Physiological and genetic regulation of seasonal biological nitrogen fixation in peanut for sustainable crop production

Biological nitrogen fixation is an important component of peanut productivity and soil-nitrogen cycling, yet it is commonly evaluated using measurements taken at individual growth stages rather than as an integrated and season-long trait. This review examines season-long biological nitrogen fixation in peanut as a dynamic process influenced by genotype, rhizobial effectiveness, soil nitrogen availability, water status, temperature, and crop developmental stage. We synthesize current knowledge of the physiological regulation of fixation, including carbon allocation to nodules, oxygen diffusion, nitrogenase activity, nitrogen transport, and feedback inhibition under high soil nitrogen. We also evaluate the complementary contributions of stable-isotope methods, nodulation traits, physiological indicators, and high-throughput phenotyping for characterizing fixation across time and environments. Genomic resources, including quantitative trait locus mapping, multi-parent advanced generation inter-cross populations, telomere-to-telomere reference genomes, multi-omics, and genomic selection, provide complementary opportunities to identify candidate loci and predict fixation-related performance. However, direct evidence linking peanut MAGIC populations and genomic prediction models specifically to season-long biological nitrogen fixation remains limited, and the transfer of detected QTL into breeding programs is constrained by moderate heritability, genotype-by-environment interaction, and methodological variation among studies. We propose a breeding framework in which season-long fixation is measured through standardized longitudinal phenotyping and evaluated jointly with yield, quality, stress tolerance, and nitrogen-use efficiency. Addressing these gaps will require coordinated studies integrating peanut genotypes, rhizobial partners, soil conditions, multi-environment trials, and genomic data. Such an approach could support the development of peanut cultivars that contribute more reliably to sustainable and climate-resilient cropping systems. Peanut is an important food and oil crop. It can obtain nitrogen from the atmosphere with the help of beneficial soil bacteria. This process is called biological nitrogen fixation and can reduce the need for nitrogen fertilizer. However, nitrogen fixation changes during the growing season and is affected by the peanut variety and environmental conditions. This review explains how nitrogen fixation changes throughout the peanut growing season. It also discusses how genetic tools, multi-parent populations, and plant measurements can help to identify peanut varieties with strong and stable nitrogen fixation. These approaches may help breeders to develop peanut varieties that perform well under changing environmental conditions.