S G Desai

Tobacco (Nicotiana tabacum L.) is a key non-food crop of the Solanaceae family, valued globally for its leaves. It significantly contributes to revenue, export earnings, and employment. Major producers include China, India, the USA, and Brazil. India ranks second, producing 12.3% of global tobacco, with cultivation concentrated in states like Andhra Pradesh, Gujarat, and Karnataka. Gujarat ranks second in area (1.74 lakh ha) and production (5.19 lakh tons), primarily in districts like Anand, Kheda, and Mehsana. Damping-off, caused by P. aphanidermatum, is a critical nursery disease. Studies (2019-2021) revealed variability in pathogen isolates, cultural and molecular characteristics, and management strategies. Seventeen isolates were identified, with hydroponic inoculation being the quickest method for proving pathogenicity. Morphological variability included differences in mycelium and oospore size. Molecular studies showed genetic diversity, with isolates clustering into two groups. In vitro studies of nine fungicides showed azoxystrobin, metalaxyl combinations, and others achieving 100% inhibition, while Bacillus subtilis provided the highest biocontrol efficacy (64.16%).

This research investigates the pathogenic variability of Pythium aphanidermatum and its impact on tobacco (Nicotiana tabacum L.) cultivation, specifically bidi tobacco, a major cash crop of Gujarat, India. Key findings include the isolation and identification of 15 pathogenic isolates from infected soil, with Pa4 and Pa14 isolates showing the highest virulence, causing up to 98% seedling mortality. Screening across 28 wild Nicotiana species and tobacco varieties revealed varying resistance, with ABT 10 and Anand 2 being relatively more resilient, while no variety was entirely resistant. Biochemical analysis showed that higher phenol and lower sugar content were associated with increased resistance. Fungicide efficacy trials in nursery conditions identified metalaxyl M + mancozeb, azoxystrobin + difenoconazole, and benalaxyl-M + mancozeb as the most effective treatments. Organic inputs like Panchagavya (5%) were moderately effective in inhibiting the pathogen's growth. The findings highlight the need for integrated management practices and resistant varieties to mitigate damping-off disease, thereby supporting sustainable bidi tobacco production in Gujarat..