Potentiel Antifongique de Trichoderma Contre Rhizopus stolonifer Agent Responsable de la Pourriture Post Récolte de l’Igname (Dioscorea rotundata)

Postharvest rot generated by Rhizopus stolonifer is a key issue that restricts the healthy development of yam industry. To compensate for this deterioration, farmers rely mainly on chemicals. However, theses not only cause environmental pollution, but also increase the amount of pesticide residues in agricultural products, which is potentially harmful to human health and capable of inducing the appearance of resistant microorganisms. In the face of these adverse effects, research of beneficial microorganisms such as Trichoderma is a biological alternative to resolve the problem. The antagonism test was carried out in vitro by dual culture and by antibiosis (cellophane membrane). In situ tests were conducted by direct inoculation of Trichoderma sporal solutions at different concentrations (105 to 107 conidia/ml) on yam discs. In vitro, T. harzianum A (IT12) and Trichoderma sp. (E2) inhibited radial growth of Rhizopus stolonifer respectively from 42.11±0.00 to 44.08±0.66 for pair culture and 100±0.00 for antibiosis. The inhibition observed during different test is explained by the fact that Trichoderma can produce enzymes and antimicrobial secondary metabolites. In situ, their sporal suspensions in a curative test reduced necrosis diameters to 107conidia/ml from 15±0.00 and induced total protection in a preventive test. Trichoderma harzanium (IT12) and Trichoderma sp. (E2) have been shown to be effective in conserving yam tubers against R. stolonifer, significantly reducing mycelial growth and necrosis diameter on the tuber. To do this, they could be used as an alternative to control the pathogens responsible for the rot of the yam in stock.

KEYWORDS: Dioscorea rotundata, Rhizopus stolonifer, postharvest rot, Trichoderma spp., Biological alternative.