Genetic Variability for Physiological Characters and their Relationships with Seed Yield and its Components in Indian Mustard [Brassica juncea(L.) Czern. & Coss.] under Drought

Abstract

Twenty-two genotypes of Indian mustard were grown in a randomized complete block design with three replications. Analysis of variance indicated presence of variability in the experimental genotypes for all the physiological characters investigated except specific leaf weight (SLW) at 35 DAS and seed: husk ratio. Phenotypic (PCV) and genotypic (GCV) variability was substantial for leaf growth rate (LGR), leaf area index (LAI), leaf area ratio (LAR), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), transpiration quotient (TQ) and SPAD chlorophyll meter reading (SCMR). All the physiological parameters except LGR between 35 and 75 DAS, TDM at 35 DAS and SCMR at 35 and 75 DAS had high heritability and moderate to high genetic advance implying that additive gene effects were mainly responsible for the expression of these characters. Seed yield/plant was positively and significantly correlated at phenotypic and genotypic levels with LAI, CGR and biological yield/plant. It had negative genotypic correlations of moderate strength (r=-0.599-(−) 0.394) with TQ at 35 and 75 DAS indicating its positive relationship with water use efficiency. Dry matter production, early growth and development of the crop are important under drought stress due to continuous decline in available soil moisture. Since LAI, LGR, CGR, RGR and NAR are the functions of dry matter production and/or leaf area, therefore, selection on the basis of high biological yield and large LAI at 50% flowering should be quite effective in improving seed yield under drought. An increase in LAI might increase radiation load resulting in to high transpiration. Therefore, genotypes having high LAI with erect leaves and low TQ should be accorded priority in the selection programme.