Evaluation of drought tolerance and marker-trait association of selected rice varieties using morpho-physiological, biochemical and molecular approaches

Drought is a main stress factor for rice yields, causing substantial economic losses, and climate change is intensifying its impact. Meanwhile, Myanmar is one of the most climate-vulnerable countries in the world, with agriculture facing significant challenges. In this study, to determine the osmotic stress response of rice varieties in Myanmar under drought conditions, 16 rice varieties were screened hydroponically using 15-20% polyethylene glycol 6000 at the seedling stage. After 14 days of treatment, morpho-physiological and biochemical parameters of rice were recorded. Based on the Drought Resistant Index derived from plant growth parameters and IRRI SES score, we were able to classify that rice varieties STK, ST-STL, LTH, NMTL, MNTK, AYPDT, PTY, STY and Yar8 were categorized as drought tolerant genotypes, while YZLT, PSBK, Y90, Yar9, IR64 and DL17 were identified as moderately drought tolerant genotypes. SAKR3 was found to be drought-susceptible. The genetic diversity of 16 rice varieties using 34 SSR markers related to drought traits flanking over 12 rice chromosomes detected a total of 100 alleles with the average polymorphic information content (PIC) value of 0.43 while RM481 showed the highest PIC value of 0.68. Cluster analysis using UPGMA divided the rice varieties into two distinct groups: one comprising PSBK and NMTL and the other containing the remaining 14 varieties. A total of 15 SSR markers were significantly associated with 11 morpho-physiological and biochemical traits at a P-value of < 0.05 while only 7 SSR markers were related with 5 traits at a P-value of < 0.01. These findings will support breeders and researchers in developing new drought tolerant rice varieties and in identifying new QTLs across various chromosome regions.