EFFECT OF METABOLITES PRODUCED BY BENEFICIAL FUNGI ON THE PLANT METABOLOME, PHYSIOLOGY AND AGRONOMIC PERFORMANCE
Creators: name: Nigro, Marco
Publisher: name: Università degli Studi di Napoli Federico II
Year: 2013

description: The production of different metabolites has been proposed, in some cases, to be related to the activity of various beneficial fungi used world-wide for crop protection and fertilization. Metabolomic analysis of the interactions between plants, fungal phytopathogens and beneficial fungi has aided in the identification of several bioactive fungal metabolites that positively affect plant metabolism. Some of these compounds have direct activity against phytopathogens, but also increase disease resistance by triggering the plant defence system, and/or enhance root, stem, shoot and leaf vegetative growth, which may produce significant yield increases that are detectable in the field.
Beneficial fungi belonging to the genus Trichoderma are well known producers of bioactive metabolites, and are presently marketed as biopesticides and biofertilizers, due to their ability to protect plants by containing pathogen populations, as well as increase plant growth and development under different soil conditions. 
In this study, we have investigated the possibility of improving the effectiveness and the usefulness of fungal biocontrol agents by using selected metabolites [6-pentyl--pyrone (6PP), harzianic acid (HA) and hydrophobin 1 (HYTRA1)] able to: i) inhibit phytopathogens; ii) promote Trichoderma antagonistic activity; iii) induce resistance mechanisms in the plant; iv) stimulate growth and development of different cultures. To achieve this goal, we combined biochemical characterization of SMs and fungal strains with tests for agronomic performance of the biocontrol agents, and used agriculturally important plants (Solanum lycopersicum, Brassica rapa, Vitis vinifera) as well as Arabidopsis thaliana.
Application of metabolites isolated and characterized from Trichoderma strains improved plant growth in terms of seed germination (tomato plant), shoot length and dry weight (tomato, broccoli, grapevine and A. thaliana). Moreover, HA and 6PP stimulated systemic resistance mechanisms, including the production of glucosinolates in broccoli plant, while 6PP increased also the antioxidant activity and the polyphenol content in the grapes. The effect on the antioxidant activity and the polyphenol content was generally comparable with, or better that one obtained by using the commercial formulation based on the highly-effective strain T22 of T. harzianum. 
We have examined, by using LC-ESI-QToF MS, the metabolic changes occurring in A. thaliana treated with three Trichoderma metabolites found to be involved in the induction of disease resistance and growth promotion,. The effects of treatments on A. thaliana growth were observed. Applications of 6PP, HA and HYTRA1 increased plant root-length by 48%, 51% and 40%, respectively, as compared to the untreated control. The Trichoderma metabolite treatments were found to produce significant changes in the plant metabolome, particularly in the production of major hormones, by acting on specific pathways involved in plant defence (i.e phytoalexin production). The results obtained allow a better understanding of the role of some metabolites in the important beneficial interaction of Trichoderma fungi with various crop and model plants.