Priming F1-resistant Tomato Hybrid (Lindo-F1) Seedlings with Copper-I-Oxide Metalaxyl Composite Fungicide before Infection Enhanced Resistance to Fusarium Wilt

Abstract

Vascular wilt disease caused by soilborne Fusarium oxysporum f.sp. lycopersici is a serious constraint to production of tomato in Southwestern Nigeria. F1-resistant tomato hybrid, Lindo-F1 seedlings were primed with Copper-I-Oxide Metalaxyl (CM) fungicide containing 65% Copper-1-Oxide in 12% Metalaxyl as a wettable powder (WP). The CM was suspended in Reverse Osmosis (RO) water and applied at four different concentrations (25, 42.5, 62.5, 87.5 mg Kg-1) to the soil in the nursery, and the seedlings were assigned names (B-, C, D- and E-tomato plant) respectively, according to the concentration of CM treatment. The control (A-tomato plant) was primed with RO water. The aim was to elicit the plant's innate defences before pathogen challenge, in addition to the direct fungitoxicity of CM. Conidia suspension of three virulent, indigenous isolates of F. oxysporum f.sp lycopersici (Sensu lato) AWO-1, ERIO-1 and IGEDE-1 were tested against the water-primed- and CM-primed Lindo-F1 seedlings. Moreover, effects of the CM on crop performance indices, disease incidence and severity were evaluated for the genetically resistant tomato alone (water-primed) and the tomato seedlings primed with CM. The CM concentrations significantly affected the performance of the seedlings in the nursery, F (8, 75) =9.358, P=0.001, with a critical concentration (42.5 mg Kg-1 soil), that adversely affected plants’ vigour. The rates of growth and development of the plants in the field in relation to the carry-over effects of CM-priming in the nursery was significant, F (6,432) =7.302, P=0.001. The rates of flowering and fruiting in relation to the concentrations of CM treatments and the infecting strain of F. oxysporum also varied significantly, F(12,972) =5.796, P=0.001. The severity of disease was significantly different among the treated and the control plants, F (18,576) =2.143, P=0.004. The C-Tomato plants produced the highest number of healthy and matured fruits.