Comportamiento de 20 genotipos de frijol (Phaseolus vulgaris L.) a infecciones de la mustia hilachosa en el Estado de Tabasco, Mexico

A field experiment was carried out to evaluate the effect of the web bligh disease (Thanatephorus cucumeris = Rhizoctonia microesclerotia) on twenty lines of Phaseolus vulgaris in Tabasco, Mexico. The index of infection was scored two weeks after the flowering stage by using a scale based on the percentage of infected foliar tissue. The plant yields were recorded at the harvest. The Jamapa-4, Arriaga TB 2-1, Medellin 24, Acatlan 3-6-1, Cosver 2, Bocas 1 and Medellin-4 lines, showed yields over 1 000 kg/ha. Six other genotypes yielded between 800 and 1000 kg/ha The rest of the lines showed poor growth and were destroyed by the disease. The scale of severity used to measure the index of infection was not useful for detecting statistical differences among the genotypes tested; therefore it was not possible to regress the yield and the percentage of infected foliar tissue. Despite this limitation, this study demostrates that several genotypes with relatively high yield are available, even under the attack of the pathogen and also using the traditional cropping system. The yield recorded in some of the lines evaluated was nearly twince as high as that shown by other cultivars grown in this region. The assumed source of resistence present in some of the lines tested remains to be determined.