Allium fistulosum Crude Extract and Optimum Irrigation Levels as Alternative Management Option of Tomato Bacterial Wilt in Greenhouse

Abstract

Tomato production in Kenya is limited due to abiotic and biotic constraints among them water availability and bacterial wilt caused by Ralstonia solanacearum. A study with objective of determining the effects of Allium fistulosumcrude extract concentrations and irrigation levels on Ralstonia solanacearum inhibition in-vitro, and bacterial wilt disease incidence and severity on tomato grown in the greenhouse was conducted at KALRO-Kakamega, Kenya. The experiment employed a single factor treatment design with combination of different levels of Allium fistulosum crude extract and irrigation treated as distinct treatments. A CRD, with three replications were used in both the laboratory and greenhouse experiments. Treatments in the laboratory experimentwere; negative control (distilled water), positive control (Greencop at 50g/20L) and Allium fistulosum concentrations at 0%, 5%, 10%, 15% and 20% while in greenhouse experiment were combinations of different levels of Allium fistulosum; 20%, 15%, 0%, positive control with four levels of irrigation, 0.5 L, 1L, 1.5 L and 2L/pot/week. Data were collected on diameter of zone of inhibition, disease incidence and disease severity and subjected to Analysis of Variance (ANOVA) using PROC GLM of the Statistical Analysis System (SAS) programme version 9.1. Tukey’s Honestly Significant Difference (Tukey’s HSD) mean separation test was conducted at α= 0.05 level. The highest inhibition mean diameter of 11.48 mm was obtained under 20% concentration of Allium fistulosum in the in-vitro antibacterial assay while the lowest inhibition mean diameter of 5.8 mm was under negative control treatment. In the greenhouse experiment, all combinations of Allium fistulosum crude extract with irrigation levels generally reduced disease incidence and severity of tomato plant compared to positive and negative controls. The lowest disease incidence and severity was recorded with the use of 20% Allium fistulosum crude extract combined with either one litre or a half a litre of water while the highest disease incidence was recorded under positive control (Greencop) and negative control (0% extract) combined with two litres of water. In conclusion, Allium fistulosum crude extract concentration of 20% combined with one litres of water/pot/week is recommended to be used as alternative eco-friendly method in tomato production systems for the management of bacterial wilt. Future Studies should base on determining the concentration of allicin in Allium fistulosum crude extract that can be able to reduce bacterial wilt disease incidence and severity in the field.