Aus rice: a source of promising donor genotypes for low N tolerance under field conditions

) for two wet seasons (2021 and 2022) and one dry season (2022). Data was recorded for seven traits viz., single plant grain yield (SPGY), single plant biomass yield (SPBY), single plant straw yield (SPSY), plant height (PH), tiller number (TN), SPAD chlorophyll meter readings (SCMR) and days to 50% flowering (DFF). Existence of wide genotypic variability was noticed not only for SPGY, but also for SPBY, SPSY, PH, TN, SCMR and DFF. Heat map clustering categorized the low N tolerant genotypes and grouped SPGY, SPBY and SPSY as sensitive traits to low N. M202 noted as highly tolerant to low N in wet season but was intermediate in dry season, indicating variable response of the genotype with season. Improved varieties viz., IR64-21, M202, BINA Dhan 5, BRRI Dhan 47 found to be tolerant to low N and can be immediately used in NUE breeding programmes.