Mapping the mating type locus of Ascochyta rabiei, the causal agent of ascochyta blight of chickpea.

SUMMARY A genome linkage map was developed for Ascochyta rabiei (Pass.) Labrousse, (teleomorph) Didymella rabiei (Kovachevski), an important pathogen causing ascochyta blight in chickpea (Cicer arietinum L.). The map was constructed using 96 progeny generated from a single pseudothecium produced from a cross between a USA MAT-2 isolate and an Australian MAT-1 isolate. The map comprised 126 molecular markers of which 69 were random amplified polymorphic DNA (RAPD) markers, 46 were amplified fragment length polymorphic (AFLP) markers, 10 were sequence-tagged microsatellite site (STMS) markers, and one was a sequence characterized amplified region (SCAR) marker. Eighteen large and 10 small linkage groups (LG) were characterized and the mating-type locus was mapped on to LGd. The map spanned 1271 cM with an average spacing between markers of 15.1 cM. The SCAR marker, specific for mating type 2, was designed to amplify a region of the MAT locus and was used to identify the mating type of A. rabiei isolates. One AFLP marker, derived from the MAT-1 parent, was closely linked to the mating-type locus (9.6 cM). The linkage map provides a framework for the future identification of the locations of other important traits such as virulence/avirulence and fungicide resistance. Findings from this study suggest that the MAT-2 isolates of D. rabiei should be renamed to MAT-1 isolates because the alpha-box, specific for MAT-1 from other ascomycetes, was amplified from A. rabiei MAT-2 isolates.