Mating type distribution and incidence of the teleomorph of Ascochyta rabiei (Didymella rabiei) in Canada

Chickpea (Cicer arietinum L.) acreage has increased rapidly in western Canada since 1995, and Ascochyta rabiei (Pass.) Labr. is the most important pathogen of this new crop. Wind-borne ascospores produced by the teleomorph play an important role in disease spread and pathogen survival in many regions. The teleomorph stage, however, has not been reported in Canada. Mating-type assessments of 42 isolates from 34 fields in Saskatchewan were conducted using tester isolates. The two mating types occurred at similar frequencies across the region. Over-wintered chickpea residue was collected in April of 1999 and 2000. The teleomorph was detected on the: residue by microscopic dissection and by two methods of ascospore discharge, one using a novel and inexpensive apparatus. Mature ascospores were found at six of seven sites in 1999. No ascospores were found in material from 13 sites in 2000. However, asci were found later in the season in a separate study conducted at one site. The occurrence of the teleomorph stage in the onion may increase field-to-field spread of ascochyta blight of chickpea and contribute to increased genetic variability of the pathogen in western Canada.