Designing synthetic consortia of Trichoderma strains that improve antagonistic activities against pathogens and cucumber seedling growth.

ABSTRACT

BACKGROUND: Trichoderma spp. are important agricultural biocontrol microorganisms that are often used as effective components of microbial fungicides and microbial biofertilizers. However, most of these products are prepared by a single strain in monoculture, which significantly limits the biocontrol efficiency and stability of Trichoderma products. Therefore, the establishment of a design and screening approach for consortia with multi-Trichoderma strains for co-culture is of great importance to overcome the shortage of traditional Trichoderma biocontrol products. RESULTS: First, 15 Trichoderma strains were screened in terms of mycelium growth rate, antagonistic activity to a variety of pathogens, stress tolerance to high temperature and salt stress, and cucumber seedling growth promotion level. Then, the combinations of Trichoderma asperellum GDSF1009 (CGMCC NO. 9512), Trichoderma asperelloides Z4-1 (CGMCC NO. 40245), Trichoderma harzianum 10569 (CGMCC NO. 40246), and T. asperellum 10264 (CGMCC NO. 22404) were finally screened as an optimal consortium for co-culture underlying the levels of plant growth-promoting and antagonistic activity to Fusarium oxysporum and seed germination promotion relative to the monoculture of a single strain. Consortia with multiple co-cultured strains were found to generate larger amounts of free amino acids than those from the monoculture of a single strain, and a pot assay also indicated that metabolites of co-cultures were able to promote cucumber seedling growth superior to that with monoculture of a single strain, even though the promotion was better than from simply mixed cultures from each of the four Trichoderma strains. Taken together, the co-culture consortia composed of the four compatible interactive Trichoderma strains was a potential novel multiple strain biocontrol agent based on the combination of synthetic consortia design and co-culture. In the field experiment, we found that the growth-promoting effect of the co-culture fermentation filtrate was better than that of the single culture fermentation filtrate. Compared with T-Z4-1, T-1009, T-10264 and T-10569, the plant height of cucumber was increased by 22.99%, 42.06%, 24.18% and 30.09%, respectively, and the stem diameter was increased by 16.59%, 18.83%, 13.65% and 14.70%, respectively. CONCLUSION: An approach to designing and screening Trichoderma consortia for co-culture was established. The consortia co-culture presented a better performance in antagonistic activity and cucumber growth compared with a monoculture of a single strain. Thus, it is of great significance to lay the foundation for the creation of a novel Trichoderma biofungicide or biomanure to resist cucumber Fusarium wilt and promote cucumber growth.