Inheritance of partial resistance to leaf blast (P. oryzae) [Pyricularia oryzae] in some rice varieties.
1987
Wang Ziming
Genotypic variability among parents was observed for lesion number and lesion size and there were significant differences between resistant and susceptible parents for lesion number. For lesion size, the difference between the resistant parent, IR36, and the two susceptible parents, IR50 and Milyang 57, was significant but the difference between resistant parent Milyang 42 and susceptible parent Milyang 57 was not. The F1 was similar to the resistant parents in lesion size. Partial resistance in terms of lesion number was probably controlled by a polygenic system and lesion size might be controlled by polygenes or oligogenes. The moderate value of broad-sense heritability from 0.20 to 0.50 for lesion number and 0.35 to 0.67 for lesion size indicated that a certain proportion of phenotypic variance was genetic. The narrow-sense heritability ranged from 0.18 to 0.38 for lesion number and 0.30 to 0.43 for lesion size. Based on these estimates, the predicted gain from selecting the 10% best F2 plants were 8% to 16% for lesion number, and the predicted gain from selecting the 5% best F2 plants were 23% to 36% for lesion size. The broad-sense heritability calculated from F2 and parental variance of ADPC ranged from 0.14 to 0.16 for cross resistant x susceptible and zero for resistant x resistant parents. Significant differences between resistant and susceptible F3 family lines from selected F2 plants were observed for crosses between resistant and susceptible parents but not significant for a cross between resistant parents in lesion number and lesion size. Selection of F2 plants was effective for increasing partial resistance to lesion number or lesion size.
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