Commercial Biocontrol Agents Reveal Contrasting Comportments Against Two Mycotoxigenic Fungi in Cereals: Fusarium Graminearum and Fusarium Verticillioides

Abstract

The aim of this study was to investigate the impact of commercialized biological control agents (BCAs) against two major mycotoxigenic fungi in cereals, Fusarium graminearum and Fusarium verticillioides, which are trichothecene and fumonisin producers, respectively. With these objectives in mind, three commercial BCAs were selected with contrasting uses and microorganism types (T. asperellum, S. griseoviridis, P. oligandrum) and a culture medium was identified to develop an optimized dual culture bioassay method. Their comportment was examined in dual culture bioassay in vitro with both fusaria to determine growth and mycotoxin production kinetics. Antagonist activity and variable levels or patterns of mycotoxinogenesis inhibition were observed depending on the microorganism type of BCA or on the culture conditions (e.g., different nutritional sources), suggesting that contrasting biocontrol mechanisms are involved. S. griseoviridis leads to a growth inhibition zone where the pathogen mycelium structure is altered, suggesting the diffusion of antimicrobial compounds. In contrast, T. asperellum and P. oligandrum are able to grow faster than the pathogen. T. asperellum showed the capacity to degrade pathogenic mycelia, involving chitinolytic activities. In dual culture bioassay with F. graminearum, this BCA reduced the growth and mycotoxin concentration by 48% and 72%, respectively, and by 78% and 72% in dual culture bioassay against F. verticillioides. P. oligandrum progressed over the pathogen colony, suggesting a close type of interaction such as mycoparasitism, as confirmed by microscopic observation. In dual culture bioassay with F. graminearum, P. oligandrum reduced the growth and mycotoxin concentration by 79% and 93%, respectively. In the dual culture bioassay with F. verticillioides, P. oligandrum reduced the growth and mycotoxin concentration by 49% and 56%, respectively. In vitro dual culture bioassay with different culture media as well as the nutritional phenotyping of different microorganisms made it possible to explore the path of nutritional competition in order to explain part of the observed inhibition by BCAs.

Investigating Useful Properties of Four Streptomyces Strains Active against Fusarium graminearum Growth and Deoxynivalenol Production on Wheat Grains by qPCR

“…Currently, only two commercial products based on live Streptomyces spp. are available on the European market (Mycostop ® and Actinovate ® ) and neither of them were specifically registered for FHB management [24], despite showing certain activity against F. graminearum [25]. However, diverse Streptomyces strains are likely to become part of the tools available for integrated disease control in the near future as shown by some recent patent depositions [26].…”

Potential of Trichoderma spp. and Pinus sylvestris Bark Extracts as Biocontrol Agents against Fungal Pathogens Residing in the Botryosphaeriales

“…The confrontation test of N. parvum with Trichoderma isolates resulted in a deadlock at a distance with enhanced production of dark pigmentation in N. parvum. This is expected as pigments indicate the meeting of the two genetically different mycelia while an inhibition zone indicates the diffusion of antifungal metabolites [30,31].…”

“…The interaction established between the two Trichoderma isolates, B. dothidea and D. sarmentorum induced morphological changes characterized as overgrow with replacement which indicates mycoparasitism as the mode of the action [29,30]. The confrontation test of N. parvum with Trichoderma isolates resulted in a deadlock at a distance with enhanced production of dark pigmentation in N. parvum.…”

Mycotoxins Biocontrol Methods for Healthier Crops and Stored Products

“…F. verticillioides growth and mycotoxin concentration was too reduced (49% and 56%). The application of S. griseoviridis resulted in a growth inhibition zone where the pathogen mycelium structure appeared to be altered, suggesting the diffusion of antimicrobial compounds [ 181 ].…”