The degree of green rot severity was evaluated in two yam species, D. alata and D. cayennensis. The causal agent of this disease is the fungus Penicillium sclerotigenum, a highly virulent pathogen on D. cayennensis in the producing areas all over the world. In addition, by cross inoculation, an investigation was conducted on the occurrence of physiological adaptations of the fungus relative to its pathogenicity on these species of yams. To complement this study the mycelial growth of P. sclerotigenum was evaluated on three culture media, two based on extracts of the yam species examined and the other one on potato (Solanum tuberosum). Dextrose and agar were added to all cultures. The results showed that green rot was less severe on D. alata than on D. cayennensis. No physiological adaptation in relation to the pathogenicity of P. sclerotigenum to both yam species was found. Potato-dextrose-agar and D. cayennensis-dextrose-agar were the best substrates for P. sclerotigenum development and growth.
cross inoculation; pathogenic especialization; in vitro growth; Dioscorea alata; D. cayennensis
