Expression of putative anthracnose stalk rot resistance genes in tropical maize germplasm

ABSTRACT Colletotrichum graminicola (Ces.) G. W. Wilson is the causal agent of anthracnose stalk rot (ASR), an important disease in maize (Zea mays L.). This pathogen colonizes and degrades the vascular tissues of the stalk, resulting in premature plant death and significant yield losses. Genetic control of resistance is determined by a few genes, with additive effects being the predominant mode of inheritance. This study examined the expression of genes related with maize defense against C. graminicola, using contrasting inbred lines for resistance to ASR in tropical germplasm, through reverse transcription quantitative polymerase chain reaction (RT-qPCR). Gene expression analysis was conducted on eight occasions post-inoculation for eight genes involved in the defense response, including those encoding pathogenesis-related proteins, secondary metabolites, and phytohormones. We observed difference in the expression of defense genes between the resistant (L04-2) and susceptible (L99-4) lines. L04-2 line exhibited a rapid and intense defense response, characterized by the early induction and sustained expression of defense genes. Results indicate that the resistance of L04-2 is primarily associated with the early and significant induction of the LOX5 gene, which encodes for lipoxygenases, enzymes that catalyze the oxygenation of polyunsaturated fatty acids, leading to the formation of oxylipins. These molecules regulate the biosynthesis of jasmonic acid, a phytohormone that is directly involved in the activation of various defense genes. The scientific findings can help in the development of maize cultivars with higher resistance to ASR.