QTLs for ascochyta blight resistance in faba bean (Vicia faba L.): validation in field and controlled conditions

Ascochyta blight is an important disease of faba bean (Vicia faba L.). Yield losses can be as high as 90% and losses of 35–40% are common. The line 29H is one of the most resistant accessions to the pathogen (Ascochyta fabae Speg.) ever described. In this work, we aimed to validate across generations the main quantitative trait loci (QTLs) for ascochyta blight resistance identified in the cross 29H × Vf136 and to test their stability under field conditions. QTLs located on chromosomes II and III have been consistently identified in the recombinant inbred line (RIL) population of this cross, in both controlled (growth chamber) and field conditions and, thus they are good targets for breeding. In addition, a new QTL for disease severity on pods has been located on chromosome VI, but in this case, further validation is still required. A synteny-based approach was used to compare our results with previous QTL works dealing with this pathogen. Our results suggest that the QTL located on chromosome II, named Af2, is the same one reported by other researchers, although it is likely that the donors of resistance differ in the allele conferring the resistance. By contrast, the location of Af3 on chromosome III does not overlap with the position of Af1 reported by other authors, suggesting that Af3 may be an additional source of resistance to ascochyta blight.