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

Chickpea fields were surveyed in nine major chickpeagrowing
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.