Marker Genotypes for Parents of Japonica Hybrid Rice with High Combining Ability of Yield Traits

Scarcity of restorer line with high combining ability is a crucial restraint in the extension of japonica hybrid rice (Oryza sativa L.). This study aimed to screen simple sequence repeat (SSR) marker genotypes that can efficiently reveal high combining ability of hybrid parents. A total of 115 candidate markers were amplified in 6 BT-type cytoplasmic male sterile (CMS) lines and 12 restorer lines. Daily yield per plant (DYP), number of productive panicle per plant (PP), total number of spikelet per panicle (TSP), number of filled spikelet per panicle (FSP), and thousand-grain weight (TGW) were investigated in the 18 parents and 72 F₁s derived from the crosses under an NCII design. Twenty marker genotypes were significantly associated with combining abilities (CA) of the parents. Among them, 12 marker genotypes were related to CA for more than one trait simultaneously, and the remaining 8 marker genotypes were only related to CA for one trait. The effect direction of marker genotype on combining ability of multiple traits was either positive or negative. RM152-165/170 was a marker genotype with the largest combining ability of PP and DYP, which increased DYP and PP in F₁ by 20.6% and 12.7%, respectively. The marker genotypes with positive effect on increasing yield can be applied directly in the combining ability improvement of japonica rice restorer lines.