Genetic worth and stability of selection indices in rice (Oryza sativa L.)

Improvement of one trait on its own will affect the performance of other traits because of genotypic correlations between traits. Index selection is one of the tools used by plant breeders to overcome this problem. The purpose of this paper is to evaluate selection indices developed for improving grain yield in rice (Oryza sativa L.). Forty-nine rice genotypes were cultivated at Tonekabon Rice Research Station, Iran, in 2009 and 2010. Selection indices were developed based on phenotypic and genotypic correlations, path coefficients, broad-sense heritability of traits and stepwise multiple linear regression coefficients. Assessment of indices revealed that the stability decreased concurrently with increase in the genetic worth, and hence an inverse association existed between stability and genetic worth of indices. The results also suggested that selection for TP, GW, GP and GL and against PH using their multiple linear regression parameters as economic weights was an effective criterion for improving grain yield in rice genotypes. On the other hand, the most stable indices were those that were developed based on heritability of traits as well as genotypic path coefficients.