Fungicidal effects of Commiphora swynnertonii (Burrt.) and Synadenium glaucescens (Pax.) against tomato fusarium wilt disease

Abstract

Tomato fusarium wilt disease is an important soil-borne disease caused by Fusarium oxysporum f. sp. Lycopersici (FoL) worldwide. The disease causes yield losses of about 90% worldwide. This study aimed to evaluate the extracts of C. swynnertonii (resins) and S. glaucescens (latex, fresh and dry leaves) for their efficacy against FoL. In the laboratory, a 4 × 4 factorial experiment in a Complete Randomized Design (CRD) was carried out to evaluate resins, latex, fresh, and dry leaves each in four concentrations (0.01 g/ml, 0.05 g/ml, 0.1 g/ml and 0.15 g/ml). The negative and positive controls were Sterile Distilled Water (SDW) and a Linkmil 72 WP (Mancozeb 64% + Metalaxyl 8%) respectively. In a screenhouse, resins, latex, and fresh and dry leaves, each at 0.15 g/ml were applied on pre-inoculated tomato plants to manage TFW disease. The experiment was laid out in a Randomized Complete Block Design (RCBD) with four replications. The negative and positive controls were the untreated soil and soil treated with Linkmil 72 WP respectively. The differences between extracts in the inhibition of radial mycelial growth of the pathogen were highly significant (p = 0.000). The efficacy of the plant extracts against in vitro growth of FoL was significantly dependent on the application dose. The inhibition of mycelial growth caused by latex and dry leaves was higher than that of Linkmil 72 WP (23.58%) and SDW (0%) by 41% and 65% respectively. Findings show that there was a TFW disease reduction of 72.92% 68.75% and 56.25% in plants treated with dry leaves, the latex of S. glaucescens, and resin of C. swynnertonii in that order. Plant extracts had significant effects (p = 0.000) on plant growth. The plants treated with dried leaf powder attained the highest height, the number of branches/plant, leaves/plant, and leaf area of 85.85 cm, 19.25,99.5 and 59.39 respectively. The findings benchmark the fungicidal potential of C. swynnertonii and S. glaucescens.