Epichloë endophytes alter inducible indirect defences in host grasses

• Autores: Li, Tao; Blande, James D.; Gundel, Pedro Emilio; Helander, Marjo; Saikkonen, Kari
• Año de publicación: 2014
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Grass-endophyte symbiosis; Induced defences; Plant volatiles; Plant-herbivory interaction
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Epichloë endophytes are common symbionts living asymptomatically in pooid grasses and may provide chemical defences against herbivorous insects. While the mechanisms underlying these fungal defences have been well studied, it remains unknown whether endophyte presence affects the host's own defences. We addressed this issue by examining variation in the impact of Epichloë on constitutive and herbivore-induced emissions of volatile organic compounds (VOC), a well-known indirect plant defence, between two grass species, Schedonorus phoenix (ex. Festuca arundinacea; tall fescue) and Festuca pratensis (meadow fescue). We found that feeding by a generalist aphid species, Rhopalosiphum padi, induced VOC emissions by uninfected plants of both grass species but to varying extents, while mechanical wounding failed to do so in both species after one day of damage. Interestingly, regardless of damage treatment, Epichloë uncinata-infected F. pratensis emitted significantly lower quantities of VOCs than their uninfected counterparts. In contrast, Epichloë coenophiala-infected S. phoenix did not differ from their uninfected counterparts in constitutive VOC emissions but tended to increase VOC emissions under intense aphid feeding. A multivariate analysis showed that endophyte status imposed stronger differences in VOC profiles of F. pratensis than damage treatment, while the reverse was true for S. phoenix. Additionally, both endophytes inhibited R. padi population growth as measured by aphid dry biomass, with the inhibition appearing greater in E. uncinata-infected F. pratensis. Our results suggest, not only that Epichloë endophytes may play important roles in mediating host VOC responses to herbivory, but also that the magnitude and direction of such responses may vary with the identity of the Epichloë–grass symbiosis. Whether Epichloë-mediated host VOC responses will eventually translate into effects on higher trophic levels merits future investigation.
Fil: Li, Tao. University of Eastern Finland. Department of Environmental Science; Finlandia
Fil: Blande, James D.. University of Eastern Finland. Department of Environmental Science; Finlandia
Fil: Gundel, Pedro Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. MTT Agrifood Research Finland. Plant Production Research; Finlandia
Fil: Helander, Marjo. University of Turku. Department of Biology; Finlandia
Fil: Saikkonen, Kari. MTT Agrifood Research Finland. Plant Production Research; Finlandia