Abstract
Microorganisms (bacteria and fungi) were isolated from different parts of yellow maize (stem, cob, husk, leaf, root) as well as from rhizosphere and non-rhizosphere soil of maize using conventional microbiological techniques. A total number of twenty-six bacteria and thirteen fungi were isolated. The antagonistic efficacies of these isolates were tested against Sclerotium rolfsii, Aspergillus repens, Penicillium notatum and Pythium sp. using streak bioassay, food poisoning and dual culture techniques. None of the bacteria was antagonistic to the test fungi at 25°C on PDA using streak bioassay. However, there was reduction in the population density of the test fungi using food poisoning technique. The fungal isolates were antagonistic to the test fungi in varying degrees. Generally, S. rolfsii was susceptible to seven out of the eight fungal antagonists while P. notatum was least susceptible. The percentage reduction of S. rolfsii ranged from 40.00 ± 5.78 to 64.07 ± 2.31. Efficacies of chemical fungicides; mancozeb, camazeb and red force at 3 different concentrations— 0.05%, 0.1% and 1.0% (w/v) on the test fungi were also determined. No growth of the test fungi was observed at 1% (w/v) of all the fungicides while at lower concentration (0.05%), red force did not have any inhibitory effect. The growth of S. rolfsii was completely inhibited at 0.05% of mancozeb whereas there was reduction in mycelial growth of A. repens. Effect of inoculation time and nutrients (PDA and MEA) was determined on the antagonistic activities of Trichoderma viride. There were significant differences in inhibitory potentials of the two isolates of Trichoderma viride when pre-inoculated on the culture medium. The antagonistic potentials were more pronounced on malt extract agar than potato dextrose agar.
Highlights
Crops are usually affected by phytopathogenic fungi and fungal diseases are difficult to control without the use of synthetic fungicides [1]
It is well established that there are large and diverse numbers of bacteria found on plants and a diverse set of bacteria have been identified with biocontrol activities [5]
Thirteen fungal isolates were obtained from the samples and were identified as Thysonaphora longispora, Trichoderma species, Staphylotrichum sp., Aspergillus flavus, Stachylidium, Hirsutella saussurei, Hirsutella saussurei, Penicillium italicum, Gonatobotryum apiculatum, Trichoderma viride, Condropodium pseudotsugae and Aspergillus niger
Summary
Crops are usually affected by phytopathogenic fungi and fungal diseases are difficult to control without the use of synthetic fungicides [1]. The application of large quantities of chemicals in agriculture has the potential to exert toxic effects on humans and wildlife as well as to cause environmental pollution [2]. Increasing use of chemicals causes several negative effects, i.e., development of pathogen resistance to the applied agents and their non target environmental impacts [3]. Biological control treatment consisting of living microorganisms or abiotic products can provide disease protection essentially through one or more of the following: production of antibiotics or other molecules that are deleterious to the pathogen’s development, competition with the pathogen for nutrients and space or induced plant resistance [4]. The use of bacteria as biocontrol agents of foliar disease of cereals has been reported to be an alternative of great potential [6]. Studies on the use of maize associated microorganisms in Nigeria are not common, the present investigation is aimed at determining the antifungal potencies of maize associated microorganisms
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