Genetic diversity and mating-type distribution of Didymella rabiei isolates collected from Kurdistan region, North of Iraq

Chickpea is considered as one of the most important sources of proteins in many developing countries including Iraq. Didymella rabiei, causing ascochyta blight disease on chickpea, is a destructive pathogen on chickpea in the north of the Iraq (Kurdistan region). Detailed knowledge about the genetic diversity and pathogenicity of the pathogens is necessary to adopt appropriate disease control and management strategies. For the purposes of this study, a combination of phenotypic and genotypic characterizations including simple sequence repeat (SSR) fingerprinting, mating-types distribution and pathogenicity analyses were used to assess a total of 145 D. rabiei isolates collected from chickpea fields in the Sulaymaniyah provincial region of northern Iraq in 2020. Our results revealed a relatively high level of genetic diversity (H = 0.66) within populations, with low differentiation among populations. These findings together with mating types which were found in a 50:50 ratio, suggest the role of sexual reproduction in the fungus, primarily as primary inoculums of D. rabiei which are likely ascospores (sexual spores). On the contrary, the existence of gene exchanges through either the movement of infected seeds or plant debris is most probably the main mechanism in reduction of differentiation among populations. Hence, the use of certified chickpea seeds and removing plant debris are recommended for effective management of the disease.