Distribution of the genes causing F2 chlorosis in rice cultivars of the Indica and Japonica types

Summary Chlorotic plants were segregated in F₂ populations in varietal crosses of common rice. The genetic basis and distribution of the genes causing F₂ chlorosis in native cultivars were studied to examine the role of the F₂ chlorosis in varietal differentiation of rice. It was proven that this F₂ chlorosis was controlled by a set of duplicate genes, hca-1 and hca-2. The hca-2 gene was widely distributed in native cultivars of the Japonica type, while many Indica types carried its dominant allele hca-2 ⁺. Japanese cultivar J-147 carried hca-2. The hca-1 gene was frequently distributed in cultivars containing the Hwc-2 gene for F₁ weakness. We concluded that F₂ chlorosis does not cause or promote varietal differentiation in rice.