Effect of cropping system on genetic variability and component analysis in soybean

The nature and magnitude of genetic variability and component analysis was assessed in 50 diverse genotypes of soybean grown in monoculture and in association with maize. Cropping system effects and interaction of cropping systems with genotypes were significant for all traits except 100-seed weight, oil % and protein %. Branches/plant, total pods/plant, pod clusters/plant, harvest index and seed yield/plant decreased under intercropping. There was no effect of cropping system in the manifestation of phenotypic and genotypic variability. The estimates of heritability and genetic advance for seed yield components were less in the associated cropping system than in the sole crop. Genotypes interacted differentially to the different cropping systems. The performance of as many as 30 genotypes was comparable under both cropping systems. Fourteen genotypes recorded reduction in seed yield/plant under intercropping. However, the performance of six genotypes was higher under intercropping. Among the commercial varieties, the performance of ‘Bragg’ and ‘Hardee’ was comparable under both cropping systems. ‘Punjab-1’ performed better in associated cropping, while ‘Shilajeet’ and ‘Lee’ performed better under sole-crop.The correlation coefficients between traits were found to differ, both in nature and magnitude, between monoculture and intercropping. In monoculture, seed size, harvest index and oil % were positively related with seed yield. By contrast, plant height, branches/plant, pods/plant and pod clusters/plant, besides 100-seed weight and harvest index, were correlated with seed yield under intercropping. Seed size followed by branches/plant appeared to be the important characters to undertake selection for higher seed yield under sole-crop. Yield improvements in intercrop were associated with increased harvest index. Genotypes and the characters to be utilized to develop varieties suitable for sole-crop and intercropping have been suggested.