Potato tuber moth (PTM) is a key potato crop pest in subtropical and Mediterranean areas. Tuber resistance has been found in wild species, particularly in Solanum pinnatisectum. Somatic hybrids between the latter and S. tuberosum show intermediate resistance levels. Tubers develop a strong anthocyanin reaction after larval feeding, with an early larval mortality. Furthermore, a decrease of resistance observed in tubers exposed to stressing conditions suggested the presence of an induced-defence mechanism. First attempts to analyse defence mechanisms against PTM in tubers by stimulating or attenuating resistance through physical and chemical factors are described in this work. Three experiments were performed on two tetraploid hybrid clones differing in the level of resistance (the moderately resistant clone 62 and the resistant clone 6), and the cultivar 'Désirée', used as control: 1) insect bioassay after tuber storage at 4° or 38°C. 2) insect bioassay after tuber treatment with signal defence molecules (methyl jasmonate or sodium salicylate). 3) analysis of anthocyanin reaction after wounding or after larval regurgitant coupled with wounding. Storage at 4° and 38°C significantly reduced larval mortality in somatic hybrids. These results rule out the role of thermally stable metabolites in resistance, such as glycoalkaloids or calystegines, and suggest a dynamic interaction between plant and insect. A significant slight reduction of pupal weight was observed on all genotypes treated with sodium salicylate, while less well-formed galleries were recorded on the clone 62 after methyl jasmonate (MeJa) treatment. Since the MeJa gave rise to the same resistance levels existing in the resistant clone 6, we hypothesize that different defence signal transduction patterns in cell membranes determine variations in resistance. Larval regurgitant increased anthocyanin reaction. This suggests that specific insect elicitors are able to enhance related metabolic pathways as observed in other plant-lepidoptera interactions.
|Publication status||Published - 2005|
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