Markers associated with Ascochyta blight resistance in chickpea and their potential in marker-assisted selection

A chickpea recombinant inbred line (RIL) population F6:7 was evaluated for disease reaction to blight caused by Ascochyta rabiei in three different environments. In Spain, disease was measured in the field by the area under the disease progress curve (AUDPC) and in the greenhouse by the linear infection index (LII). In Tunisia, disease was measured in the field by the 1–9 scale of Reddy and Singh [Plant Dis. 68 (1984) 900]. Twenty RILs showing extreme values for resistance and susceptibility were selected from field and greenhouse data obtained in Spain and assessed individually for DNA markers linked with disease resistance. Previously, 1028 DNA markers were found polymorphic in a collection of resistant and susceptible accessions of chickpea and 39 of them were associated with resistance. Both the more resistant and the more susceptible RILs, evaluated in Spain, were scored for the 39 chosen markers and 20 of them maintained a clear association with resistance or susceptibility. These loci formed a linkage group covering a map distance of 18.8 cM when the entire RIL population (n=76) was analysed. The markers on the linkage group were significantly associated with disease reaction in the three environments, indicating the presence of a QTL for resistance to blight in this genomic region and explaining from 20 to 23.7% of the total phenotypic variation of the character. The resistant genotype for random amplified polymorphic DNA (RAPD) marker OPAC04/1200, in the middle of the group, was the most frequent (84%) in a set of cultivars and breeding lines selected as resistant to Ascochyta blight. The association of the other markers with resistance on each side of OPAC04/1200 decreased in frequency inversely with their distance from this locus. This result suggests that the QTL for resistance to blight would be close to OPAC04/1200 and we therefore propose to use this marker jointly with two others (OPAI09/1276 and OPM02/935) that flank it in MAS.