Morpho-agronomic Characterization, Genetic Diversity, and Saltol QTL Retention in Mutagenized Doubled Haploid Pokkali Lines
Abstract
A combined strategy of anther culture-derived doubled haploidy and gamma irradiation was employed to enhance the agronomic performance of the salt-tolerant rice cultivar Pokkali, which is traditionally constrained by tall stature, late maturity, and poor plant architecture. Seven doubled-haploid (DH) lines were subjected to 250 Gy ^60Co gamma irradiation, generating approximately 14,000 mutant plants. Through multi-generation field evaluation (M2–M5), ten elite mutant lines were selected and comprehensively characterized using morpho-agronomic traits, seedling-stage salinity screening, and molecular markers. Phenotypic evaluation revealed substantial improvements in key agronomic traits, with mutants flowering 6–18 d earlier and maturing 11–23 d earlier than the wild type. Plant height was significantly reduced by 24.7–43.8% (38–67 cm), accompanied by a 26.6–49.0% reduction in culm length, resulting in improved lodging resistance and plant architecture. Yield-contributing traits were also enhanced, with 70% of mutant lines exhibiting longer panicles (up to a 4-cm increase) and spikelet number per panicle increasing by 4–44% relative to Pokkali. Grain morphology was favorably altered, with 50% of the mutants showing a 26–48% increase in decorticated grain shape ratio. Genetic diversity analysis using 106 SSR markers revealed polymorphism among the mutants, confirming mutation-induced genomic variation. Salt tolerance screening and QTL analysis demonstrated that several elite mutants retained the Saltol QTL, whereas others showed allelic modifications, indicating novel genetic variation for salinity response. Overall, the integration of induced mutagenesis and DH technology proved highly effective in generating genetically stable rice lines with improved maturity, plant architecture, yield components, and retained or modified salinity tolerance, offering valuable genetic resources for saline-prone rice ecosystems.