Role of sexual reproduction in the aggressiveness of Didymella rabiei affecting chickpea

Chickpea production is affected by Ascochyta blight disease in many countries and popular cultivars are put out of production due to the evolution of highly aggressive pathogen population. Sexual reproduction is believed to play an important role in the evolution of aggressive population in Didymella rabiei. Three crosses were made using four parental isolates (AR01 as MAT1-2 and AR02, AR03 and AR04 as MAT1-1) with varying levels of aggressiveness collected from Syria. Twenty randomly selected progenies per cross together with their
respective parents were tested on susceptible (ILC-263) and resistant (ICC-12004) chickpea genotypes for their aggressiveness. Moreover, the
mating type frequency was determined using multiplex Mating type markers. Latent period and disease severity were used to measure isolate
aggressiveness in the progenies. The mean latent period ranged from 6-12 days in all progenies. The progenies showed significant differences on their aggressiveness in the three crosses. High level of aggressiveness of the progenies was generated from AR01 by AR04 crosses. The frequency of the two mating types was almost equal in all crosses. Our findings showed that sexual reproduction can create progenies that can adapt to resistant cultivars and could affect the effectiveness of commonly used fungicides to manage Ascochyta blight.