Population dynamics and aggressiveness of fungal pathogens associated with chilli root rot

Chilli (Capsicum annum L.) is one of the most important vegetable crops worldwide and root rot disease is a significant threat to its production. This study documented the disease prevalence, incidence, and severity of root rot, as well as identified the aggressiveness of fungal and oomycetes microbial communities associated with this disease in chilli growing districts of Punjab, Pakistan. In 2020-21, a field survey was conducted in nine different districts and disease samples were collected from symptomatic chilli fields. Of the 112 fields visited, 73 were found with symptomatic root rot infection. The risk of disease prevalence, severity, and incidence was highest in Lahore 87.5%, 69%, and 64.14% respectively, while the lowest disease prevalence, incidence, and severity were recorded in district Bahawalnagar 16.67%, 14.8%, and 17% respectively. It is concluded that, the disease prevalence, incidence, and severity level of the disease is higher in Lahore compared to other chilli growing areas of Punjab, Pakistan. A total of fifteen fungal colonies were isolated and categorized into two different groups: A=Pathogenic, and B=Non-Pathogenic based on the frequency of detection and pathogenic status. The pathogenicity and aggressiveness of group-A isolates were tested on the highly susceptible chilli variety 'Desi', and it was concluded that P. capsici and R. solani cause the highest incidence and severity of root rot. Three different culture media (PDA, MEA, and PARP) were used for isolation, and it was observed that all fungal and oomycetes were easily isolated on PDA media, and the percentage frequency on PDA media was also maximum as compared to MEA and PARP media. However, to our knowledge, this is the first study to explore and measure the aggressiveness of fungal and oomycete pathogens for root rot of chilli in the Punjab region of Pakistan and the first to systematically evaluate various cultural media for detection of pathogens associated with this problem. (author)