Epidemiological studies and comprehensive screening of cercospora leaf spot of pigeonpea (Cajanus cajan L.) caused by Cercospora cajani Henn.

Pigeonpea (Cajanus cajan L.) is a vital pulse crop in India, but its productivity is severely impacted by various pests and diseases. Among these, Cercospora leaf spot (CLS) disease, caused by Cercospora cajani Henn., has emerged as a significant challenge to pigeonpea cultivation. A field study was conducted during the kharif season of 2023–24 at the experimental research farm of Tirhut College of Agriculture, Dholi, Muzaffarpur to evaluate the resistance of 114 pigeonpea genotypes, including a susceptible check, under artificial field conditions using an infector row technique. Based on percent disease index (PDI), 11 genotypes were moderately resistant, while 7 genotypes were moderately susceptible. On the basis of the area under disease progress curve (AUDPC), the same 11 genotypes were classified as resistance, whereas the 7 moderately susceptible genotypes were classified as moderately resistant. Significant differences in disease severity and AUDPC values were observed, suggesting varying levels of resistance among the genotypes. Furthermore, disease progression of CLS in pigeonpea was significantly influenced by weather conditions, with early-sown crops showing lower severity than late-sown crops. Maximum disease progression occurred from the first to second week of December under moderate temperatures (25.6–27.8 °C maximum and 14.0–18.5 °C minimum), high relative humidity, low wind velocity, light rainfall and limited sunshine. The regression models explained 77–91 % of the variation in disease severity. These findings contribute to identifying resistant pigeonpea genotypes and understanding environmental influences on CLS disease, thereby aiding future breeding programs for the development of disease-resistant varieties.