Combining Ability of Yield-Component Traits for Indica Chromosome Substituted Segments in Japonica Hybrid Rice

Abstract

To study the heterosis of inter-subspecies hybrid in rice ( Oryza sativa L.), 10 chromosome segment substitution lines (CSSLs) with Asominori ( japonica) background derived from Asominori × IR24 ( indica) and the parent Asominori were crossed with 6 japonica tester lines (as male parents). A total of 66 combinations were planted in the field with NCII design. The 10 CSSLs had higher general combining abilities (GCAs) than the parent Asominori in the main yield-component traits, excluding the thousand-grain weight. Five CSSLs, AIS84, AIS27, AIS3, AIS80, and AIS76 with chromosome substitution segments from chromosomes 12, 4, 1, 11, and 11, respectively, ranked as the top 5 in the GCA of yield-related characteristics. The results showed stronger heterosis in the indica/japonica combinations at the chromosome segment level than in the typical japonica hybrid rice. Intentionally substituting japonica chromosome segments with indica counterparts, such as, X24–2– R367 in chromosome 12, R1854– R288 in chromosome 4, C970– C955 in chromosome 1, C1350– R257 in chromosome 11, and X52– R2913 in chromosome 11, could significantly promote the yield potential of japonica hybrid rice. Different combinations with one identical parent or different traits in the same combination had significant differences in the specific combining ability (SCA). Combinations with the highest and lowest SCA values were derived from different parental GCA groups, indicating no causal relations between SCA and parental GCA. High GCA combined with strong SCA is a basic principle of parental selection in the breeding programs of super high-yielding hybrid rice.