Development of common blight and accumulation of fluoride in Red Kidney bean plants exposed continuously or intermittently to hydrogen fluoride

Se inocularon por aspersion plantas de frijol cv. California Light Red Kidney de 4 semanas de edad con Xanthomonas campestris pv. phaseoli resistente a rifampina para establecer una poblacion en la superficie foliar en una hoja y una lesion en otra hoja de cada planta. En un expt., las plantas se expusieron continuamente a 0 o 1 microgramo de F/m(3) (como fluoruro de hidrogeno) o intermitentemente a 3 o 5 microgramos de F/m(3) durante 15 dias. En el otro expt., las plantas se expusieron continuamente a 0 o 1 microgramo de F/m(3) durante 15 dias, a 3 microgramos de F/m(3) durante 5 dias o a 5 microgramos de F/m(3) durante 3 dias despues de la inoculacion. Los tratamientos con fluoruro en ambos expt. dieron lugar a una dosis contaminante total de 15 microgramos de F/m(3) dias. Se midio el diametro de las lesiones y periodicamente se tomaron muestras de las hojas para determinar la acumulacion de fluoruro. Los tratamientos de exposicion intermitente no afectaron el crecimiento final de las lesiones. Sin embargo, el tamano y la expansion de las lesiones aumento linealmente con el incremento del fluoruro en el follaje. La exposicion intermitente al fluoruro no afecto el crecimiento de poblaciones epifitas de la bacteria. Ni el regimen de exposicion ni la concn. del fluoruro en el aire o en el follaje afectaron el desarrollo de las lesiones o de las poblaciones del patogeno en la superficie foliar de las plantas expuestas continuamente. (RA-CIAT) spa

Four-week-old bean plants (cultivar California Light Red Kidney) were spray inoculated with rifampin-resistant Xanthomonas campestris pv. phaseoli to establish a leaf-surface population on one leaf and a lesion on another leaf of each plant. In one experiment, plants were exposed to 0 or 1 micrograms F m(-3) (as hydrogen fluoride) continuously or 3 or 5 micrograms F m(-3) intermittently for 15 days. In the other experiment, plants were exposed continuously to 0 or 1 micrograms F m(-3) for 15 days or 3 micrograms F m(-3) for 5 days or 5 micrograms F m(-3) for 3 days after inoculation. Fluoride treatments in both experiments resulted in a total pollutant dose of 15 micrograms F m(-3) days. Diameters of lesions were measured and leaves were sampled periodically to determine fluoride accumulation. Intermittent exposure treatments had no effect on final lesion growth. However, lesion size and expansion increased linearly with increasing fluoride in foliage. Intermittent fluoride exposure had no effect on growth of epiphytic populations of the bacterium. The development of lesions and leaf- surface populations of the pathogen exposed continuously were not affected by the exposure regime or the concentration of fluoride in air or foliage. (AS) eng