Heterosis and diallel analysis for yield and some morphological traits in rice (Oryza sativa L.)

To evaluate the combining ability, gene action and heterosis for morphological traits in rice, F2 progenies of a 6×6 half diallel crosses with their parents were planted in a randomized complete block design with three replications at Rice Research Institute of Iran, Rasht, Iran, in 2015. Analysis of variance indicated that genotypes were significantly different for all measured traits. The results of diallel analysis by the second method of Gardner-Eberhart revealed that the variety effect was significant for all the studied traits. The effects of heterosis, average heterosis, variety heterosis and specific heterosis was significant for grain yield (GY), days to heading (DTH) and flag leaf length (FLL). Parents IR50 and RI18447-2 had the greatest positive and significant amount of general combining ability. The highest amount of specific combining ability was observed for IR50×RI18430-46 cross. Analysis of diallel by the third method of Gardner-Eberhart demonstrated existence of both additive and non-additive effects in genetic control of GY, DTH and spikelet’s number (SN). Heterobeltiosis and relative heterosisfor GY ranged from-35.03% to 17.16% and -28.59% to 24.01%, respectively. The sharpest decline in heterobeltiosis and relative heterosis for plant height (PH) was -14.36% and -12.73%, respectively. For panicle length (PL) no significant amounts of heterosis found in crosses. The range of heterobeltiosisfor SN was from -33.44% to 1.58%. According to combining ability, presence appropriate amounts of additive gene effects and heterosis for most of the studied traits, it is possible to breed these traits by using both the selection and hybrid production methods in the studied population.