Genetic mapping of Ascochyta blight resistance in an ILL6002 × Indianhead lentil mapping population

Ascochyta blight of lentil (Lens culinaris Medik.) is a fungal disease caused by Ascochyta lentis. This study was carried out to identify the location of quantitative trait loci (QTL) associated with resistance from the accession Indianhead, and how these vary between the recently identified pathotypes of A. lentis. We performed QTL mapping using F₆ recombinant inbred lines derived from a cross between the resistant cultivar Indianhead and susceptible accession ILL6002, following evaluation in seedling assays and the field. Phenotyping identified nine QTL across the four different isolates. A major QTL effective against Pathotype 1 isolates was identified on chromosome 2 in both the seedling and field phenotyping, explaining 60.5% and 12.6% of the resistance phenotype, respectively. Additional QTL for resistance associated with Pathotype 1 isolates were identified on chromosomes 3, 5, and 7, explaining between 8.5% and 13.1% of the phenotype. In contrast, QTL associated with resistance to Pathotype 2 isolates were identified on chromosomes 1, 2, 3, and 7, in locations distinct from those associated with Pathotype 1 resistance. These loci explained between 8.8% and 29.6% of the phenotypic variation. Additionally, evaluation of a natural powdery mildew infection revealed a major QTL on chromosome 3, explaining 25% of the resistance phenotype. The markers flanking the loci identified herein will allow for lentil breeding programs to trace the associated resistance in their breeding program pedigree.