EPISTASIS FOR 3 GRAIN-YIELD COMPONENTS IN RICE (ORYZA-SATIVA L)

The genetic basis for three grain yield components of rice, 1000 kerne l weight (KW), grain number per panicle (GN), and grain weight. per pa nicle (GWP), was investigated using restriction fragment length polymo rphism markers and F-4 progeny testing from a cross between lice subsp ecies japonica (cultivar Lemont from USA) and indica (cv. Teqing from China). Following identification of 19 QTL affecting these traits, we investigated the role of epistasis in genetic control of these phenoty pes. Among 63 markers distributed throughout the genome that appeared to be involved in 79 highly significant (P < 0.001) interactions, most (46 or 73%) did not appear to have ''main'' effects on the relevant t raits, but influenced the trait(s) predominantly through interactions. These results indicate that epistasis is an important genetic basis f or complex traits such as yield components, especially traits of low h eritability such as GN and GWP. The identification of epistatic loci i s an important step toward resolution of discrepancies between quantit ative trait loci mapping and classical genetic dogma, contributes to b etter understanding of the persistence of quantitative genetic variati on in populations, and impels reconsideration of optimal mapping metho dology and marker-assisted breeding strategies for improvement of comp lex traits.