The application of selection indices on improvement of grain yield in rice (Oryza sativa L.)

Grain yield and most of traits that have economic important in plants and animals، herited as quantity and using direct selection method have not large progress. So one of the most effective methods indirect selections as improve grain yield with trait effective on it، is using of selection index. In this research، six rice cultivars were crossed in half diallel design in 2005. In the next year، parents and their progenies were grown in a randomized complete blocks design with three replications and 22 traits were measured. Stepwise regression was done for 22 trait and 7 following traits were selected: number of panicles/plant، number of grains per panicle، 1000-grain weight، spikelt width، number of spikelts/panicle and plant height and used to estimation of selection indices. Index selection is one of the most effective indirect selection methods for improving grain yield and other important traits. Estimating five different selection indices based on optimum and base indices indicated that selecting for number of panicles/plant and number of grains per panicle by using their stepwise regression and path direct coefficients as economic weights would be a suitable selection criterion for improving of population. Moreover، this study showed that both optimum and base indices presented the same genetic advance for traits studied. The base index، however، is much easier to evaluate than the optimum index، and is recommended.