Effect of ectomycorrhizal fungi in the protection of Uapaca kirkiana seedlings against root pathogens in Zimbabwe

Abstract

Investigations carried out on the use of ectomycorhhizal fungi in the management of Uapaca kirkiana root diseases caused by three pathogens (Rhizoctonia solani, Phytophthora parasitica and Pseudomonas solani) revealed that different mycorrhizal fungi vary in their ability to protect roots against these respective pathogens. Difference in the disease severity in various treatments was noted to have been due to the combined effect of the intrinsic biological differences of the pathogens resulting in them having different pathogenicity and the biological differences of mycorrhizal fungi. The study also highlighted that ability of mycorrhizal fungi to protect roots against these pathogens was dependent on the colonisation efficiency, which is influenced by factors such as spore germination and hyphal growth through the soil. Certain macro- and microelements were shown to inhibit growth of pathogenic fungi such as R. solani and P. parasitica. In vitro studies indicated both Zn and Cu to be significantly effective against R. solani. These elements suppressed growth of R. solani probably through their antifungal properties. Copper was also significantly effective against P. parasitica. Effect of Ca was, on the other hand, not significantly different from the control (state) on both R. solani and P. parasitica. Findings of this work may be used to explain differences in the ability of different ectomycorrhizal fungi to protect roots against different root pathogens, particularly if the mycorrhizal fungi species differ in their nutrient sequestration.

Keywords: ectomycorrhizae; fungi; inoculum; pathogens; Uapaca kirkiana

Southern Forests 2010, 72(1): 37–45