Allelopathic potential of some biocontrol agents for the control of fungal rot of yellow yam (Dioscorea cayenensis Lam)

Abstract

The adverse effect of synthetic pesticides on human health and the natural ecosystem necessitate the need to explore natural mechanisms of disease control in plants. This study evaluated the allelopathic potential of five biocontrol agents: Trichoderma longibrachiatum, Trichoderma asperellum, Bacillus subtilis, Bacillus cereus and Pseudomonas fluorescens in the control of six fungal pathogens associated with tuber rot of Dioscorea cayenensis. Rotten tuber samples were randomly collected across three agro-ecological zones (AEZs): humid rainforest (HF), derived savanna (DS), and southern Guinea savanna (SGS) in Nigeria. Biocontrol agents were isolated from the yam rhizosphere using the serial dilution method; the agar pairing method was used for the in vitro trials. The destructive sampling method was used to evaluate rot control by the antagonists in vivo. Aspergillus niger had the highest incidence of 64.71% across the HF, 52.08% across the DS, and 41.98% across the SGS. B. subtilis had the highest inhibitory zone of 16.7 ± 0.05% when paired with A. niger, 15.4 ± 0.01% with Lasiodiplodia theobromae, 14.0 ± 0.33% with Penicillium oxalicum, 7.1 ± 0.14% when paired with Rhizoctonia solani; 17.1 ± 0.11% with Sclerotium rolfsii, and 10.3 ± 0.94% with Fusarium oxysporum. All biocontrol agents significantly (P = 0.05) reduced rot development of the test pathogens relative to the control in the in vivo experiment. The establishment of a distinct zone of inhibition, especially by the bacterial antagonists attests to the fact that they produced allelochemical substances. Therefore, further research is recommended to evaluate the biochemical composition of these microbial metabolites, their level of toxicity, and fate in the environment.

Efficacy of Moringa Oleifera Extract, Trichoderma Asperellum, A Synthetic Fungicide and Cattle Dung Amendment in The Integrated Management of Rice Blast Disease

“…The leaves were surfacesterilized with 10% sodium hypochlorite for one minute, rinsed in three changes of sterile distilled water and blot-dried on sterile filter paper before plating on PDA. The inoculated plates were incubated at 28 ± 2 o C for 4 days (Dania et al, 2015).…”

“…Spores were counted by dispensing 0.1 ml of inoculum on a hemacytometer. Spore concentration was adjusted to 10 6 spore/ml according to Dania et al (2015) and healthy rice plants with fully developed first four leaves were inoculated at 21 days. Plants inoculated with M. oryzae without any amendment served as control, while inoculated plants treated with Blastforce fungicide only served as positive check.…”

Antifungal Activities of Selected Plant Extracts in In-Vitro Control of Anthracnose and Root Rot Diseases on Cucumber (Cucumis sativus B.)

“…The experiment was carried out according to Dania, Fadina, Ayodele, and Kumar (2015) using, completely randomized design, replicated five times. Planting pots with the dimension 21.5 cm x 27 cm were filled with 7 kg of sterilized soil; three seeds of each variety of cucumber were sown in each pot and later thinned to 2 seedlings per pot.…”