Morphological and physiological characterization of Colletotrichum gossypii and C. dematium infecting Cotton (Gossypium spp.)

A detailed investigation was conducted to characterize the principal fungal agents responsible for cotton anthracnose, Colletotrichum gossypii and Colletotrichum dematium. Comprehensive morphological analyses revealed that C. gossypii is distinguished by cylindrical conidia (14.25-19.00 × 2.7-5.03 μm) and flexible setae, while C. dematium produces falcate conidia (18-24 × 2.5-3.5 μm) and rigid, melanized setae. Both species exhibited optimal growth on potato dextrose agar (PDA) at 25-30°C and pH 5.5-6.5. Physiological studies demonstrated that temperature and pH strongly influence fungal proliferation, with significant growth inhibition observed outside these optimal ranges. Pathogenicity assays highlighted that C. gossypii induces boll rot and ramulosis (witch’s broom), whereas C. dematium causes necrotic leaf spots and dry boll rot. The study establishes a robust framework for the identification and characterization of these pathogens, emphasizing the importance of environmental conditions and morphological traits in understanding anthracnose epidemiology in cotton.