Abstract
Tomato (Lycopersicon esculentum, Mill) is a rich source of vitamins, minerals and lycopene, which has many health benefits. However, its production is hampered by bacterial wilt caused by Ralstonia solanacearum resulting in significant yield losses. Use of chemicals in the control of plant pathogens has detrimental effects on humans and the environment in terms of leaving residues in soil which later find their way into underground waters. Therefore, it is desirable to find an alternative to chemical control of this bacterial pathogen. This study investigates the potential of native Bacillus thuringiensis (Bt) for biological control of Ralstonia solanacearum (Rs) under laboratory conditions. B. thuringiensis was isolated from cultivated soil, non- cultivated soil, stagnant water, sawdust, horse dung, grain dust, dead leaves and poultry manure. R. solanacearum was isolated from stem exudates of bacterial wilt infected plants and its pathogenicity assay was carried out using 2-week-old seedlings of Beske tomato variety. The Bt and R. solanacearum isolates were then characterized phenotypically. Bt isolates were further identified using endospore and parasporal staining techniques. All the Bt isolates were tested for in-vitro antagonistic activity on R. solanacearum using agar well diffusion method. Isolates Bt2, Bt16, Bt17, Bt32 and Bt34 were confirmed as Bacillus thuringiensis while isolate Rs was confirmed as R. solanacearum. Beske showed wilting symptoms from the fourth day of inoculation and eventual death of seedlings. The zone of inhibition exhibited ranged from 0.0 mm to 20.0 mm.
 Keywords: Bacillus thuringiensis, In-vitro, Bacterial wilt, Ralstonia solanacearum, Tomato
Highlights
IntroductionThey can be processed into purées, juices and the Solanaceae family (Khokar, 2013)
Tomato (Lycopersicon esculentum Mill) belongs toThey can be processed into purées, juices and the Solanaceae family (Khokar, 2013)
17 bacterial isolates were isolated from cultivated and non-cultivated soils, stagnant waters, dead leaves and dead insects. This corroborates the findings of Argôlo-Filho and Loguercio, (2013), El-kersh et al,(2016), and Denane et al, (2017), that were able to isolate Bacillus thuringiensis (Bt) from different sources
Summary
They can be processed into purées, juices and the Solanaceae family (Khokar, 2013). Yellow tomatoes have higher vitamin A widespread throughout the world and represents content than red tomatoes, but red tomatoes contain the most economically important vegetables even lycopene, an antioxidant that may contribute to in Nigeria (Olaniyi et al, 2010; protection against carcinogenic substances (Khokar, Bergougnoux,2013).Tomatoes contribute to a 2013). They are rich in minerals, vitamins, essential amino acids, sugars and dietary. Tomato contains vitamin B and C, iron and proportions of vegetable crops get deteriorated phosphorus; its fruits are consumed fresh in salads annually during growth or post-harvest storage, or cooked in sauces, soup and meat or fish dishes.
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