in F 2 and in F 3 populations, as well as in backcrosses in which the heterozygotic resistant F 1 served as the male parent. The reciprocal backcross, with the F 1 as the female and the homozygous susceptible as the male, gave segregations better approximating or consistent with the single gene hypothesis. Reciprocal F 1 and F 2 generations did not give any evidence of cytoplasmic effects.The results were interpreted assuming preferential fertilization of ovules by pollen grains carrying the dominant I allele for resistance.The practical implications of the phenomenon of preferential fertilization in breeding for Fusarium resistance are discussed.
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