GENETIC BASIS OF VARIATION FOR SALINITY TOLERANCE IN OKRA (Abelmoschus esculentus L.)

Abstract

For the development of salinity tolerant okra breeding material, studies were undertaken on the assessment of genetic variability for salinity tolerance in the available okra germplasm at the seedling stage, assessment of genetic diversity with molecular makers, responses of the selected tolerant and non-tolerant genotypes to salinity stress during ontogeny of the whole plant in summer and spring seasons and genetic basis of variation for salinity tolerance. Substantial variation appeared to exist in okra for salinity tolerance at the seedling stage. The 80 mM NaCl concentration was found suitable for discriminating tolerant and non tolerant okra genotypes because many genotypes failed to germinate at higher NaCl concentrations and maximum variation among the genotypes appeared at this concentration. The pooled ranking of the genotypes, based on their individual rankings for each trait in single NaCl concentration appeared effective for selecting tolerant genotypes. Twenty RAPD primers were used to analyze the genetic diversity among the okra germplasm, which showed considerable polymorphism in the okra genotypes. The cluster analysis divided the 39 okra genotypes into seven main clusters with maximum similarity of 82.88% between Sabzpari 2001 and Acc.No.019221. The genotypes selected at the seedling stage for salinity tolerance maintained their tolerance to NaCl during the ontogeny of whole plant. This suggested that the screening of the germplasm accessions and breeding material for salt tolerance at the seedling stage is effective, at least for initial selection. The NCM II analysis was carried out to estimate components of genetic variation in okra genotypes. The inheritance of salinity tolerance in okra at seedling stage appeared to be governed by both additive and non additive genetic effects. The additive effects were predominant and narrow sense heritability was moderate. It is concluded that the genetic variation for tolerance to NaCl salinity existed among the okra genotypes, which had considerable heritable component and, therefore, genetic improvement of okra genotypes for salinity tolerance through breeding and recurrent selection is possible.