Search

The potential to propagate Uapaca kirkiana through air layering was investigated at Igumbilo forest, Tanzania. The objective was to determine the effect of time of setting air layers and use of indole-3-butyric acid (IBA) to promote rooting. Air layers were initiated on young shoots, 1-to 2-years old, growing on mature trees. After root initiation, they were detached, potted and reared at the nursery for a further three months. Thereafter they were harvested and assessed. Two factors were investigated: effect of time at which air layers were initiated (June, September and December), and influence of IBA at 50, 100 and 150 mg l−1concentrations. Varied rooting successes were realised, being influenced by time at which air layers were initiated, IBA concentration or both. Optimal rooting of 82.5% was realised in June-initiated air layers treated with 50 mg l−1 IBA. Air layers initiated in December and treated with the control had the poorest rooting (46.7%). Application of 100 mg l−1 IBA during June significantly improved the number of roots, root length and root biomass produced. The increase in rooting ability during June is partly linked to better nutritive status, since most plants at this time have sufficient food reserves acquired during the active photosynthetic rainy period of January–May. The period is also associated with minimal plant developmental activities such as budding and flushing, which are usually antagonistic to rooting. Thus, air layering is a potential technique to propagate U. kirkiana, and can contribute effectively to capture desirable traits rapidly disappearing because of ongoing deforestation and maintain the desired fruit tree attributes once attained. Further studies are recommended to determine its cost effectiveness in relation to other vegetative techniques. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]