An appraisal on the ethnobotany and antimicrobial activity of botanicals used for managing plant diseases in South Africa

Abstract

Increased food insecurity caused by factors such as plant pests and pathogens has prompted the use of botanicals as alternative control agents. In this review, the ethnobotany and antimicrobial effect of botanicals used for the management of plant diseases in South Africa were critically assessed. Electronic databases were accessed for relevant scientific literature that met the inclusion criteria. The systematic assessment yielded 16 studies that generated an inventory of 66 plant species (44 families) that are used in managing microbial-related plant diseases. The dominant plant families were Fabaceae and Solanaceae with each represented by five plant species. Antifungal activity was the only assay-type recorded for evaluating the plant species while the microplate dilution method (62.5%) was the most used technique. The leaves (87%) were the most common plant part that have been evaluated for antifungal activity, while acetone (69%) was the most popular solvent used for extracting the plant materials. Approximately 80% of the screened plants demonstrated promising antifungal activity against phytopathogens. For instance, the acetone extract of Breonadia salicina leaves had significant antifungal activity against Penicillium janthinellum (Minimum Inhibitory Concentration, MIC = 0.08 mg/ml), while the acetone extract of Markhamia obtusifolia leaves displayed strong antifungal activity against Aspergillus f lavus (MIC of 0.08 mg/ml) and Fusarium verticilloides (MIC of = 0.08 mg/ml). Breonadia salicina, Harpephyllum caffrum, Lantana camara, Moringa oleifera, Tagetes minuta and Vangueria infausta were identified as the most screened plants, showing promising antifungal activity against the highest number of phytopathogens (at least 3 studies reporting =2 pathogens). Among the tested phytopathogens, the genus Fusarium (69%) was the most tested fungal strain. Overall, South Africa has limited ethnobotanical studies targeting botanicals with potential to manage microbial-related plant diseases. In addition, more effort should be directed on antimicrobial activity studies relating to the other phytopathogens such as bacteria and viruses as they are cause substantial crop loses.