Correlation between molecular marker distance and hybrid performance in US southern long grain rice

Improving grain and milling yields of long-grain rice (Oryza sativa L,) continues to be a major objective of southern U,S, breeding programs, The objective of this study was to determine the relationship between molecular marker polymorphism of the parents and performance of the F-1 hybrids, A diallel cross was made by intermating eight Lines commonly used in U.S, southern long-grain rice breeding programs, The 28 F-1 hybrids and the parents were evaluated for rough rice yield, head rice percentage, and head rice yield in replicated field trials, Very little heterosis was detected among hybrids for head rice percentage, whereas heterosis was high for rough rice yield and head rice yield, A survey for DNA polymorphisms with 82 RFLPs and 26 microsatellites revealed high levels of variation among the eight parents. A cluster analysis resolved these eight lines into indica (one line) and tropical japonica (seven lines) rice subgroups, A majority of the markers detected statistically significant effects on one or more traits by an analysis of variance, Marker F-1 heterozygosity was highly correlated with rough rice yield (0.79**) and head rice yield (0.82**), and was also significantly correlated with heterosis of these two traits (0.47*, 0.58**, respectively). However, the correlations were largely attributed to the concurrence between high levels of heterozygosity and high performance in crosses between the indica variety Jasmine 85 and the remaining seven lines, Compared with the data published in previous studies, it was concluded that the level of correlations between marker distance and hybrid performance is dependent on the germplasm used.