Fungi and their use in the possible control of Nematodes in Botswana soils

Abstract

A study assessing fungi isolated from three climatic regions of Botswana as a possible control for root knot nematodes (Meloidogyne spp.) affecting the tomato(Lycopersicon esculentum L. var. ‘Money maker’) crops was conducted. Out of 1,250 soil fungal isolates, only 232 soil fungi from the Okavango Delta, Bobirwa district and different saltpans in Botswana could be sub cultured, and screened for antagonism against Meloidogyne sp. Seven of the isolates i.e., Trichoderma sp., Penicillium sp., Dendriphiopsis sp., Fusarium chlamydosporium, Cochliobolus sativus, Aspergillus fumigatus and an unidentified sterile fungus showed potential to immobilize nematode juveniles on agar plates within 2-4 days. C. sativus and Dendriphiopsis sp. showed maximum paralysis on agar plates and eventually death of the Meloidgyne sp. juveniles. In greenhouse studies using tomato plants the fungi alleviated the effect of nematodes by increasing plant, shoot height and root weight as compared to the reference controls. Cochliobolus sativus and Trichoderma sp. showed maximum plant protection of tomato plants under greenhouse conditions. Fungi ability to produce cellulase and chitinase were some of the mechanisms studied. The results indicated that Trichoderma sp., Penicillium sp., Dendriphiopsis sp., Fusarium chlamydosporium, Cochliobolus sativus and Aspergillus fumigatus are nematode antagonistic fungi indigenous to Botswana that can be used to control nematodes as they are better adapted in comparison to introduced fungi.