FUSARIUM WILT DISEASE OF TOMATO: SCREENING FOR RESISTANCE AND IN-VITRO EVALUATION OF BOTANICALS FOR CONTROL; THE NIGERIA CASE

Abstract

Fusarium wilt disease of tomato is caused by Fusarium oxysporum f. sp. lycopersici and is a limiting factor to tomato production in Nigeria. The objectives of this study were to screen tomato varieties commonly cultivated in Nigeria to determine their host resistance status to F. oxysporum, identify fungi species associated with tomato plants showing Fusarium wilt symptoms and the in-vitro evaluation of aqueous and methanol extracts of four botanicals for bioactivity. Symptomatic sample plants were collected from three farms in tomato producing communities of Nigeria. Isolation was done by direct plating method on acidified Potato Dextrose Agar (PDA). Fungi isolates were identified by cultural and microscopic characteristics. Extracts were prepared and evaluated for bioactivity by agar dilution method. The experiment was laid in a Completely Randomized Design replicated three times. Data were analyzed by descriptive and statistical analysis. Significantly different means were separated using Least Significant Difference at 5% level of significance. Of the nine varieties evaluated, only Tomato Shanty+N showed moderate resistance to F. oxysporum, while others were susceptible. Fungi isolated from symptomatic plants were Colletotrichum spp, Curvularia lunata, Sclerotia rolfsii, Rhizopus spp, Pestalocia macrotrica, Aspergillus spp, and Fusarium oxysporum. Extracts showed bioactivity against F. oxysporum at different concentrations. Methanol as solvent in preparing of Azadirachta indica leaf extract showed the highest inhibitory properties against F. oxysporum at low concentration. This was followed by Morinda lucida and Tagetes erecta at 37.5% and 25% concentration respectively. Tomato shanty+N and low concentration methanol extracts of Azadirachta indica leaf (12.5%) are therefore recommended.