Quantitative Trait Loci Associated with Anthracnose Resistance in Sorghum

Sorghum [Sorghum bicolor (L.) Moench] is highly susceptible to the fungal disease anthracnose, which is a major biotic constraint to forage and grain production. With an aim to develop durable resistance to anthracnose,, two unique genetic sources of resistance in sorghum were selected to create genetic mapping populations and identify genomic regions that control anthracnose resistance. A series of quantitative trait loci (QTL) were identified that conferred variable levels of resistance, three of which controlled stable resistance across all environments, while two QTL were environment specific. A major anthracnose-resistance QTL on chromosome 9 of the SC155-14E genome was observed in all environments and controlled from 19 to 62% of the phenotypic variance. An additional major QTL on chromosome 5 of the SC414-12E genome explained from 20 to 39% of the phenotypic variance and was observed in four of the six environments tested. Resequencing of the genomes of resistant cultivars SC155-14E and SC414-12E facilitated a preliminary survey of the coding regions of genes annotated as playing a role in host defense. The resequenced genomes of the resistant genotypes and the linkage mapping resources represent information relevant for more detailed molecular characterization of genes conditioning anthracnose resistance in this tropical cereal. The identification of QTL conferring anthracnose resistance and the identification of single-nucleotide polymorphisms linked to these loci will provide the necessary molecular tools for markerassisted introgression of durable anthracnose resistance into elite sorghum inbreds.