combining ability and heterosis in rice (oryza sativa l.) cultivars

quantitative valuations of observed heterosis for 11 traits of 15 f1 hybrids generated by half diallel crosses of six diverse rice cultivars (domsefid, hashemi and binam, three iranian local cultivars; dorfak, kadous and ir30, three improved cultivars), were made in this study. fifteen f1 hybrids and their parents were evaluated in a randomized complete block design with three replications at the research farm of the university of guilan at rasht, (iran) in 2006. the studied traits were growth period, reproductive period, flag leaf area, plant height, panicle length, number of panicles per plant, number of grains per panicle, 1000-grain weight, grain yield, brown grain length and brown grain width. the significance of specific combining ability (sca) and general combining ability (gca) for all studied traits revealed that both additive and non-additive gene effects contributed to the inheritance of the traits. assessment of standard heterosis based on check variety dorfak showed that there was significant heterosis for all the traits studied in the 15 hybrids. for grain yield, the dorfak×domsefid cross had the highest heterosis. this hybrid had good heterosis values for many traits such as growth period, reproductive period and 1000-grain weight and was recommended as the most promising combination for developing high yielding hybrid rice varieties.