Biocontrol measures against onion basal rot incidence under natural field conditions
2019
El-Mougy, Nehl Samy | Abedel-Kader, Mokhtar Mohamed
Laboratory and field experiments were carried out to evaluate the efficacy of the bio-agents Trichoderma harzianum, T. viride, Bacillus subtilis and Pseudomonas fluorescens and of the fungicide Carbendazim 50WP against onion basal rot caused by Fusarium oxysporum f. sp. cepae. The tested agents were found to be effective in vitro against F. oxysporum f. sp. cepae. The maximum growth inhibition of the fungal pathogen was induced by T. viride (95.5%) and T. harzianum (92.6%) followed by P. fluorescens (88.3%) and B. subtilis (79.3%), respectively. The fungicide Carbendazim 50WP caused a growth reduction of 85.7% at the concentration of 50 ppm. Complete inhibition of pathogen growth (100%) was recorded at 100 ppm. Under field conditions throughout two successive growing seasons, onion transplants immerged in a cell or spore suspension of P. fluorescens and T. viride showed the highest disease reduction, i.e. 69.5 and 61.8%, followed by 53.8, and 53.7% induced by B. subtilis and T. harzianum, respectively. Meanwhile, 22.2% disease reduction over the untreated control was induced by carbendazim 50WP. It can be concluded that the candidate bioagents could be utilized as options alternative to chemical fungicides for the management of basal rot infection of onion, also because they have v advantage of promoting soil fertility.
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