Effects of nutritional and environmental factors on growth and antagonistic activities of three Aspergillus species against cocoa black pod organism (Phytophthora palmivora)

Abstract

In vitro screening was undertaken to assess the effects of nutritional and environmental factors on the potential of three isolates of Aspergillus namely Aspergillus fumigatus, A. repens, and A. niger as biological control agents against the cocoa black pod pathogen, Phytophthora palmivora. Nitrogen and carbon sources were the nutritional factors tested while temperature and pH were the environmental factors evaluated. This study was carried out in the Department of Plant Biology of the University of Ilorin, Nigeria between 2009 and 2010. The test antagonists were the incubated under different conditions and their activities against the pathogen recorded. Results revealed that the nutritional fsctors were essential for inoculum biomass production as well as for sustaining biological activities of the test antagonists. Antagonistic activities of the test organisms were expressed over a range of temperatures (15-35˚C) but were best expressed at 30˚C. Antagonistic activities dropped outside this range under the conditions of this study. Strong inhibition of the cocoa pathogen by the test organisms was observed between the pH 5 and 6.5. It can be cocoa black pod pathogen. The aim of this study was to investigate the effect of environmental ad nutritional factors on the potential of Aspergillus fumigatus, A. repens and A. niger to suppress the growth of Phytophthora palmivora.