Resistance to bacterial diseases

During 1984 a collaborative research effort between CIAT and the National Vegetable Research Station (Wellesbourne, England) was started to broaden the knowledge of halo blight caused by Pseudomonas phaseolicola. Isolates of the halo blight pathogen were collected from bean growing areas of Latin America and Africa. Results of preliminary pathogenicity tests show the apparent occurrence of unknown variability in pathogenicity of P. phaseolicola different from the known races 2 and 3. Additionally, 230 bean cv. were evaluated for their reaction to halo blight under field conditions in Popayan. Of these, 147 were selected as resistant and 55 as intermediate. In another series of trials, a cross of PI 319443 x G 40111 was made to study the inheritance of common bacterial blight (Xanthomonas phaseoli) resistance from the resistant Phaseolus acutifolius parent. Significant dominance and additive genetic effects were observed, and 3 genetic factors are believed to control the resistance. A 2nd major breeding project in common bacterial blight resistance was conducted to recombine intermediate levels of resistance into black-seeded cv. having commercial grain type, high yield potential, and resistance to BCMV. (CIAT)

Durante 1984 se inicio un esfuerzo de investigacion coloborativo entre CIAT y National Vegetable Research Station (Wellesbourne, Inglaterra), para ampliar el conocimiento del anublo de halo causado por Pseudomonas phaseolicola. Se recolectaron aislamientos del patogeno del anublo de halo en areas productoras de frijol de America Latina y Africa. Los resultados de las evaluaciones preliminares de patogenicidad muestran la ocurrencia aparente de variabilidad desconocida en la patogenicidad de P. phaseolicola diferente de las razas 2 y 3 conocidas. Se evaluaron, ademas, 230 cv. de frijol por su reaccion a anublo de halo en condiciones de campo en Popayan. De estos, 147 se seleccionaron como resistentes y 55 como intermedios. En otra serie de ensayos, se hizo un cruzamiento de PI 319443 x G 40111 para estudiar la herencia de la resistencia al anublo bacteriano comun (Xanthomonas phaseoli) a partir del progenitor resistente Phaseolus acutifolius. Se observaron dominancia significativa y efectos geneticos aditivos y se cree que 3 factores geneticos controlan la resistencia. Se realizo un segundo proyecto de mejoramiento por resistencia al anublo bacteriano comun para recombinar los niveles intermedios de resistencia en cv. de semilla negra que tienen tipo de grano comercial, alto potencial de rendimiento y resistencia a BCMV. (RA- CIAT)