No abstract

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.

Ascochyta blight (AB), caused by the fungal pathogen Ascochyta rabiei, is a devastating foliar disease of chickpea (Cicer arietinum L.). The genotyping-by-sequencing (GBS)-based approach was deployed for mapping QTLs associated with AB resistance in chickpea in two recombinant inbred line populations derived from two crosses (AB3279 derived from ILC 1929 × ILC 3279 and AB482 derived from ILC 1929 × ILC 482) and tested in six different environments. Twenty-one different genomic regions linked to AB resistance were identified in regions CalG02 and CalG04 in both populations AB3279 and AB482. These regions contain 1,118 SNPs significantly associated with AB resistance (p ≤ 0.001), which explained 11.2–39.3% of the phenotypic variation (PVE). Nine of the AB resistance-associated genomic regions were newly detected in this study, while twelve regions were known from previous AB studies. The proposed physical map narrows down AB resistance to consistent genomic regions identified across different environments. Gene ontology (GO) assigned these QTLs to 319 genes, many of which were associated with stress and disease resistance, and with most important genes belonging to resistance gene families such as leucine-rich repeat (LRR) and transcription factor families. Our results indicate that the flowering-associated gene GIGANTEA is a possible key factor in AB resistance in chickpea. The results have identified AB resistance-associated regions on the physical genetic map of chickpea and allowed for the identification of associated markers that will help in breeding of AB-resistant varieties.