Thembani Nxumalo
South Africa
Title: Evaluation of Lecanicillium muscarium as the biocontrol agent of rust diseases using Oxalis as a proxy for commercial crops
Biography
Biography: Thembani Nxumalo
Abstract
The effect of Lecanicillium muscarium on Puccinia oxalidis was investigated. Oxalis is a common edible weed characterized by high concentrations of oxalic acid. The plants were inoculated with urediospores of P. oxalidis by dusting uninfected oxalis plants with leaves of rust-infected plants. Symptoms appeared after 4-5 days. The biocontrol agent (L. muscarium) occurred naturally on the infected leaves and was isolated at the later stage of P. oxalidis development on the abaxial surface of the infected leaves. Samples of L. muscarium were taken from an infected pustule of P. oxalidis and streaked onto potato dextrose agar plates and incubated at 28oC. PDA plates with colonies of L. muscarium were placed under UV light to stimulate sporulation and from those plates’ three different concentrations 102, 104, and 106 conidia/ml1- were prepared. The prepared concentrations were supra-inoculated on rust infected leaves. The concentration of 106 conidia/ml1- provided a better control of the pathogen since on average it colonized more than 70 percent of the pustules per plant. The concentration of 104 conidia/ml1- controlled only 26. 49 percent of pustules and there was no huge difference from 102 conidia/ml1- which gave 25 percent colonization. Spore penetrations by L. muscarium on urediospores viewed by scanning electron microscope were evident on those pustules that were supra-inoculated with the concentration of 106 conidia/ml1-. Hyperparasitism was predominant on the lower concentrations which did not manifest spore penetration. The results demonstrated that L. muscarium should be applied in relatively high concentrations in order to colonize more pustules of P. oxalidis. The potential of L. muscarium in controlling rust for commercial crops will be tested on chapter under greenhouse conditions.