Pathogenicity Variation Among Phytophthora infestans Isolates Collected from Potato Fields Across Different Agroclimatic Zones

Abstract

Late blight of potato, caused by Phytophthora infestans, remains one of the most destructive plant diseases worldwide, leading to severe yield losses under conducive environmental conditions. Understanding pathogenic variability among pathogen populations is essential for effective disease forecasting and resistance breeding. The present study evaluated pathogenicity variation among P. infestans isolates collected from potato fields across different agroclimatic zones. Infected leaf samples exhibiting characteristic late blight symptoms were collected, and pathogen isolates were obtained using standard isolation techniques. Pathogenicity assays were conducted on susceptible potato cultivars under controlled conditions to assess differences in aggressiveness, lesion development, incubation period, and disease progression among isolates. The results revealed significant variation in pathogenicity among isolates originating from different agroclimatic regions, indicating the presence of highly diverse and adaptable pathogen populations. Certain isolates exhibited rapid lesion expansion, shorter incubation periods, and higher disease severity, while others showed comparatively reduced virulence. These differences suggest variability in genetic makeup and adaptive potential of P. infestans populations influenced by environmental conditions and host selection pressure. Agroclimatic factors such as temperature and humidity were found to play a key role in shaping pathogen aggressiveness and disease expression. The observed pathogenic diversity highlights the evolutionary potential of P. infestans and its ability to overcome host resistance under favorable conditions. The findings provide valuable insights into the epidemiology of late blight and emphasize the need for region-specific disease management strategies. This study supports the development of integrated approaches, including resistant cultivars and timely fungicide applications, for sustainable potato production.