QTLs for Grain Yield and Yield Related Traits in Indica-Japonica Crosses of Rice

To identify QTLs for grain yield (GY) and yield-related traits in indica-japonica crosses, we used two RIL populations. One RIL population is composed of 166 F₈ RILs derived by the single-seed decent method from a cross between Milyang 23 (a Korean tongil-type indica variety) and Tong 88-7 (a temperate japonica variety). The other RIL population of 179 F₁₁ RILs was derived from a cross between Dasanbyeo (a Korean tongil-type indica variety) and TR22183 (a temperate japonica variety). The major GY QTLs were detected on chromosomes 1 and 7 in the Milyang 23 / Tong 88-7 RIL population and chromosomes 8 and 9 in the Dasanbyeo / TR22183 RIL population. No common GY QTLs were detected between the two populations. However, all of the GY QTLs were detected in same regions as the yield component QTLs in each population. This result confirms that GY was highly correlated with yield-related traits in these populations. In path coefficient analysis, yield component traits showed a highly positive direct effect on GY. Moreover days to heading, culm length, and panicle length showed a strong indirect effect on GY through a direct effect on spikelet number and spikelet fertility. These results suggest that panicle-related traits contribute to higher yields across various heading time and plant height profiles, even though the related QTLs/genes may be present in different chromosomes from different varieties. This work was supported by a grant from the Next-Generation BioGreen 21 Program (Plant Molecular Breeding Center, No. PJ009076), Rural Development Administration, Republic of Korea.