Chickpea Ascochyta Blight: Disease Status and Pathogen Mating TypeDistribution in Syria

摘要

Chickpea fields were surveyed in nine major chickpeagrowingprovinces of Syria in 2008 and 2009 to determinethe prevalence and severity of Ascochyta blight,and the distribution of Didymella rabiei mating types(MATs) in the country. A total of 133 Ascochyta rabieiisolates were assayed for mating type, including isolatesfrom older collections that date back to 1982.Multiplex MAT-specific PCR with three primers wasused for MAT analysis. Out of the 133 tested isolates,64% were MAT1-1 and 36% were MAT1-2. BothMATs were found in six provinces but MAT1-1 alonewas found in three provinces. Chi-squared analysiswas used to test for a 1 : 1 ratio of MAT frequenciesin all samples. The MAT ratios in the six provinceswere not significantly different from 1 : 1, suggestingthat there is random mating of the pathogen populationunder natural conditions. The presence of the twoMATs is expected to play a role in the evolution ofnovel virulence genes that could threaten currentlyresistant chickpea varieties. Overall analysis of the 133isolates showed a significant deviation from the 1 : 1ratio with almost twice as many MAT1-1 isolates thanMAT1-2 isolates, which indicates a competitive advantageassociated with MAT1-1 in Syria. However, theoverall picture of an unequal frequency in MATs indicatesthat there may be limited sexual recombinationoccurring in the Syrian population.