Effect of heat-shock pre-treatment on tomato plants infected by powdery mildew fungus

The effect of plant heat-shock (HS) pre-treatment (40.5°C, 2 h) on Pseudoidium neolycopersici development in the susceptible and moderately resistant Solanum spp. genotypes was studied together with biochemical responses (endogenous concentrations of salicylic (SA), jasmonic (JA), abscisic acid (ABA), and peroxidase (POX) activity). In HS pre-treated S. lycopersicum, an acceleration of pathogen, chlorosis and necrosis development, strong SA, JA accumulation, and increased POX activity were detected. In S. chmielewskii, HS pre-treatment caused a slight suppression of pathogen development, increase in JA, ABA concentrations, and POX activity. HS accelerated and strengthened the development of symptoms and biochemical responses to the infection in the susceptible genotype in contrast to moderately resistant genotype with a robust defence response to an infection per se.