Mating type distribution using a multiplex PCR mating assay and fertility status in Didymella rabiei in chickpea-growing areas in Iran

Abstract

Ascochyta blight, caused by Ascochyta rabiei is the most destructive disease of aerial parts of chickpea (Cicer arietinum L.) worldwide. Forty isolates of A. rabiei representing eight geographical regions, were collected from the west and south western Iran, and analysed for mating type distribution and fertility. A multiplex PCR assay using specific primers designed to amplify partial regions of the MAT1–1 and MAT1–2 idiomorphs was used to facilitate population analysis. Didymella rabiei populations were dominated by MAT1–1 mating type. The fertility status of isolates was determined using controlled crosses in vitro, pairing each isolate with compatible standard testers (USDA-AR-20 and USDA-AR21). Out of the 40 tested isolates, 38 isolates (95%) were MAT1–1 and two isolates (5%) were MAT1–2. Both mating types were present in Gachsaran and Jalian Populations, where Chi-square tests showed the proportions of each mating type were significantly different from 1:1 ratio. The predominance of one mating type in populations indicates that sexual reproduction is rare or may not occur with significant frequency in D. rabiei populations associated with chickpea in Iran. Microscopic studies of naturally infected tissues and inoculated with standard testers, which had been kept for two years under natural conditions, revealed the development of pseudothecia.

Keywords:

• A. rabiei
• C. arietinum
• chickpea
• D. rabiei
• mating type

Acknowledgments

We are grateful to Dr W.J Kaiser (USDA-ARS, Washington State University, Pullman, USA), for providing us the tester isolates MAT1-1 (ATCC 76501) and MAT1-2 (ATCC 76502).