IN VITRO Analysis of Antimicrobial and Phytochemical Properties of crude extracts of selected plants against the tomato wilt diseases

Abstract

The wilt disease by fungal and bacterial pathogens is one of the most devastating diseases of tomato(Solanum lycopersicum L.) worldwide. Chemical-based control of the wilt-causing pathogens oftenleads to environmental pollution and pest resistance; hence the need for alternative sustainableapproaches. We evaluated the in vitro antimicrobial and phytochemical properties of aqueous crudeextracts of roots, leaves, flowers, and barks of Solanum incanum L., Laurnea cornuta, Tagetes minutaL., Ageratum conyzoides, Opuntia monacantha, and Euphorbia tirucalli L. from Kano-Kisumu againstErwinia chrysanthema, Ralstonia solanacearum and Fusarium oxysporum isolated from diseasedtomato tissues and rhizospheres. Sterile distilled water and the amoxicillin antibiotic were used asnegative and positive control treatments, respectively. The experiment was carried out in diameters ofzones of inhibition and levels of phytochemicals determined. Ageratum conyzoides and O. monacanthaextracts were least effective against the pathogens, with means of inhibition of only up to 8.7 and 12.3mm, respectively. Euphorbia tirucalli and L. cornuta were the most effective against the pathogens,with means of inhibition of up to 30 mm. Except for anthocyanins and anthraquinones, no significant(P<0.05) differences were observed for levels of other phytochemicals in different plant extracts. Weconcluded that plant extracts showing remarkable antimicrobial activities against the pathogens canbe used to make viable formulations to combat the devastating tomato wilt disease.