an evaluation of the relationship between grain yield & biological yield, and some important agronomic traits in soybean, using path analysis

in order to determine the relationship between the variables grain yield and biological yield and some important agronomic traits, and to find the direct and indirect effects of important agronomic traits on both grain and biological yields, 364 soybean genotypes (3 planting dates) were studied. the study was based on a design augmented with 3 checks and 6 blocks implemented, in seed and plant improvement institute, karaj, iran, during 2003-04 growing season. the results of simple correlation indicated that the biomass, number of seeds as well as number of pods per plant were in a high correlation with seed yield per plant for all the planting dates. also seed yield, number of nodes in main stem at the beginning of maturity stage, number of seeds as well as number of pods per plant were in a high correlation with biological yield. the results of stepwise regression and path analysis showed that number of seeds per plant and 100 seed weight exerted the greatest positive effects on both grain yield and biological yield for all planting dates. the results therefore suggest that the number of seeds per plant and 100 seed weight be can used as selection criteria in soybean grain and biological yield improvement.