MOLECULAR ANALYSIS FOR TRAITS RELATED TO DROUGHT ADAPTATION IN RICE (Oryza sativa L.)
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Date
2023
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Abstract
Drought is a major abiotic constraint for rice production worldwide. Model based studies revealed reproductive stage drought stress (RSDS) and intermittent drought stress (IMDS) are expected to reduce yield significantly in Sali and Ahu season, respectively. The present study was conducted with the aim to detect the genetic effects of water stress through quantitative trait locus (QTLs) associated with drought tolerance in rice. The donor and the recipient parent were selected based on the phenotypic evaluation and gene expression analysis using five drought responsive genes in two drought tolerant cultivar (ARC10372, Koimurali) and two susceptible cultivar (Disang, IR-64). Based on the results, Koimurali was crossed with a drought susceptible cultivar, Disang to obtained true F1 seeds. Subsequently the single F1 seeds was selfed for and advanced to subsequent generations (F5:6) using single seed descent (SSD) method to develop the mapping population consisting of 247 RILs. Parental polymorphism study was conducted by screening 600 SSR markers; among which 98 SSR markers were found to be polymorphic (16.33%). The RILs along with their parents were genotyped using the 98 polymorphic SSR markers and a linkage map was constructed covering a distance of 2495.31cM spanning across the 12 linkage groups using the software JoinMap 4.0. The phenotyping score of two different stress condition (reproductive stage drought stress stress and intermittent drought stress condition) were compared with the genotypic data for identification of QTLs. The QTL analysis detected eight QTLs at reproductive drought stress located on chromosome number 3(qGY3LOD 3.54, qYSI3LOD3.54); 4(qGY4LOD 2.57, qTOL4 LOD 2.56, qYSI4 LOD 2.56, qYSI4 LOD 2.59, qRYR4 LOD 2.58, qDSI4, LOD 2.62) and 11 QTLs at intermittent drought stress located on chromosome1 (qFLW1, LOD 2.23, qNOC1 LOD 2.7, qNOG1 LOD 1.83); 3(GLW3 LOD 2.55), 4(qGY4 LOD 2.7, qRYR4 LOD 2.35, qTOL4 LOD 3.5, qTOL4 LOD 2.2, qYSI4 LOD 2.35), 7(qNOG7 LOD 2.91, qTNG7 LOD 2.84). The detected QTL regions were scanned to identify putative genes associated with drought tolerance in rice in both the stress conditions. The putative gene in reproductive drought stress were used to check the expression in four extreme breeding line of different drought tolerant capacities. QTL comparision between both the stress conditions were evaluated and one QTL was found common and few shared the same chromosome but in different marker intervals indicating different genetics might control the underlying stress conditions. The putative QTLs and candidate genes identified in the present study need to be further validated, which will be helpful for the improvement of drought tolerance in rice.