Mechanism of recoveiring of fertility in autotetraploid rice.

Abstract

According to recent knowledge, the reduced fertility of autotetraploids seems to be somewhat recovered by hybridization between themselves or using diploid hybrids as original plants to induce tetraploids. But it is not clear enough at what degree of heterozygosity in parental diploid species or hybrids. In rice, Oryza sativa L., we have many varieties cultivated throughbut the world, especially ih Eastern Asia which are, classified into t.wo subspecie.s, Japoleica and ludica, On the standpoint of, varietal hybrid sterility, these subspecies are classified into three categories, natnely, the fertile group, semisterile group, and sterile group by TERAO and MIZUSHIMA (1943). Three groups, namely I, , II, and III are considered by them for its phylo.genetic relaticnships to be near or less familiar on this order due to their sexual affinities. If we induce tetraploids of IxI; IxII. IxIII and IIXIII, we can compare the effedts of various degrees of hetero zygosity on seed fcrtility of autotetraploids. And also we can expect that the ireeovery of reduced fertility of tetraploids is mostfy promote in IxIII group which is considered as the, most unfamiliar group.