Abstract
Eight test varieties were chosen and were crossed with each of 47 varities (30 upland rice and 4 'red rice' from Japan and 13 Eastern Asian countries) to examine mutual sexual affinity among rice varieties. The sexual aflimity was measured by the percentage of viable pollen in F1 hybrids. The results are summarized as follows : 1. No difference was found between reciprocal crosses (Fig. 1). 2. The pollen fertility of the F1 hybrids was different with the combination of parental varieties and ranged discontinuously from about 100% to O% (Table 2) . 3. It seemed that F2 variation for intervarietal hrybrid sterility was discontinuous and that the modes observed in F2 variation were coincident with those in intervarietal combinations (Table 3). The intervarietal hybrid sterility could be accounted for by duplicated genes (Table 4) . 4. From the observation of anomalous segrega-tions for anthocyanin pigmentation and glutinuous character, it. was assumed that the duplicated genes belonged frequently to "wx"-group (Table 6) . 5. By separating the varieties with similar affmity to each of the test varieties, Japanese upland rice was divisible in to three groups. Group I, to which most varieties belonged, was again classified into two types, corresponding to 'Lowland Type' and 'Upland Type' respectively (Fig. 2).
