Abstract
It is well known that phytoalexins are produced by plants in response to biological or synthetic elici tors such as peptides, glycopeptides, saccharides and lipids. In particular, it has been reported that arachidonic (C20:4) and eicosapentaenoic (C20:5) acids present in Phytophthora infestans extracts, are strong elicitors of sesquiterpenoid phytoalexins (rishitin and lubimin) in potato tuber slices (Bostock et al., 1981; Bostock et al., 1982). In this work we have analysed: (1) the fatty acid (FA) composition of lipid fractions from extracts of different species of Phytophthora (P. infestans, P. cactorum and P. capsici) by coupled thin layer chromatography (TLC)-gas liquid chromatography (GLC)-mass spectrometry (MS) analyses; (2) the elicitor activity of potato tuber slices (5 cm × 0.5 cm chick) following addition of both lipid fractions as such of the tested species of Phytophthora and synthetic saturated and unsaturated fatty acids in a concentration range from 50 to 400 μg; (3) enzymatic activities of potato tuber extracts on lipid fractions of Phytophthora species and synthetic free fatty acids (FFA) and (4) quantification of phytoalexins (rishitin and lubimin) as their trimethylsilyl ether derivatives (TMS) by GLC-MS coupled system.
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