Fig. 3.

Evolution of the relative fructose content [RFC, fructose/(glucose+fructose+sucrose)] after infection and regression between RFC and disease severity at 7 days post-infection (DPI) for plants grown under different N supply regimes. Data are from experiment E6 on ‘Momor’. (A) RFC of tomato stems during the course of infection, in plants grown at 2 or 15 mm${\text{NO}}_3^{-}$ in the nutrient solution. Each bar is the mean ± standard deviation of observations on five plants. Letters above the bars indicate significant differences between sampling dates according to a Student Newman Keuls test, one test per N treatment. (B) Plot of lesion length versus RFC. Lesion length on tomato stems measured 7 DPI of a highly aggressive strain (BC1) on petiole wounds of leaves 4 and 6. Each observation is the mean of the lesion length around the two infected petioles. Each symbol corresponds to one plant. The RFC and lesion lengths were measured on the same plants at 7 DPI. The solid line corresponds to an exponential regression [y = 357 × exp(−12·1x), f = 82, P < 0·0001, 10 d.f.].