Mycoparasitic nature of Bionectria sp. strain 6.21

Abstract

Abstract:In this study, a Bionectria sp. strain isolated from citrus rhizosphere was evaluated for its potential in inhibiting the growth of Rhizoctonia solani and Pythium aphanidermatum. It was demonstrated that Bionectria sp. 6.21 inhibited the growth of P. aphanidermatum and R. solani. In dual cultures, however, the antagonist only parasitised R. solani. Regarding the assay involving P. aphanidermatum, a lack of mycoparasitic ability was demonstrated. Crude extract of Bionectria completely inhibited the mycelial growth of both fungi.It appears that the main mechanism involved in the antagonism of Pythium by Bionectria is through antibiotic production. The antagonistic fungus released extracellular secondary metabolites. The metabolites were found to be inhibitory to both plant pathogenic fungi. From the crude extract, eleven fractions were obtained and tested for their antifungal properties. Two of them showed very strong activity against P. aphanidermatum. The obtained results indicated that this biocontrol agent has both antibiotic and mycoparasitic properties. On the other hand, evidence obtained from Scanning Electron Microscopy (SEM) suggests the involvement of an enzymatic process, with enzymatic digestion playing a major role in the parasitism of Bionectria sp. 6.21. In conclusion, these results provide evidence that mainly due to mycoparasitism, this strain has the potential to become a good candidate for biological control.

Fungal Endophytes as Biocontrol Agents against the Main Soil-Borne Diseases of Melon and Watermelon in Spain

“…We observed both the secretion of inhibitory substances and the presence of hyperparasitism (presence of hyphal lysis of the pathogen) in dual culture confrontations for B. ochroleuca (Figure 3d). Similar results were reported by Soares de Melo [50], in which a B. ochroleuca strain showed a hyperparasitic mechanism against pathogenic genera like Rhizoctonia or Pythium, and by Rodriguez [51], who indicated the mixed nature of control mechanisms of a Clonostachys rosea (=B. ochroleuca) strain, since it produced either antibiotic substances and hyperparasitized Sclerotinia sclerotiorum in dual culture assays.…”