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A Three-Way Interaction System for Understanding the Ability of Trichoderma spp. to Trigger Defenses in Tomato Challenged by Phytophthora nicotianae
Federico La Spada 1 , Mario Riolo 1, 2, 3 , Claudia Stracquadanio 1, 2 , Antonella Pane * 1 , Santa Olga Cacciola * 1
1  Department of Agriculture, Food and Environment (Di3A), University of Catania, Catania, Italy
2  Department of Agriculture, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy
3  Council for Agricultural Research and Agricultural Economy Analysis, Research Centre for Olive, Citrus and Tree Fruit - Rende CS (CREA- OFA), Rende, Italy


The understanding of the genetics of plant-defense mechanisms, which are triggered by microbial beneficial antagonists of plant pathogens during an infection process, represents a new challenge for modern Plant Pathology. This study evaluated the differential expression of plant-defense related genes during a three-way interaction plant - antagonist - pathogen in the model system tomato - Trichoderma – the oomycete Phytophthora nicotianae.
Thirty-day-old tomato seedlings were treated at the root system with a suspension of germinated conidia of two selected strains of T. asperellum and T. atroviride and then inoculated with zoospores of P. nicotianae. The defense mechanisms activated by tomato plants upon the simultaneous colonization of the root system by Trichoderma spp. and P. nicotianae were evaluated by analysing the expression of genes involved in the main plant defense pathways, namely salicylic acid (i.e.: pathogenesis-related proteins - PR1b1 and PR-P2-encoding genes), jasmonic acid (i.e.: lipoxygenases enzymes - TomLoxC and TomLoxA-encoding genes) and the tomato plant defensin protein (i.e.: SlyDF2-encoding gene) strongly involved in the tomato-Phytophthora infection process.
It was shown that during the three-way interaction, in the P. nicotianae-inoculated seedlings the PR1b1-encoding gene was up-regulated exclusively in the treatment with T. atroviride strain, while PR-P2- and SlyDF2-encoding genes were up-regulated by both T. asperellum and T. atroviride strains, supporting the hypothesis that Trichoderma can strongly elicit the expression of these plant defense mechanisms on tomato plants. Conversely, both lipoxygenase encoding-genes (i.e.: TomLoxC and TomLoxA) resulted normally expressed in all treatments.
In conclusion, this study provided a contribution to understand the attitude of Trichoderma to trigger plant-defense mechanisms during P. nicotianae infections on tomato.

Keywords: Gene Expression; plant defenses; Trichoderma asperellum; Trichoderma atroviride; biological control; Phytophthora nicotianae