CHANGES IN SUGAR CONTENT DURING INDUCTION OF SYSTEMIC ACQUIRED-RESISTANCE TO LATE BLIGHT CAUSED BY PHYTOPHTHORA-INFESTANS (MONT) DE BARY INPOTATO

Resistance of plants to their pathogens may be systemically enhanced b y a localized induction treatment, a characteristic named systemic acq uired resistance (SAR). Changes in amounts and proportions of sucrose, glucose and fructose were examined in induced and noninduced potato p lants (Solanum tuberosum L. cv. Matilda) before, and 1-9 days after ch allenge inoculation. The potato plants were induced and challenged wit h Phytophthora infestans (Mont.) de Bary. Plants which were non-induce d and non-challenged were also tested (referred to as non-treated). Th e sugars were analysed using high-performance anion exchange chromatog raphy with pulsed electrochemical detection, HPAE-PED (Dionex system). The amounts as well as the proportions of sucrose, glucose and fructo se were similar throughout the experimental period in the non-treated plants. Tn induced plants, before challenge inoculation, the amount of sucrose was 44% lower than in non-treated plants. One day after chall enge inoculation, the amount of sucrose had decreased by 79% in non-in duced plants compared with non-treated. plants, while the induced plan ts were much less affected. The total amount of all sugars were approx imately the same 1 day before and 9 days after the challenge inoculati on in all treatments. However, 1 day after challenge inoculation, a 65 % decrease in total amount was observed in the non-induced plants comp ared with the smaller reduction of 37% in the induced plants. The larg e differences in sugar amounts and proportions between the different t reatments are discussed.