estimation of heritability and heterosis of some agronomic traits and combining ability of rice lines using line × tester method

in order to determine combining ability, heritability and heterosis of some agronomic traits in rice, 4 pure lines were crossed with 2 cytoplasmic male sterile testers. parents and their f1 progenies arranged in rcb design with three replications. analysis of variance showed significant differences among genotypes for all traits, except for filled grains/panicle. furthermore, the crosses effect was significant for all traits at 1% level. existence of additive and non-additive effects was observed on controlling of given traits. combining ability analysis showed that there was significant gca for some of parents in all traits except for panicle length and tillers/plant. the highest gca in yield (105.3 g/m2) was obtained for line 1. sca was only significant for plant height (combinations: l1×t1 and l1×t2), panicle sterility and 1000-grain weight (combinations: l3×t1 and l3×t2). share of additive and non-additive variations was not identical in various traits, and different values of heritability were observed based on genetic additive effect. the highest specific heritability (hn) was observed for 1000-grain weight (41.7%). average specific heritability observed for total grains/panicle, plant height and yield results in relatively low efficiency of selection of the lines with desirable characters. it seems that selection for further tillers and longer panicle will not be successful because of low specific heritability. the highest heterosis in yield (26.1%) was obtained for l1×t1 cross.