Isolation and multidimensional characterization of Colletotrichum gloeosporioides (Penz. & Sacc.) associated with anthracnose in groundnut (Arachis hypogaea L.)

Groundnut (Arachis hypogaea L.) is most popularly called as the ‘King of oil seeds’ and it is a highly valued leguminous crop in India and worldwide. Groundnut productivity is declining due to multiple biotic and abiotic stresses that hinder effective cultivation and cause substantial yield losses. Anthracnose, a destructive fungal disease incited by Colletotrichum species, has become a significant threat to groundnut cultivation in key growing regions of Tamil Nadu. The disease manifests initially as small, water soaked and yellowish spots along the leaf margins, which progressively expand and develop into well defined, circular brown lesions with a distinct yellow halo. As the infection advances, extensive foliar damage occurs, ultimately leading to substantial yield losses. The disease, exacerbated by warm, dry conditions and airborne spores during the rainy season. This study investigated the morphological and growth characteristics of ten Colletotrichum gloeosporioides isolates collected from different locations. The isolates exhibited distinct variations in mycelial growth, colony pigmentation, zonation patterns and sporulation capacity. Notably, isolate Cg1 exhibited the highest mycelial growth. Morphologically, the isolates displayed diverse features, including a fluffy white appearance, cottony mycelium and variations in sporulation. Additionally, differences in conidial size and shape were noted. The pathogen exhibited optimal growth under a 12 hrs light and 12 hrs dark cycle, at a temperature range of 25-30 °C and a pH of 5.0. This study emphasizes the pivotal influence of morphological and physiological parameters influencing the development and growth of Colletotrichum gloeosporioides isolates.