Fitness Evaluation of Phytophthora infestans Isolates Collected from Punjab, Pakistan During 2017-18

Potato late blight (Phytophthora infestans) is an important disease causing severe damage in potato crop worldwide. Seventy seven isolates of P. infestans selected on the basis of aggressiveness were characterized for pathogen fitness test based on their lesion size, latent incubation period and sporulation capacity after their inoculation onto detached leaves of potato. The results showed that large variations in pathogen fitness were present among isolates for each regional P. infestans population studied. Those isolates selected during 2017-18 exhibited 85% and 74% successful pathogen fitness behavior respectively. Those isolates which had higher composite fitness index values were observed higher lesion size and spore count and same trend of pathogen fitness parameters was observed with respect to their districts during both the years.This is the first inclusive study to determine pathogen fitness of isolates in Pakistan. The experimental findings indicated that population of P. infestans in the Punjab province comprises diverse isolates with low to high fitness potential. A future challenge planned to combine our accumulated knowledge with that from other scientific fields to develop a disease management approach for late blight.