2017 Volume 62 Pages 19-23
Asian cultivated rice Oryza sativa L. has been known to be domesticated from wild rice, O. rufipogon. During domestication, agronomically suitable traits were selected, including a loss of seed shattering. In previous studies, three quantitative trait loci (QTLs), sh4, qSH1, and qSH3, were found to be involved in the non-shattering behaviour of O. sativa Japonica ‘Nipponbare’. In contrast, O. sativa Indica ‘IR36’ has cultivated alleles at sh4 and qSH3, but a partial abscission layer formation has been observed. Differences in the seed-shattering degree between Japonica and Indica rice are mainly accounted for by the genotypes at qSH1. However, the allele effects at the loci controlling the non-shattering behaviour of Indica rice are not known clearly. We previously produced an introgression line (IL) carrying O. sativa Japonica ‘Nipponbare’ cultivated alleles at sh4 and qSH3 in the genetic background of wild rice O. rufipogon W630. Although this introgression line (hereafter IL(3+4)) has the same genotypes at sh4 and qSH3 as O. sativa Indica ‘IR36’, it has a well-formed abscission layer compared to that of IR36, resulting in very easy-shattering like wild rice. To understand the independent effects of sh4 and qSH3 on non-shattering behaviour of ‘IR36’, we evaluated the F1 and F2 plants between ‘IR36’ and IL(3+4). In F1 plants, the formation of a clear abscission layer was observed in a manner similar to that of IL(3+4), suggesting that ‘IR36’ may harbour recessive allele(s) at unidentified seed-shattering loci. We also observed the segregation of seed-shattering behaviour in the F2 population, confirming that other unknown mutation(s) may underlie the non-shattering behaviour of ‘IR36’.
