Assessing potato cultivars for resistance against late blight under high altitudinal conditions of North Western Himalayas

Different stages in plant development significantly influence the incidence of potato late blight disease in India. In the present study, the disease progression was monitored weekly in five selected potato cultivars viz. Kufri Jyoti, Kufri Giriraj, Gulmarg Special, Shalimar Potato-I, and Gurez local, during the 2018 and 2019 cropping seasons. The severity of potato late blight, caused by Phytophthora infestans, increased with fluctuations in weather variables. Calculations for the area under the disease progress curve (AUDPC) and the rate of disease spread (r-value) at different growth stages of potatoes were used to track disease progression. Notably, the Kufri Jyoti cultivar demonstrated resistance compared to the other cultivars, with lower severity values and susceptibility scale values (48.40%; 5.6 and 4.9) in 2018 and 2019, respectively. The average rate of disease progress was also lower in Kufri Jyoti (0.064 and 0.060) compared to the local cultivar (0.076 and 0.074) in 2018 and 2019, respectively. These observations indicate that weather parameters have a strong positive impact on the incidence of potato late blight.