Abstract
Backcross populations are useful for evaluating the agronomic traits from unadapted germplasms. In this study, we produced 159 and 170 backcross recombinant inbred lines (BRILs) at the BC2F8 generation between Oryza sativa Japonica Nipponbare (a recurrent parent) and O. rufipogon W630 and between O. sativa Indica IR36 (a recurrent parent) and O. rufipogon W630, respectively. These BRILs were found to have nearly homozygous genome constitutions based on the marker genotypes at SSR loci covering whole chromosomes. Since their selfed progenies have almost identical genotypes in each line, the simple test tube method was applied for BRILs (BC2F9 generation) to evaluate the ability of fast shoot elongation after germination stage under submerged condition. Then, QTL analysis of submergence avoidance was carried out with marker genotype data. As a result, three (on chromosomes 2, 3 and 10) and two QTLs (on chromosomes 3 and 4) were found in the BRILs having genetic backgrounds of Nipponbare and IR36, respectively. Of these, one each had the wild allele with increasing effect on shoot length. These favorable wild alleles would be useful in improving direct-seeding cultivation in water-prone areas.
