Nitrogen dose dependent changes in leaf greenness, crop phenology, grain nitrogen content and yield in rice (Oryza sativa L.) sub-species

In the present study, 30 diverse genotypes of rice sub-species were evaluated for variations in phenology, grain protein content, grain morphology and yield under field conditions with different nitrogen (N) regimes i.e., N deficient (N=0) and N sufficient (N=120 kg ha⁻¹). N deficiency decreased the leaf greenness, panicle yield, grain protein content, altered the grain morphology and grain-related parameters. Significant variations in grain morphology-related parameters such as grain length and grain width among rice genotypes were observed for different N treatments. Changes in grain morphology related parameters were correlated with yield. The study identified Sahbhagi Dhan, BAM-759, BVD-109, Pusa Sugandh-5, and Kalinga-1 that maintained higher vegetative greenness, while Sahbhagi Dhan, Vandana, Nerica-L-44, Kalinga-1 and APO that showed higher panicle yield under N0 condition. Rice genotypes APO, Nerica-L-42 and Kalinga-1 performed well under N0 with a lesser impact on crop phenology and grain morphology. Grain protein content was found higher in BAM-759, Anjali, Thurur Bhog, IR-64, Rasi, and Kalinga-1under both the treatments. Flag leaf Soil Plant Analysis Development (SPAD) and Normalized Difference Vegetation Index (NDVI) measurements were significantly correlated with grain yield, and grain protein content. The trait specific donors suitable for low N conditions identified in the study will pave the way forward to the research in understanding underlying mechanisms and in crop improvement programs.