Exploring arsenic (As) tolerant and exclusion donors for use in rice (Oryza sativa L.) breeding

Abstract

Growing rice under arsenic (As) stress inevitably invites a huge risk of As exposure to humans and livestock in Asian countries. Identification of As-tolerant rice genotype(s) with accumulation of As in straw and grains below the threshold limit can be a way forward to mitigate such a life-threatening problem. The present study systematically evaluated 131 diverse rice genotypes for As tolerance based on germination and seedling growth parameters and selected a few elite As tolerant genotypes at appropriate lethal (LD50). The rice genotypes responded differentially with marked differences in tolerance under As stress. Exposure to As adversely affected germination and seedling growth. Significantly higher estimates of relative seedling vigor index and both stress tolerance indices and relative tolerance indices are coherently associated with tolerant rice genotypes with no symptoms of damage on leaves. A major proportion of As uptake was shown to be retained in roots in tolerant genotypes with a progressive decrease in the order of leaf sheath> leaf blade> husk> kernel under As stress, although the extent of partitioning was genotype-specific, signifying As exclusion in shoot and grains. The first Principal component alone explained 78.16% of the total phenotypic variation. Seedling tolerance indices, vigor indices and germination percentage were shown to be important criteria for As tolerance based on PCA and correlation analysis. PCA biplot revealed highly As tolerant genotypes, e.g., Ashutosh, BRRI Dhan-72, CST Sel. 4, Mahanadi, MI 156, OR(CZ) 78-1, PB-1, Pusa Sugandha 3 and Pusa Sugandha 3-1 with higher positive score value on 1st Principal Component. The As-tolerant genotypes identified in this pursuit would certainly help in planning As tolerance breeding in rice.