Disease severity on the internodes was assessed 30 days post-inoculation by estimating the percentage of the area covered by lesions on the four internodes below the internode tagged at inoculation, using a modified Horsfall–Barratt scale (Barratt and Horsfall 1945) with 12 levels (1: 0–5%; 2: 5–10%; 3: 10–20%; 4: 20–30%; 5: 30–40%; 6: 40–50%; 7: 50–60%; 8: 60–70%; 9: 70–80%; 10: 80–90%; 11: 90–100%; 12: 100%). Differences between genotypes were determined by ANOVA, as described in “Statistics”.