Evaluating breeding and management solutions for methionine content in soybean.

Soybean is widely recognized as a valuable crop and plant protein source due to its ideal amino acid profile. However, deficient methionine content in soybean seeds limits the nutritional utility. Therefore, a genome-wide association study (GWAS) utilizing 311 soybean accessions from maturity groups IV and V was performed alongside genomic prediction models to determine genetic underpinnings and breeding potential. Additionally, sulfur fertilization source and rate were evaluated for their impact on methionine content in soybean seeds. Across four environments, 23 novel single nucleotide polymorphisms (SNPs) were identified as being associated with methionine content, and average prediction accuracy (r2) ranged from 0.03 to 0.62 for genomic prediction models. Across six locations, soybean plots treated with ammonium sulfate (AMS) exhibited statistically increased methionine content when compared to other sulfur fertilizers. When combined, these results highlight the complex genetic and environmental controls for methionine content in soybean seeds and will positively contribute to protein quality improvement in soybean.