A DIALLEL ANALYSIS OF HETEROSIS IN ELITE HYBRID RICE-BASED ON RFLPS AND MICROSATELLITES

Hybrid rice has contributed significantly to the dramatic increase of rice production in the world. Despite this, little attention has been given to studying the genetic basis of heterosis in rice. In this pape r, we report a diallel analysis of heterosis using two classes of mole cular markers: restriction fragment length polymorphisms, (RFLPs) and microsatellites. Eight lines, which represent a significant portion of hybrid rice germ plasm, were crossed in all possible pairs, and the F (1)s were evaluated for yield and yield component traits in a replicat ed field trial. The parental lines were surveyed for polymorphisms wit h 117 RFLP probes and ten microsatellites, resulting in a total of 76 polymorphic markers well-spaced in the rice RFLP map. The results indi cated that high level heterosis is common among these crosses: more th an 100% midparent and 40% better-parent heterosis were observed in man y F(1)s, including some crosses between maintainer lines. Heterosis wa s found to be much higher for yield than for yield component traits, w hich fits a multiplicative model almost perfectly. Between 16 and 30 m arker loci (positive markers) detected highly significant effects on y ield or its component traits. Heterozygosity was significantly correla ted with several attributes of performance and heterosis. Correlations based on positive markers (specific heterozygosity) were large for mi dparent heterosis of yield and seeds/panicle and also for F-1 kernel w eight. These large correlations may have practical utility for predict ing heterosis.