Effect of extreme temperatures on powdery mildew development and Hsp70 induction in tomato and wild Solanum spp.

Changes in Hsp70 gene expression and protein level were studied in three Solanum spp. genotypes in response to short-term high and low temperatures and to infection by powdery mildew. Development of Oidium neolycopersici was compared on plant leaves and leaf discs with regard to the influence of temperature. Heat and especially cold pretreatment of host tissues inhibited pathogenesis and decreased chlorophyll concentration. Exposure to heat increased Hsp70 (70 kDa heat shock proteins) content in all three genotypes of Solanum spp., whereas the infection induced the accumulation of Hsp70 only in susceptible S. lycopersicum. These results are in accordance with the suggested role of Hsp70 chaperons in plant responses to metabolic pathway disturbances triggered by pathogen challenge.