Influence of metabolites of Aspergillus niger van Tieghem on chlamydospores formation by Phythophthora palmivora (Butl.) causing black pod disease of cocoa [Theobroma cacao].
1996
Annang T.Y. | Odamtten G.T.
Chlamydospores of Phytophthora palmivora may survive in cocoa farm soil and serve as source of inoculum for black pod disease epigytotics. Culture filtrate of Aspergillus niger raised on V-8 broth at 35deg C for 4 days was used to assess influence of the metabolites of A. niger on chlamydospore formation by P. palmivora on Oatmeal agar. Commercial fungicides used by farmers for the control of P. palmivora namely Kocide, Ridomil, Champion and Caocobre were also tested for their efficacy in preventing in-vitro chlamydospore formation by P. palmivora. All concentrations (recommended field application rate- 1/10 recommended rates) of the test fungicides prevented chlamydospore formation on oatmeal agar by P. palmivora; so did the undiluted and 1:1v/v dilutions of A. niger culture filtrate. Further dilutions (1:2 -1:200v/v dilutions) of A niger culture filtrate permitted varying degrees of chlamydospores formation resulting in varying sizes (diameter 16.0-48.0micro m) and thickness (o.6-4.8micro m) of investing walls. The effects produced by oxalic acid (concentration of 2.0-7.0 x 105M), one of the components of the metabolites of A. niger was same as A. nigher metabolites.
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