IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Annual grass fungal endosymbionts decrease the vulnerability of symbiotic-free neighbors to Sypha maydis
Autor/es:
OMACINI M; MALLARINI, M; CASAS,C; GHERSA, CM
Lugar:
Pittsburgh, Pensilvania
Reunión:
Congreso; 95th ESA Annual Meeting; 2010
Institución organizadora:
Sociedad Americana de Ecologia
Resumen:
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Background/Questions/Methods
Symbiotic
associations between plants and fungus are of major importance as drivers of
ecological processes at different organization levels and scales. Asexual
fungal endophytes of Neotyphodium (Clavicipitaceae) grow in aboveground
tissues of many cool-season grasses. These endosymbionts may alter host plant
chemistry and ecophysiology, usually increasing host´s resistance to
herbivores. Despite of the increasing awareness that grass‑endophyte symbiosis
may affect whole neighborhoods, little is known about its impact on biotic
interactions between nearby symbiotic-free plants and other organisms.
We
performed an outdoor experiment to investigate if symbiotic-free Bromus unioloides
plants gain protection from aphid herbivory owing to their proximity to Lolium
multiflorum plants defended by endophytes. We created vegetation patches (50cm
x 50cm) with four different endophyte infection levels (I:5%, II: 32%, III:
60%, IV: 95%) by sowing different proportions of Lolium multiflorum
seeds with and without the symbiont. Six months after planting date, three pots
with Bromus unioloides (focal plants) were located into each of grass
patches and were infested, one week later, with 40 aphids of Sypha maydis (Aphididae).
We measured the abundance of S. maydis live and parasitized and of
other naturally colonizing aphids in both grasses.
Results/conclusions
Endophyte
infection level of the neighboring vegetation significantly affected the
establishment of S. maydis on B. unioloides plants (P<0.0001).
Aphid abundance was four times higher in focal plants immersed within patches
of low endophyte infection (average values were 167 and 206 aphids/plant for I
and II infection levels, respectively) than within patches of high infection
(43 and 46 aphids/plant for III and IV infection levels, respectively). The
abundance of S. maydis colonizing L. multiflorum plants was low (less
than 9 aphids/plant) regardless of the treatments (P=0.80). Neither
parasitized aphids nor other aphid species were detected during the experiment.
L. multiflorum reproductive (P=0.023) and aerial vegetative (P=0.014)
biomass at the end growing season were positively related with endophyte
infection levels. B. unioloides biomass did not differ among treatments
(P=0.72). Mechanisms for this associational protection are still
unclear. However since treatments did not affect top-down controls nor B.
unioloides plant performance, we speculate that volatiles may be involved
modulating grass vulnerability to generalist aphid herbivores in endophyte
infected L. multiflorum patches.