Assessment of reproductive stage drought tolerance using stress indices in improved restorer lines of KMR-3R in rice

Drought stress during the reproductive stage is an evident limitation of rice grain yield. The present study aimed to assess the reproductive stage drought tolerance of eight promising backcross inbred lines (BILs) with complete fertility restoration in the genetic background of KMR-3R. Various stress indices based on grain yield under Non-stress (NS) and drought-stress (DS) conditions were used to assess BILs drought tolerance potential. Based on correlation analysis, the best indices for determining drought-tolerant genotypes were K2STI, YI, HM, SNPI, GMP, and DTI. By ensuring stable performance, the indices K2STI and YI were crucial criteria in identifying DS genotypes. The stress-tolerant and susceptible genotypes were best differentiated under DS using the susceptible indices TOL and ATI, which had considerably low values. The IL-1, IL-2, and IL-7 (RP6340-NRR-5, RP6340-NRR-11, and RP 6340-NPVR-25) were identified as promising drought-tolerant genotypes based on lower grain yield reduction under DS. The improved restorers with drought tolerance performed well under DS in terms of agronomy, and it may be exploited in hybridization programs to develop elite drought-tolerant rice hybrids for unfavorable ecologies.