The effect of Beauveria bassiana inoculation on plant growth, volatile constituents, and tick (Rhipicephalus appendiculatus) repellency of acetone extracts of Tulbaghia violacea

Abstract

Aim: The purpose of the present study was to evaluate the effects of Beauveria bassiana (Hypocreales) inoculum on plant growth, volatile constituents, and tick repellency of the extracts of Tulbaghia violacea (Amaryllidaceae). Materials and methods: Eight-week-old potted seedlings of T. violacea were each inoculated with conidia of B. bassiana (strain SM3) suspended at a concentration of 1×106 conidia mL-1. Tissue colonization by fungal conidia was assessed after 3 weeks. Plant growth, volatile constituents, and tick repellency were assessed after 12 weeks post-treatment. Results: B. bassiana conidia successfully colonized leaf and root tissues of T. violacea. The growth of fungal hyphae out of the leaf and root sections occurred in 75% and 91.6% of plants, respectively. Inoculation of the plants with B. bassiana significantly (p<0.05) influenced root length and plant height but did not have substantial effects on weights and leaf number of T. violacea. While the fungus did not have significant effects on overall number of the volatile chemical constituents, significant variations in the quantity (area ratio) were observed in at least four compounds that were detected. In the tick repellency bioassay, high concentration (20 w/v%) of acetone extract from fungus-exposed plants produced the least repellent effect on Rhipicephalus appendiculatus larvae (Ixodidae), while at lower concentrations (5 w/v% and 10 w/v%) of acetone extracts of T. violacea, tick repellent activity of the extract of the fungus treatment was significantly improved and was comparable to commercial N,N-Diethyl-m-toluamide and the other treatments..