The roles of Epichloë endophytes on the construction of plant defenses against diseases

GUNDEL, P.E.; ZABALGOGEAZCOA, I.; OMACINI. M.; PEREZ, L.I.

Salamanca

Simposio; 10th International Symposium on Fungal Endophytes of Grasses.; 2018

IRNASA-CSIC,Fundación General de la Universidad de Salamanca

The study of the role of leaf fungal endophytes on the interaction between host grasses and pathogens is difficult as it involves the combination of two systems that are already complex in isolation [1]. It has been proposed that the endophyte could modulate the interaction of host plants with the fungal community and, in particular with fungal pathogens [2]. Results from some studies support that symbiosis with endophytes reduces the pathogen infection, although other studies found no effects [3] or even a promotion of infection [4]. Here we propose that part of this variability can be explained through properly framing the interactions and identifying the mechanisms involved. We defined two types of pathways through which the endophytes could reduce pathogen infection in host plants: Direct pathways mediated by (i) the production of fungistatic compounds, (ii) the induction of plant defenses and/or (iii) the competition for a common resource [5], and indirect (or ecological) pathways associated with endophyte-generated changes in either the abiotic or the biotic host environment, that ultimately impact on the pathogen´s ecology (changes in soil that impact on pathogen´s colonization or the emission of volatile compounds that affect vectors behavior, for example)[6]. Finally, we identify and test the impact of the experimental approaches and life-history traits of the interacting organisms. We analyzed 21 studies that comprehended a total of 132 comparisons. The meta-analysis revealed an overall negative effect of the endophyte symbiosis on the development of fungal diseases in 17 grass species with different life-spans and geographic origin (effect size:-0.8915, CI95%: -1.0569, -0.7186). The experiments were mostly conducted in laboratory conditions, while few of them were made in the greenhouse and in the field. Both laboratory and greenhouse comparisons showed negative effects of fungal endophytes on pathogen growth and infection; however, this effect was not significant in field experiments (Qb: 215; p2