Fig. 1.

Effect of different N treatments on the resistance of tomato plants to Pst. Four-week-old tomato plants grown with different NO₃ ^– and NH₄ ⁺ concentrations were inoculated by dipping them in a bacterial suspension of Pst at 5×10⁵ cfu ml⁻¹. At 72 hpi, the disease rating was scored by measuring the percentage of infected leaves in relation to the total number of analysed leaves (A) and by recounting of bacterial populations by plating in agar–KB medium (B). The photograph shows a representative picture of disease symptoms in the different N treatments. Data show the average of three independent experiments of a pool of 10 plants per experiment ±SE. Letters indicate statistically significant differences (P<0.05; least-significant difference test). (This figure is available in colour at JXB online.)