In Vitro Evaluation of Some Fungicides Alternatives Against Fusarium Oxysporum the Causal of Wilt Disease of Pepper ( Capsicum a nnum L.)

Abstract

The inhibitory effect of the antagonistic bioagents, chemical plant resistance inducers and some essential oils against the linear growth of two isolates of F. oxysporum the wilt pathogen of pepper (Capsicum annum L.) was evaluated in vitro. The antagonistic microorganisms, Trichoderma harzianum, T. viride, T. aureiviride, Bacillus subtilis and Pseudo- monas fluorescens were tested. Also, the tested chemical inducers were Sodium benzoate, Potassium bicarbonate, Potassium sorbate and Chitosan. Meanwhile, the tested essential oils were Cinnamon, Clove, Thyme, Lemon grass, Lemon, Mint, Pepper mint and Mustard. The obtained results indicate that the antagonistic bioagents, T. viride, B. subtilis, P. fluorescens showed superior inhibitory effect against the growth of pathogenic fungi compared with T. harzianum and T. aureiviride. The fungal mycelial growth reduced gradually by increasing of tested concentrations to reach complete reduction (100%) at the concentrations of 4% for Potassium bicarbonate and Sodium benzoate and at 6% for Potassium sorbate. Data also revealed that the fungicide Topsin-M had superior inhibitor effect on the fungal linear growth than that of tested salts. It cause com- plete growth reduction at concentration of 300ppm. Chitosan was found to affect the linear growth of the two isolates of F. oxysporum that the complete reduction in fungal growth (100%) was observed at concentration of 4.5 g/L. Results also showed that Thyme, Lemon grass, Peppermint, Clove and Mint oils had higher inhibitor effect on fungal mycelial growth than Limon, Cinnamon and Mustard oils. Fungal mycelial growth decreased significantly as the concentrations of essential oils were increased, to reach the fungal growth's minimum at the highest concentration used. Complete reduction (100%) in mycelial growth of two fungal isolates was recorded at concentration of 6% of all tested essential oils. The obtained results in the present study showed the possibility of usage antagonistic bioagents, various plant inducers and essential oils to control plant pathogenic fungi.