Modi, Mahendra KumarCHANDRAKANT, KALDATE RAHUL2023-12-122023-12-122021https://krishikosh.egranth.ac.in/handle/1/5810202719Drought is a major abiotic constraint for rice production worldwide. The reproductive stage drought stress (RSDS) leads to a huge loss in grain yield. The prospecting of new donor cultivars with identification and introgression of large effect drought tolerance related QTLs is essential to develop drought-tolerant rice varieties. The present study was conducted with the aim of mapping quantitative trait locus (QTLs) associated with drought tolerance in rice. With a total of 3417 GBS (Genotyping by sequencing) based polymorphic SNP (Single nucleotide polymorphism) markers distributed over the rice chromosomes a saturated linkage map spanning 1924.136 cM was constructed with an average marker density of 0.56 cM using an F3 mapping population developed by crossing traditional Ahu rice cultivar Koniahu (drought tolerant) with Disang (drought susceptible). Using inclusive composite interval mapping (ICIM) approach 172 genomic regions associated with grain yield and related traits were detected in 198 F3 and F4 segregating lines evaluated for two consecutive seasons under both RSDS and irrigated control conditions. Of which, 102 QTLs were identified under RSDS with LOD (Logarithm of odds) score value ranging between 2.53 to 7.51 and phenotypic variance explained (PVE) value of 1.97 to 12.42 per cent. While 70 QTLs with LOD score value ranging between 2.50 to 10.07 and PVE value of 2.35 to 11.46 per cent were detected under control condition. In total, nine QTLs were major QTLs having a PVE value 10. Among the QTLs identified under RSDS, 72 (70.59%) QTLs were novel whereas 30 (29.41%) QTLs were observed to be co-localized or overlapped with genomic regions previously mapped for the same trait/ QTLs. Five putative QTLs namely, qGY2.00, qGY5.05, qGY6.16, qGY9.19, qGY10.20 were found to be associated with grain yield under drought. Further, fourteen CAPS (Cleaved Amplified Polymorphic Sequences) were developed from selected eight novel QTLs linked SNP regions and validated in parental cultivars along with ten F5 generation RILs. Putative gene identification within eight QTL regions detected a total of 3341 genes in which 1516 (45.63%) genes were annotated to at least one gene ontology (GO) term. 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.EnglishThesis