Efficiency Evaluation of Local Isolates of Pseudomonas fluorescens and Bacillus cereus Against Fusarium oxysporum f. sp. lycopersici the Causal Agent of Tomato Vascular Wilt

Abstract

In an attempt to control Fusarium oxysporum f. sp. lycopersici on tomato, and to reduce tomato yield losses, by the application of local bacterial isolates, isolated from the rhizosphere of tomato plant and Trifolium purpureum as biological control agents. Four of these isolates belong to Pseudomonas fluorescens and 4 belong to Bacillus cereus. Their ability to inhibit infection was tested in vitro by two methods: the sectors method using bacterial suspensions and well-plate assay method using bacterial filtrates. The antagonistic activity was evaluated on plants in pots. The results obtained showed that the most effective bacterial isolate in inhibiting the growth of the fungal pathogen using the sectors method through culture suspensions was Bacillus cereus J02 (with a biocontrol efficacy of 20.36%). On the other hand, using the well-plate assay method, the strongest isolate was Bacillus cereus I91 (with an inhibition rate of 33.3%). The isolate Pseudomonas fluorescens A12 demonstrated the highest reduction in disease index (3.33%) compared to the infected control (70%). Moreover, it increased growth parameters (plant height, root and shoot dry weight) but did not inhibit the growth of the fungal pathogen in vitro. The isolate RIZN belonging to Bacillus cereus, isolated from the roots of Trifolium purpureum, exhibited inhibition of fungal infection both in vitro (25.3%) and on plants (disease Incidence 16.67%). These results contributed to the development of a potential biocontrol agent against tomato Fusarium wilt disease.

Keywords:

Fusarium oxysporum f. sp. lycopersici, Bacillus cereus, Pseudomonas fluorescens, Tomato, Syria