Host selection in the willow sawfly Nematus oligospilus and secondary metabolites in Salix spp

BRACCINI CELINA; CERRILLO TERESA; MARTINEZ DIAZ ROMINA; CHLUDIL HUGO DANIEL; LEICACH SILVIA ROSA; FERNANDEZ PATRICIA CARINA

Congreso; 1st Latin American Meeting of Chemical Ecology; 2010

Host selection in the willow sawfly Nematus oligospilus and secondary metabolites in Salix spp   Celina L. Braccini1,3, Teresa Cerrillo2, Romina Martínez3, Hugo D. Chludil3, Silvia R. Leicach3, Patricia C. Fernandez2,3   E-mail: pcfernan@agro.uba.ar   1Instituto de Recursos Biológicos, CNIA-INTA. De los Reseros y las Cabañas S/N, Castelar Buenos Aires 2 EEA Delta del Paraná, INTA. Paraná de las Palmas y canal Comas, Campana, Buenos Aires 3 Cátedra de Biomoléculas, Facultad de Agronomía, UBA. Av. San Martin 4453, CABA, Argentina     The willow sawfly Nematus oligospilus (Hymenoptera: Tenthredinidae) is a major pest of willows. It causes severe defoliations in different species from the genus Salix [1]. Here, we evaluated host selection considering different Salix genotypes in field and lab experiments. Since the capacity of herbivores is frequently related to the presence of secondary metabolites of the host plant [2], the phenolic derivatives profile of the different genotypes is been studied in order to correlate them with host selection behavior. During field experiments, 115 individuals or genotypes of Salix spp were evaluated. The highest level of damage by defoliation was recorded on S. nigra, while the lowest was recorded on S. viminalis. In the laboratory, the following genotypes were compared in multiple choice oviposition experiments: S. babylonica var sacramenta, S. nigra 4, S. viminalis, the hybrids S. babylonica x S. alba and S. matsudana x S. alba and ED1, obtained from the controlled crossing between (S. babylonica x S. humboldtiana) x S. matsudana. Multiple choice oviposition lab experiments showed that S. nigra was highly preferred, which suggest that the highest level of damage observed in the field can be related with a high oviposition preference. On the other hand, S. viminalis showed a low oviposition preference and relatively low fecundity (ie. number of mature eggs present in the female oviduct at the time of hatching), which could explain the low level of damage detected in the field for this genotype. Differences in the chromatographic profiles of the different genotypes are currently been evaluated by HPLC analysis. These differences will be correlated with their susceptibility, especially related to its phenolic derivatives composition. This information is a first step in an attempt to reveal mechanisms of host selection in the willow sawfly aiming to find an oviposition signal that can be useful for crop protection.   [1] Cerrillo T. 2009a. Jornadas de Salicáceas 2009. Argentina. [2] Hadacek F. 2002. Critical Reviews in Plant Sciences, 21 (4): 273-322.   Financial support from UBACYT G067, Universidad de Buenos Aires and PNFOR 2212-042-121, Instituto Nacional de Tecnología Agropecuaria, Argentina