Chickpea Ascochyta Blight: Disease Status and Pathogen Mating Type Distribution in Syria

摘要

Chickpea fields were surveyed in nine major chickpea-growing provinces of Syria in 2008 and 2009 to determine the prevalence and severity of Ascochyta blight, and the distribution of Didymella rabiei mating types (MATs) in the country. A total of 133 Ascochyta rabiei isolates were assayed for mating type, including isolates from older collections that date back to 1982. Multiplex MAT-specific PCR with three primers was used for MAT analysis. Out of the 133 tested isolates, 64% were MAT1-1 and 36% were MAT1-2. Both MATs were found in six provinces but MAT1-1 alone was found in three provinces. Chi-squared analysis was used to test for a 1 : 1 ratio of MAT frequencies in all samples. The MAT ratios in the six provinces were not significantly different from 1 : 1, suggesting that there is random mating of the pathogen population under natural conditions. The presence of the two MATs is expected to play a role in the evolution of novel virulence genes that could threaten currently resistant chickpea varieties. Overall analysis of the 133 isolates showed a significant deviation from the 1 : 1 ratio with almost twice as many MAT1-1 isolates than MAT1-2 isolates, which indicates a competitive advantage associated with MAT1-1 in Syria. However, the overall picture of an unequal frequency in MATs indicates that there may be limited sexual recombination occurring in the Syrian population.