Epiphytotics of chickpea Ascochyta blight in Turkey as influenced by climatic factors

Chickpea Ascochyta blight caused by Didymella rabiei is one of the most important fungal diseases affecting yield and seed quality negatively in Turkey. Breeding efforts against this devastating disease fail as the resistance/tolerance is broken in a short period of their commercial cultivation. This study was aimed to determine the status of Ascochyta blight epiphytotics and the effect of climatic factors on the disease incidence and severity in Turkey. Chickpea fields were surveyed for disease prevalence and severity in forty-five major chickpea-growing provinces in 9 climatic regions in the cropping season 2014, 2015, and 2016 in Turkey. The data on major weather parameters, i.e., rainfall (mm), air temperature (oC) and relative humidity (%), were procured from Ministry of Agriculture and Forestry, Turkey, and correlations among disease severity, altitude, weed density, nodule numbers, and climatic conditions were calculated. Principal component analysis was studied to determine the complex effects of all the variables on Ascochyta disease severity. It was observed that there was significant difference in percent incidence and severity of Ascochyta blight among the 45 provinces representing nine agro-climatic regions during the period under study. The highest disease incidence and severity (%) were recorded in Bosporus, Black Sea, Aegean and Mediterranean regions, while it was the lowest in Eastern Anatolia and Southeastern Anatolia. Negative correlation was recorded between disease severity and altitude and temperature, and that relative humidity (%) and rainfall (mm) showed statistically positive correlation with the disease severity. The disease severity was not effected by nodule numbers and weed density ratios.