Pathotype-specific genetic factors in chickpea (Cicer arietinum L.) for quantitative resistance to ascochyta blight

Ascochyta blight in chickpea ( Cicer arietinum L.) is a devastating fungal disease caused by the necrotrophic pathogen, Ascochyta rabiei (Pass.) Lab. To elucidate the genetic mechanism of pathotype-dependent blight resistance in chickpea, F(7)-derived recombinant inbred lines (RILs) from the intraspecific cross of PI 359075(1) (blight susceptible) x FLIP84-92C(2) (blight resistant) were inoculated with pathotypes I and II of A. rabiei. The pattern of blight resistance in the RIL population varied depending on the pathotype of A. rabiei. Using the same RIL population, an intraspecific genetic linkage map comprising 53 sequence-tagged microsatellite site markers was constructed. A quantitative trait locus (QTL) for resistance to pathotype II of A. rabiei and two QTLs for resistance to pathotype I were identified on linkage group (LG)4A and LG2+6, respectively. A putative single gene designated as Ar19 (or Ar21d) could explain the majority of quantitative resistance to pathotype I. Ar19 (or Ar21d) appeared to be required for resistance to both pathotypes of A. rabiei, and the additional QTL on LG4A conferred resistance to pathotype II of A. rabiei. Further molecular genetic approach is needed to identify individual qualitative blight resistance genes and their interaction for pathotype-dependent blight resistance in chickpea.