Crop Protection & Environmental Biology

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Author: search.filters.author.Dania, V. O

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    Allelopathic potential of some biocontrol agents for the control of fungal rot of yellow yam (Dioscorea cayenensis Lam)
    (2015) Dania, V. O; Fadina, O.O; Ayodele, M..; Kumar, P. L.
    The adverse effects of synthetic pesticides on human health and 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 paring method was used for the in vivo trials. The destruction 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 theobromate, 14.0 + 0.33% with Penicillium oxalicum, 7.1 + 0.14% when paired with Rhizoctonia solani: 17.1 + 0.11% with Sclerotium rolfisii, 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 distant zone of inhibition, especially by the bacterial antagonist 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
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    Efficacy of Oryza sativa husk and Quercus phillyraeoides extracts for the in vitro and in vivo control of fungal rot disease of white yam (Dioscorea rotundata Poir)
    (Springer Plus, 2014) Dania, V. O; Fadina, O.O; Ayodele, M; Kumar, P L
    Tuber rot disease is a major constraint to white yam (Dioscorea rotundata) production, accounting for 50-60% of annual yield losses in Nigeria. The main method of control using synthetic fungicides is being discouraged due to human and environmental health hazards. The potential of Oryza sativa husk (OSH) and Quercus phillyraeoides (QP) extracts for the in vitro and in vivo control of six virulent rot-causing fungal pathogens, Lasiodiplodia theobromae, Aspergillus niger, Rhizoctonia solani, Penicillium oxalicum, Sclerotium rolfsii, and Fusarium oxysporum was evaluated, using five different extract concentrations of 0.5%, 1.0%, 1.5%, 2.5%, and 3.5% w/v. These fungi were isolated from rotted tubers of D. rotundata, across three agroecological zones in Nigeria—the Humid rainforest, Derived savanna, and southern Guinea savanna. All treatments were subjected to three methods of inoculation 48 hours before the application of both extracts and stored at 28 ± 2°C for 6 months. Radial mycelial growth of the test pathogens was effectively inhibited at concentrations < 3.5% w/v in vitro for both OSH and QP extracts. Rotting was significantly reduced (P < 0.05) to between 0 to 18.8% and 0% to 20.9% for OSH and QP extracts respectively. The extracts significantly (P < 0.05) inhibited percent rot of the test pathogens at 3.5% concentration w/v in vivo. Rot incidence was, however, lower in replicate tubers that were inoculated, treated with extracts and exposed than treatments that were covered. Phytochemical analysis of OSH and QP extracts revealed the presence of secondary metabolites such as alkaloids, flavonoids, saponins, tannins, ferulic acid, phlobatanins, Terpenoids, phenols, anthraquinone and pyroligneous acid. The efficacy of both extracts in reducing rot in this study recommends their development as prospective biopesticide formulation and use in the management of post-harvest rot of yam tubers.