Main effect QTLs associated with arsenic phyto-toxicity tolerance at seedling stage in rice (Oryza sativa L.)

Arsenic phyto-toxicity is a limiting factor affecting rice production in the Indo-Gangetic flood plain. In this study, 98 microsatellite markers were used to map quantitative trait loci (QTL) conferring arsenic phyto-toxicity tolerance (AsT) at seedling stage from a F-2 population derived from a cross between an arsenic sensitive indica rice cultivar (BRRI dhan45) and an arsenic tolerant indica rice cultivar (BRRI dhan47) using selective genotyping technique. Arsenic phyto-toxicity tolerance of F-2:3 population was assessed with an arsenic stress of 1.25 mg L-1 under hydroponic culture in a climate chamber. AsT indices for shoot length, root length and root-shoot biomass were estimated in terms of comparative growth in treated plants compared to that in control plants. A total of four main effect QTLs with significant LOD comprising two for relative growth in shoot length, one for each of root length and root-shoot biomass under arsenic stress were identified on chromosomes 8 and 12 using composite interval mapping approach. A large effect QTL for arsenic phyto-toxicity tolerance in root length contributing 24.9 % phenotypic variation was identified on chromosome 8 with plausible pleiotropic effect on shoot length and root-shoot biomass.