Root protein profiles by 2-DGE of the susceptible (A) and tolerant (B) genotypes. Total soluble protein (ca. 220 μg) was separated by 2-DGE and the spots were visualized after silver staining. Numbers indicate the protein spots successfully identified by mass spectrometry. Benchmark Protein Ladder (Invitrogen, USA) was used to estimate the molecular mass of the proteins visualized.