The potential of endophetic non-pathogenic fusarium oxysporum (schlecht: fries) to control radopholus similis in tissue culture banana
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The use of endophytic non-pathogenic Fusarium oxysporum (Schlecht.: Fries) strains in the control of Radopholus similis (Cobb) Thorne in tissue culture banana is a new biological control strategy being investigated at the International Institute of Tropical Agriculture - Uganda. This strategy, unlike other nematode management strategies, involves use of an antagonist, fungal endophyte, which is commonly present and inhabits the banana tissues where the nematode feeds. The fungal endophyte strains used were previously isolated from rhizome tissues of healthy banana plants grown in nematode infested fields, preserved on soil tubes under laboratory conditions and rejuvenated by growing on media under laboratory conditions. These fungal endophyte strains readily colonize and persist in the tissues of tissue culture plantlets, the best pest- free banana planting material recommended for use in nematode management. The study was structured in form of three experiments, with the first experiment focusing on the testing of F.oxysporum strains, V5w2 and III4w1 on R. similis multiplication in Enyeru (Musa sp. AAA-EA), Kibuzi (AAA-EA), Gros Michel (AAA), Valery (AAA) and Kayinja (ABB) banana cultivars. The total number of R. similis inside the root tissues of inoculated plants was numerically lowered in the above cultivars. The second experiment that investigated the effect of a simultaneous inoculation with multiple F.oxysporum strains on R. similis multiplication in Enyeru plants indicated lower population densities of R. similis in root tissues of inoculated plants. A ‘cock tail’ of three strains (Eny 1.31i, V5w2 and V4w5) was observed to have a greater influence on the nematode numbers than those involving two strains. The final experiment that centred on the effect of the F.oxysporum strain, V5w2, on two different population densities of R.similis (500 Rs / plant and 1000Rs / plant) revealed that the antagonistic effect of the F.oxysporum strain towards R.similis was independent of the initial numbers of the latter present in the root tissues. This study demonstrated that Fusarium oxysporum endophytes present in banana rhizome tissues have a potential to interfere with the multiplication of R.similis inside root tissues and therefore may serve as a tool in banana nematode management.