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Eriophyes cladophthirus perforates the wall of epidermis cells during feeding on young susceptible leaves and provokes the formation of cone-shaped feeding punctures. Callose is detected near the puncture after 20 min and the injured cells are transformed into nutritive cells. Nutritive cells are induced near the feeding sites on susceptible plants, whereas only necrotic cells appear near feeding sites on resistant plants.Mites feeding on resistant plants rapidly initiate a hypersensitive response detectable after 10 min on injured epidermal cells which then leads to severe necrosis of surrounding tissues after 1 h. No typical feeding punctures or callose deposits appear on injured cell walls. Polyphenolic compounds are detected in the necrotic region after 4 h.

Peroxidase activity and its electrophoretic pattern were studied in resistant Solanum dulcamara leaves following infestation by the gall mite Aceria cladophthirus. Total peroxidase activity increased in infested leaves and was related to enhancement of three major peroxidase isozymes. The highest activity was found for the intercellular peroxidases. The extraction procedures used suggest that these peroxidases are pathogenesis-related proteins. These results are discussed with reference to the lack of lignin barrier around the mite-induced necrotic local lesions. Key words: Aceria cladophthirus, gall mite, Solanum dulcamara, resistant plant, pathogenesis-related proteins, peroxidases isozymes.

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