Evaluacion de germoplasma de frijol (Phaseolus vulgaris L.) para resistencia a mustia hilachosa

The resistance of 9 bean cv. to isolates of Thanatephorus cucumeris collected from either leaves (Th-5) or roots (Rs-8) of infected plants was tested under controlled conditions in growth chambers (22-25 degrees Celsius, 80-100 percent RH and 12 h artificial light). Adequate concn. of inoculum of virulent isolates were used. All cv. showed some degree of susceptibility. The severity on a 1-5 scale (1 = symptomless plants; 5 = more than 75 percent leaf surface infected) ranged between 4.2-5.0 for Th-5 isolate and between 2.5-4.0 for the Rs-8 isolate in all cv. The RH is the factor most affecting web blight development since infection can occur at temp. of 18 degrees Celsius at RH higher than 80 percent. (CIAT)