The magnitude of Ascochyta blight of chickpea and its relationship with prevailing environmental conditions in the Thal region of Punjab, Pakistan

This study assessed Ascochyta blight disease in chickpea across five districts in the ‘Thal’ region of Punjab, Pakistan: Bhakkar, Jhang, Layyah, Muzaffargarh, and Mianwali. The disease prevalence, incidence, and severity were recorded over two consecutive years, 2020-2021 and 2021-2022, during the chickpea-growing season. Disease prevalence ranged from 76% in Layyah to 40% in Muzaffargarh. Layyah also exhibited the highest disease incidence (84.2%) and severity (59.41%), while Muzaffargarh recorded the lowest disease incidence (20.55%) and severity (8.55%). All thirty-seven fungal isolates obtained from diseased samples were morphologically identified as Ascochyta rabiei. Twenty-five isolates, including five representatives from each district, were characterized based on their pathogenicity. The isolate ARL1 from Layyah exhibited the highest pathogenicity, with disease rating scores of 8.5 in detached leaf assays and 7.3 in attached leaf assays. Pathogen virulence showed a positive relationship with the disease intensity observed in the respective districts. Disease incidence and severity were further correlated with various prevailing environmental factors in these districts. Disease incidence was positively correlated with relative humidity and wind speed, while disease severity showed a positive correlation with relative humidity and rainfall but a negative correlation with maximum temperature. Other epidemiological factors did not exhibit significant relationships with the disease. This study concludes that the ‘Thal’ region is highly threatened by Ascochyta blight disease due to relatively higher relative humidity, rainfall, wind speed, and fungal virulence. Therefore, proper and timely management practices are essential to mitigate the impact of Ascochyta blight disease and address these influencing factors effectively.