Resistance of Three Bean Cultivars to Uromyces phaseoli Expressed Through Sporulation of the Fungus

Abstract Sporulation of the rust fungus Uromyees phaseoli was checked on three different Brasilian bean cultivars on the upper and lower leaf surface of primary leaves in a growth chamber at 21°C. Although the sporulating area of the pustules was greater on the upper leaf surface, the pustules on the lower leaf surface produced nearly two times more spores on all three cultivars. The total number of spores produced per pustule was 41,600/81,000 spores (upper/ lower leaf surface) for the susceptible cultivar Rosinha G‐2/C‐21 and for the cultivars which possess horizontal resistance: Carioca/C‐224 29,600/49,500 spores (upper/lower leaf surface), Roxo/C‐743 32,964/50,700 spores (upper/lower leaf surface). The two cultivars with horizontal resistance produced nearly a third less spores than the susceptible cultivar.