Estudo de associação genômica ampla no melhoramento genético de milho para resistência a doenças

Abstract

Maize (Zea mays L.) is one of the main agricultural crops in Brazil, with significant economic and social importance. However, diseases such as red and pale stunting, white spot, and southern corn leaf blight can severely compromise productivity, especially under conditions favorable to the development of pathogens or vectors. The use of genotypes with genetic resistance is an effective and sustainable strategy for managing these diseases. In this context, the present study aimed to conduct a genome-wide association study (GWAS) with 292 maize inbred lines, in order to identify potential genomic regions associated with responses to infections caused by red and pale stunting, white spot, and southern corn leaf blight. Field trials were carried out during the 2023 and 2024 growing seasons at GDM Genética do Brasil, in Cambé-PR, with phenotypic evaluations based on disease severity scales. Genotyping of the lines was performed using the high-density Illumina Maize 25K XT Infinium Array, containing 23,908 single nucleotide polymorphisms (SNPs). After obtaining the genotypic data, quality filters were applied using the ASRgwas package, excluding SNPs with a minor allele frequency (MAF) below 5% and markers or samples with a call rate below 90%. The genome-wide association analysis was also conducted using the ASRgwas package, employing the False Discovery Rate (FDR) method to reduce false positives. SNPs with an adjusted p-value below 0.05 were considered significant. Four SNPs significantly associated with susceptibility to stunting diseases were identified, located on chromosomes 2, 9, and 10. These markers explained approximately 14% of the observed phenotypic variation. No field occurrence of white spot or southern corn leaf blight was recorded. The results contribute to the identification of candidate genomic regions that may be explored in marker-assisted selection strategies in maize breeding programs. Continued studies with additional evaluations across more years, environments, and growing conditions are necessary to validate the identified regions, ensure the consistency of the observed associations, and enable the discovery of new genomic regions related to disease resistance, thereby expanding the genetic base available for the management of the target diseases.