A quantitative-trait locus for resistance to ascochyta blight [Ascochyta lentis] maps close to a gene for resistance to anthracnose [Colletotrichum truncatum] in lentil

Ascochyta blight, caused by Ascochyta lentis, is an important disease of lentil causing serious yield and quality losses. The objectives of the present research were to investigate the genetics of resistance to ascochyta blight, using a population of recombinant inbred lines (RILs) developed from a cross between the susceptible Lens culinaris 'Eston' and a resistant germplasm line (PI 320937), and to identify markers associated with resistance to ascochyta blight, using a quantitative-trait loci (QTLs) analysis. The RILs were spray-inoculated with an isolate of A. lentis (3C-2) in a replicated greenhouse test. The RILs scores for reaction to ascochyta blight showed a continuous distribution, suggesting a polygenic inheritance of resistance to ascochyta blight in lentil. A QTL that explained 41% of the variation in the reaction to ascochyta blight was identified on the linkage-group 6. This QTL was localized between an amplified fragment length polymorphism (AFLP) marker (ctcaccB) and LCt2, a gene for resistance to anthracnose [Colletotrichum truncatum]. This is the first evidence in lentil for linkage between genes conferring resistance to two different foliar pathogens. The result was further verified by cosegregation of a marker locus (OP-P4400) in our mapping population, which was also previously identified to be linked to a major QTL for resistance to ascochyta blight in the lentil germplasm line ILL-5588. The AFLP and random amplified polymorphic DNA (RAPD) markers localized around the resistance region will be useful tools in marker-assisted selection.