Genome-wide association study reveals cytochrome P450 associated with post- emergence metribuzin tolerance in soybean (Glycine max)

Abstract Soybean (Glycine max) is one of the most important crops in the world. However, due to multiple herbicide resistance in weeds, few effective postemergence herbicide options remain to control weeds in soybean production systems. Metribuzin is currently one of the most promising herbicides for managing weeds in soybeans due to the low frequency of developing resistant populations. Currently, metribuzin is applied as a pre-emergent herbicide because post-emergence applications are thought to excessively damage most soybean varieties. In this study, a panel of 196 genetically diverse accessions in maturity groups 4, 5, and 6 was used to identify genomic regions associated with soybean response to metribuzin as well as metribuzin-tolerant accessions. Two different concentrations (150 g ai ha⁻ ¹ and 300 g ai ha⁻ ¹) of metribuzin were sprayed across two experimental replications, each with three replicates. A total of nine SNP markers were identified as significantly associated with soybean response to metribuzin. These SNPs are linked to Cytochrome P450 superfamily proteins (CYP), exocyst complex components, and ethylene-responsive transcription factor 3. These candidate genes indicate metabolism is likely the dominant mechanism of tolerance with the management of oxidative stress as a secondary mechanism. Together, these findings reveal novel candidate genes and pathways associated with non-target site resistance and provide valuable markers for breeding soybean cultivars with improved post-emergence metribuzin tolerance.