| Abstract
| - Summary. The inheritance of protein content in rice was studied in the six possible hybrid populations among four varieties: Calrose from the USA, Ku Jung Do from Korea, and Kitaminori and Isao Mochi from Japan. Each population consisted of 100 random lines. Standard unit heritabilities for the correlation of F2 panicle values with F3 hill-plot protein values were not significantly different from zero, and variance component heritabilities for F3 hill-plots were low. Among the F3 populations significant genetic variation for protein content was observed in the crosses of Ku Jung Do × Calrose, and Kitaminori × Calrose. Genotypic, phenotypic, and environmental estimates of correlations among protein content, kernel weight, heading date, and plant height were examined. High protein content was significantly correlated with light kernels, early heading, and short stature. Low protein heritabilities were tentatively attributed to genotype × year interaction, to an environmental gradient affecting protein content in the field, and to within-line segregation for the early generations tested. It was suggested that selection for protein content be deferred until later generations. However, selection for high protein content may in some cases be incompatible with selection objectives for other traits.
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