Association of nitrogen use efficiency in diverse rice genotypes with sustenance of reproductive stage photoassmilation and nitrogen metabolism

To maintain yield stability and environmental sustainability of rice cultivation, improvement in nitrogen use efficiency (NUE) is essential. We identified rice genotypes showing high NUE in control (N120) and N deficient (N0) field conditions by analyzing NUE parameters and different contributing traits. In the first season, genotypes BAM-3181, BAM-4797, BAM-3154, NL-26 IR-83929-B-B-291-3-1-1 (IR-3-1-1), APO and NERICA-L-42 showed high biomass, panicle yield and N utilization efficiency (NutE) at low N field conditions. Reproductive stage N assimilatory and signaling gene expression was correlated to the variation in NUtE. The sequence variation in N metabolism and signaling (NLP) genes were analyzed in selected genotypes (APO and NERICA-L-42). Significant non-synonymous SNPs were found in NPF2.2, PTR2, NGR9 (DEP1), Fd-GOGAT, NLP3, NLP4 and NLP5 genes of APO, NERICA-L-42 and w.r.to japonica genotype Nipponbare. The significant variation in reproductive stage gene expression and changes in amino acid sequence of NLP3, NLP4, NLP5 among rice genotypes differing in NUE is an unexplored and potent genome editing target for high NUE in rice. The non-synonymous SNPs identified in the study will be important genomic resources for improving rice NUE.