Cultural and morphological variations of Didymella rabiei isolates causing chickpea ascochyta blight in northwestern Ethiopia

Abstract Chickpea ( Cicer arietinum L.) is one of the important grain legume crops in Ethiopia, which is used as a source of food and foreign currency. However, the crop production and productivity are currently challenged by ascochyta blight disease caused by Didymella rabiei in the study areas. Thus, this research was conducted to determine morphological and cultural characteristics of D. rabiei isolates collected from chickpea‐growing districts in northwestern Ethiopia during the 2022 cropping season. Twenty representative diseased chickpea samples were taken from 120 samples for morphological and cultural study of D. rabiei isolates. The isolates were arranged in a completely randomized design with three replications to record their cultural and morphological features. The results showed variations in colony color, growth pattern, colony diameter, and conidial size and shape. The analysis of variance revealed significant ( p  < 0.01) differences in conidia diameter, length, and width among studied isolates at 25°C incubation for 14 days. The mean conidia growth of the isolates varied from 2.33 cm (MDa isolate) to 7.13 cm (SFw isolate) on 9 days of measurement. Isolates ranged in conidial length and width from 1.32 to 6.17 µm and 1.23 to 5.31 µm, respectively. SFw and MDd isolates had the longest and shortest conidia dimensions, in that order. The majority of the isolates produced grayish‐white colony color on the front plate, non‐zonated colonies, and regular and whitish colony margins. Cluster analysis using cultural and morphological data showed variations in D. rabiei isolates by grouping them into seven distinct classes. Thus, the finding on the variability study of this pathogen is essential to develop management strategies, especially resistant varieties. To support this study, further molecular characterization of the genetic diversity of D. rabiei isolates is required.