Long-term impact of biocontrol inoculants in crop residues: Novel uses and overlooked risks

• Research unit: COST
• Project number: C98.0117

Key words (English)

Crop residues; inoculant; biocontrol; pseudomonas; trichoderma; fusarium; gene expression; chitinase; mycotoxin

Research programs (English)

COST-Action 830 - Microbial inoculants in agriculture and the environment

Short description (English)

See abstract

Partners and International Organizations (English)

B, DK, FIN, F, D, GR, H, I, NL, N, PL, P, E, S, CH, GB

Abstract (English)

Microbial inoculants are increasingly being used in agriculture for biocontrol of plant pathogens during crop growth. Among the most widely studied and effective biocontrol agents are the bacteria Pseudomonas fluorescens, and fungi Trichoderma spp. In this project we have shown that both are able to colonize crop residues and we have studied the interaction between these two biocontrol agents and between each biocontrol agent and the mycotoxigenic fungi Fusarium graminearum and F. culmorum. These Fusarium survive and sporulate in crop residues, and infect subsequent rotation crops at the flowering stage. Infected grain often contains mycotoxins in concentrations that are deleterious for human and animal health, also resulting in great economic loss. A principal mechanism of biocontrol with Trichoderma is production of hypal-lytic chitinases. The Trichoderma atroviride P1 strain and derivatives used in this project contain a fusion of the Aspergillus niger goxA reporter gene with either the ech42 or nag1 5' chitinase genes. Production of the mycotoxin deoxynivalenol (DON) by pathogenic Fusarium inhibited the nag gene of the antagonist on crop residues, which may render the biocontrol agent ineffective. This is one of the first examples of pathogen signalling adversely affecting biocontrol, and has important implications for microbial ecological interactions. P. fluorescens strain CHA0 inhibited both chitinase genes of Trichoderma. This indicates that these two biocontrol agents may not be compatible when used together in biocontrol strain mixtures, and also suggests that Trichoderma is probably not suitable as biocontrol agent against DON synthesizing Fusarium. The production of the key biocontrol metabolite, 2,4-diacetylphloroglucinol, by CHA0 was not inhibited by the production of Fusarium mycotoxin. Moreover stain CHA0 survived a long period of time in a non-culturable state. Thus, we have identified a potentially useful strain for biocontrol of mycotoxigenic Fusarium. Quantification of the growth of the Fusarium and Trichoderma in crop residues and analyses of their population structures, with particular attention to microbial interactions, is part of the follow up projects (COST 835, NCCR Plant Survival and French PNETOX).

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C98.0117