Relationship between molecular marker heterozygosity and hybrid performance in intra- and inter-subspecific crosses of rice

The objective of this study was to investigate the relationship between mol ecular marker diversity and heterosis in both intra-and inter-subspecific h ybrids of rice to evaluate the feasibility of predicting hybrid performance using molecular markers. Eleven elite lines were intermated resulting in a diallel set including 10 indica x indica, 15 japonica x japonica and 30 in dica x x japonica crosses. The F-1 hybrids and parents were evaluated for a gronomic performance in a replicated field trial. The parental lines were t ested for DNA polymorphisms with 113 restriction fragment length polymorphi sm (RFLP) probes covering the 12 rice chromosomes. Inter-subspecific crosse s showed better performance and higher heterosis than intrasubspecific hybr ids. Correlations of marker heterozygosity with hybrid performance and hete rosis differed considerably between the two subspecies; they were higher in crosses within japonica subspecies than within indica ci subspecies. Very little correlation was detected in intersubspecific crosses. It was conclud ed that relationships between marker heterozygosity and hybrid performance were complex owing to germplasm diversity and the complexity of the genetic basis of heterosis. The implications of the results in predicting hybrid p erformance using molecular markers are discussed.