Pathogenicity of isolates of Xanthomonas campestris pv. Phaseoli

Abstract

In studies conducted at the International Center for Tropical Agriculture (Colombia), isolates of Xanthomonas campestris pv. phaseoli (Smith) Dye from the State of Goiás and Federal District (Brazil) were compared for pathogenicity with isolates from other countries. In the first inoculation test, isolates Xp CNF n. 3, 5, 6, 8, 15, 16, 17 (Brazil), Xp C-6, and Xp C-123 (Colombia) were used with P. vulgaris line 'L-32'. Inoculation method consisted of clipping the primary leaves. Symptoms recorded seven days after inoculation allowed the separation of the isolates into three groups in decreasing order of pathogenicity: 1) Xp CNF n. 3, 5, 6, 8, 15,16, Xp C-123; 2) Xp C-6; 3) Xp CNF n. 17. In the second test, isolates Xp CNF n. 3, 15, 16, 17 (Brazil), Xp C-6, Xp C-123 (Colombia), Xp S (USA), Xp U-2 (Uganda) and Xp PR-033 (Puerto Rico) were used with P. vulgaris lines 'L-32', 'P.I. 207.262', the cultivar 'Jules', and P. acutifolius line 'p. 597, Plants were inoculated and evaluated as in the first test. The isolates were separated into four groups in decreasing order of pathogenicity: 1) Xp CNF n. 3, 5, 16, Xp C-123, Xp PR-033, Xp U-2; 2) Xp C-6;3) Xp CNF n. 17; 4) Xp S. Large differences were observed in the behavior of the lines and cultivars tested. 'P.597' was highly resistant, 'Jules' showed half the symptoms of the susceptible line 'L-32', and 'P.I. 207.262' was intermediate between 'Jules' and 'L-32'.