Genome-wide association study for bacterial leaf streak resistance in maize

Maize (Zea mays L.), one of the most important crops worldwide, is affected by foliar diseases that limit its global production. Bacterial diseases have increased in Argentina during the last years. The aim of this work was to explore a maize panel provided by the International Maize and Wheat Improvement Center (CIMMYT) to identify alleles associated with resistance to bacterial leaf streak (BLS) of maize, a disease caused by Xanthomonas vasicola pv. vasculorum, in central Argentina. A diverse panel of 200 maize lines was evaluated for resistance to bacterial diseases in four environments of central Argentina in 2020 and 2021. The predictor of the genetic merit does not include environmental effects and 46,990 single-nucleotide polymorphisms obtained by genotyping-by-sequencing were used in the genome-wide association study (GWAS). The 10 lines with the lowest severity across environments belonged to different environmental adaptation programs defined by CIMMYT. The GWAS allowed us to identify 11 genomic regions associated with BLS, located in chromosomes 1, 2, 5, 7, 8, and 9. Five of those regions, located in bins 1.04, 2.01, 5.03, 8.06, and 9.03, were associated with plant defense candidate genes such as strictosidine synthase-like 11, protein-serine/threonine phosphatase, and a putative Leucine-Rich repeats receptor-like serine/threonine-protein kinase gene. Our study provides potential resistance alleles to BLS that can be incorporated to improve maize breeding programs.