Morphological and Molecular Diversity of Colletotrichum gloeosporioides Causing Yam (Dioscorea alata L.) Anthracnose Disease in Côte d’Ivoire

Abstract

Yam is a plant of great importance for the Ivorian people in terms of food, nutrition, economy, and socio-cultural value. However, its production is threatened by several biotic factors, including anthracnose, one of the most destructive diseases affecting yams. The objective of this study was to assess the morphological and molecular diversity of Colletotrichum gloeosporioides isolates responsible for anthracnose in yam (Dioscorea alata) in Côte d'Ivoire. Twenty-seven previously isolated strains were collected from Plant Health Laboratory of Nangui ABROGOUA University and analyzed. The study examined the cultural (coloration, growth mode, texture, and colony diameter), microscopic (conidial shape, size, and spore concentration), and molecular characteristics of these isolates. Significant morphological diversity was observed among the isolates. Macroscopically, three major groups were identified based on colony coloration (whitish, orange, and grayish). Colony textures varied, presenting cottony, flaky, downy, or filamentous appearances, with growth patterns ranging from concentric and radiating to regular rings. Colony diameters ranged from 37 mm to 82 mm. Microscopically, sporulation varied significantly among isolates, ranging from 1.1 × 10⁵ to 85.4 × 10⁵ spores, as did conidial size, which ranged from 10.54 to 19.29 µm in length and 3.93 to 6.43 µm in diameter. Molecular analysis through comparison with GenBank nucleotide sequences revealed homology rates of 99-100% and varying proximities between the rDNA sequences of the isolates. In conclusion, the characterization of these isolates provides valuable insights for improving disease control strategies for yam anthracnose.