Inhibitory Potentials of Trichoderma harzianum and Two Botanicals against Fungi Associated with Postharvest Rots of Ipomoea batatas (L.) Lam

Abstract

The mycoparasitic potentials of Trichoderma harzianum, and growth inhibitory effects of Vernonia amygdalina (bitterleaf) and Zingiber officinale (ginger) on rot fungi in Ipomoea batata were examined. Rotting tubers were collected from Agbowo, Ojoo and Bodija markets in Ibadan. They were taken to the laboratory under sterile conditions. Different concentrations of the plants’ extracts and spore suspensions of T. harzianum were prepared. The fungi isolated from the rotting tubers were later cultured on plates impregnated with different concentrations of the extracts and T. harzianum. Incubation was done at 28ºC for 14 days. Data collection was done at 24 hours interval. The fungi isolated were Aspergillus niger and Rhizopus stolonifer. T. harzianum at 1 x 10-3 had a significantly (p≤ 0.05) better pathogens’ inhibition than 1 x 10-5. Inoculation of T. harzianum before the pathogens gave total inhibition. Inhibition of A. niger was significantly (p≤ 0.05) higher than R. stolonifer. Plant extracts from ethanol gave significantly (p≤ 0.05) better pathogens’ inhibitions than that from distilled water. Extracts from both plants gave significantly (p≤ 0.05) better growth inhibition than control. Growth inhibition was significantly (p≤ 0.05) higher at absolute concentration of both extracts than other concentrations. Extract from ginger gave significantly (p≤ 0.05) better inhibition than that from bitter leaf. F-values for model (P> 0.0001) and concentrations (P> 0.0024) for the T. harzianum were highly significant. F-values for model (P> 0.0001), concentration (P>0.0001) and treatment (P>0.0001) for the plants extracts were also highly significant. The results further underscore the mycoparasitic potentials of T. harzianum as well as growth inhibitory effects of Z. officinale and V. amygdalina on fungi rot pathogens of Ipomoea batata.