Screening Rice (Oryza sativa L.) Genotypes for Seedling-Stage Drought Tolerance

Abstract

Drought stress is a major abiotic constraint to rice productivity. Seedling-stage screening of rice genotypes is therefore essential for identifying key adaptive traits and drought-tolerant genotypes. This study evaluated 40 lowland rainfed rice genotypes for seedling-stage drought tolerance under greenhouse conditions using a split-plot randomized complete block design. Progressive drought stress was imposed for 21 days, and root and shoot traits were assessed. Substantial morphological variability was observed among genotypes for most traits. Drought stress significantly reduced root dry weight (52.8%), shoot dry weight (51.6%), seedling biomass (51.5%), number of roots (39.3%), number of roots with at least 5 cm length (37%), and shoot length (21.1%). Root-to-shoot ratio showed significant water × genotype interaction. Correlation analysis, heritability, and genetic advance identified root traits as reliable selection criteria for seedling-stage drought stress screening. Combined Drought Stress Response Index (CDSRI) classified 17.5% of genotypes as tolerant and 12.5% as sensitive. Tolerant genotypes (B1P15, Chupa, Mucabo, Mpulo, Nasoco, Nene, and Mutanzania) represent a valuable resource for rice breeding targeting early-season drought resilience. These findings support breeders in identification of adaptive traits and provide a basis for policy interventions to invest in drought-resilient varieties that benefit farmers in rainfed areas.