Neotyphodium impacts on soil nematode communities: rhizosphere- and litter-mediated interactions.

OMACINI M; CHANETON,EJ; GHERSA,CM

Christchurch, Nueva Zelanda

Congreso; 6th International Symposium on Neotyphodium/Grass Interactions; 2007

There is a growing recognition that endophyte effects on host plant traits may propagate through food chains, both above- and belowground. However, several issues still need be addressed to enhance our current understanding of endophyte impacts on multitrophic species assemblages. This paper focuses on Neotyphodium effects on the structure of soil-nematode communities mediated by two consecutive generations of host plants. We predicted that the abundance and diversity of different nematode functional groups in the soil food web would be modified by the endophyte through a reduction of both herbivorous taxa (rhizosphere-mediated effects) and microbivorous and saprophagous taxa (litter-mediated effects). We performed a factorial experiment that included Lolium multiflorum plants with different levels of infection by N. occultans (-E: low and +E: high) sown in experimental microcosms covered with litter previously produced by –E and +E plants, and exposed to two different watering regimes.  At the end of the growing season, the soil beneath host plants was sampled to determine the composition and abundance of soil nematodes. Nematodes were assigned to six functional groups occupying four different trophic levels. Results will address: (i) the impact of microbial leaf symbionts on the abundance and diversity of soil invertebrate consumers with different feeding habits, (ii) the occurrence of bottom-up trophic cascades induced by endophyte infection, and (iii) the potential role of litter accumulated by previous generations of endophyte-infected plants on soil nematode communities.