Determination of in vitro Biocontrol Potentials of Antagonist Bacterial Isolates Against Onion Basal and Root Rot Disease Agent Fusarium proliferatu

Abstract

Various Fusarium species cause significant yield and quality losses in onion (Allium cepa L.) plants. Onion basal and root rot, caused by Fusarium proliferatum, is an emerging postharvest disease that causes severe economic losses. Although the disease has long been recognized as a major constraint to the production of Allium spp., there is insufficient information to support disease management. In recent years, a need has arisen for environmentally friendly, innovative alternative methods to avoid the use of chemical pesticides in the control of diseases that are a problem in agriculture. In this study, the biocontrol efficiency of antagonistic bacterial isolates obtained from bulbs, roots and leaves of healthy onion plants was investigated against F. proliferatum in vitro. The antagonistic activity of the bacterial isolates in inhibiting the mycelial growth of the fungal agent was determined by the dual culture assay. The bacterial isolates were identified by morphological, biochemical and proteomic (MALDI-TOF MS) methods. A total of 18 putative bacterial isolates were obtained from the bulbs, roots and leaves of healthy onion plants on selective media. As a result of in vitro dual culture assays, only six bacterial isolates (Bacillus cereus MK2, Enterobacter xiangfangensis MK3, Bacillus thuringiensis MK8, Alcaligenes faecalis MK9, Pseudomonas putida MK16 and Citrobacter freundii MK17) significantly suppressed mycelial growth of disease agent (43.89-50.56% inhibition). Bacillus cereus MK2 was found to be the most effective bacterial isolate with a 50.56% inhibition rate of mycelial growth. Overall, the results suggest that Bacillus cereus MK2 could be used as a potential biocontrol agent for a sustainable and environmentally friendly control strategy for onion fields affected by Fusarium basal and root rot disease. It is necessary to conduct further studies on the effects of the effective bacterial isolates against the pathogen in vivo and their mechanisms of action.

Recent Advances in Understanding and Controlling Fusarium Diseases of Alliums

“…Bektas and Kusek [72] utilized isolates of local phosphate-solubilizing bacteria (PSB) to observe their effect on controlling onion basal rot and found 71.5 to 75.7% mycelial growth inhibition in vitro and 77.8% disease suppression in a pot experiment. In another study, Kara et al [73] employed 18 putative bacterial isolates from healthy onion bulbs, roots, and leaves to control root and basal plate rot of onion caused by F. proliferatum. Bacillus cereus, Enterobacter xiangfangensis, Bacillus thuringiensis, Alcaligenes faecalis, Pseudomonas putida, and Citrobacter freundii were found to be effective.…”