Elucidation of genetic architecture for aphid resistance in alfalfa (Medicago sativa) via genome-wide association study.

BACKGROUND: Aphids that feed on alfalfa (Medicago sativa) are widespread pests, causing significant losses in yield and forage quality through direct feeding damage and the transmission of plant viruses. In this study, we assessed aphid resistance in 239 genetically diverse alfalfa accessions across multiple field environments by quantifying aphid infestation levels. RESULTS: Leveraging more than 1.9 million high-quality single nucleotide polymorphisms, a genome-wide association study identified 22 genomic loci significantly associated with aphid resistance. These loci were distributed across all eight alfalfa chromosomes and collectively explained between 4.05% and 24.19% of the observed phenotypic variance. Functional annotation of the candidate genes revealed their involvement in key biological pathways, including ubiquitin-mediated proteolysis, ABC transporter activity, and immune signaling processes. Notably, two NLR-type resistance genes, Msa.H.0143490 and Msa.H.0461950, emerged as strong candidates for enhancing aphid resistance through genetic improvement. CONCLUSIONS: These findings provide valuable insights into the genetic architecture of aphid resistance and offer molecular markers that can be utilized in marker-assisted selection to develop more resilient alfalfa cultivars.