Morphological and Molecular Diversity of Traditional Upland Rice (Oryza sativa L.) Varieties for Drought Tolerance at Seedling Stage

Drought is considered the major threat and most damaging abiotic stress for rice production.However, some traditional upland rice varieties (TURVs) may have some forms of tolerance to various stresses compared to new elite varieties. Two experiments were conducted. Experiment to determine the morpho-physiological response, phenotypic diversity, and similarity of 13 TURVs and 2 check varieties to mild drought stress at the seedling stage (Experiment 1 (E1) and to determine the molecular diversity and genetic similarity of the genotypes using selected simple sequence repeat (SSR) markers ((Experiment 2 (E2). In E1, all TURVs were highly tolerant under mild drought stress for a physiological response. Standardized Shannon-Weaver Diversity Index(H’) showed zero to low phenotypic diversity for qualitative traits. However, the phenotypic diversity of quantitative traits ranged from moderate to high for well-watered conditions, low to high for drought conditions, and moderate to high for re-watered conditions. Cluster analysis through Ward’s minimum variance based on pooled phenotypic data grouped the genotypes into three major clusters at 7 Euclidean distances. For E2, polymorphic information content values from 24 polymorphic SSR markers ranged from slightly informative (RM256) to highly informative (RM206), with a mean of 0.61. Nei’s gene diversity mean was 0.62 and values varied from 0.26 (RM256) to 0.86 (RM206). Based on Jaccard’s similarity coefficient, rice genotypes were grouped into nine minor clusters. The results indicate that TURVs harbor moderate to high allelic diversity and there are potential tolerance genes for mild drought stress that can be utilized in breeding programs for drought-tolerant rice varieties.