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The efficient control of halo blight, caused by Pseudomonas syringae pv. phaseolicola, is primarily based on the use of pathogen-free seed. Detection of the pathogen in seeds is currently carried out with high-sensitive methods based on the detection by PCR of genes involved in the biosynthesis of phaseolotoxin, which was believed to be produced by all strains of the pathogen with epidemiological importance. However, field epidemics of halo blight in the county of Castilla y León, Spain, are often associated to nontoxigenic isolates of P. syringae pv. phaseolicola, which cannot be detected using current molecular and serological methods. The results presented in this work show the existence of nontoxigenic isolates of P. syringae pv. phaseolicola in areas other than Castilla y León, indicating the need to establish a reliable methodology for seed certification. A simple two-step methodology is presented with the aim to identify both types of isolates that is based on a multiplex enrichment PCR of seed soakates and on pathogenicity assays., El control eficiente de la grasa de la judía causada por Pseudomonas syringae pv. phaseolicola se basa principalmente en la utilización de semilla libre del patógeno. La detección del patógeno en semilla se efectúa mediante métodos altamente sensibles basados en la detección por PCR de los genes responsables de la biosíntesis de la faseolotoxina, la cual, hasta ahora, se consideraba que era sintetizada por todas las cepas del patógeno con importancia epidemiológica. Sin embargo, en la Comunidad de Castilla y León, España, las epidemias de grasa de la judía en campo se asocian frecuentemente con cepas no toxigénicas de P. syringae pv. phaseolicola, que no pueden ser detectadas con los métodos moleculares y serológicos actuales. Los resultados presentados en este trabajo demuestran la existencia de aislados no toxigénicos de P. syringae pv. phaseolicola en zonas distintas de Castilla y León, lo que implica la necesidad de establecer una metodología fiable para la certificación de semillas de judía. Con este propósito, se presenta un sencillo protocolo en dos fases que permite la identificación de los dos tipos de aislados, y que se basa en una PCR multiplex con enriquecimiento a partir de extractos de semilla y en ensayos de patogenicidad.

Xanthomonas campestris pv. glycines (Nakano) Dye is the causal agent of bacterial pustule in soybean (Glycinemax L.) Merrill. Two tests were carried out using 175 bacteria isolated in a previous work from the soybean leafletsor phyllosphere: the first one for susceptibility to three antimicrobial agents (penicillin, streptomycin and rifampicin)applied at two different doses (20 and 100 µg ml-1), and the second one for antagonism towards X. campestris. Eighteenbacterial isolates (10.3%) were resistant to penicillin and five (2.8%) to streptomycin at 100 µg ml-1; only 2% ofthe phyllosphere bacteria were resistant to rifampicin at 20 µg ml-1. Isolate 210, identified as Bacillus subtilis, was resistantto rifampicin at 20 µg ml-1, showed the highest degree of antibiosis against the pathogen and was further testedfor antagonism against the pathogenic bacteria under greenhouse conditions. In the inoculation study, treatmentof soybean leaf surfaces with B. subtilis 210 72 h before the inoculation with the pathogenic bacteria, reduced thenumber of lesions by X. campestris. There were significant differences with other treatments (P, Xanthomonas campestris pv. glycines (Nakano) Dye es el agente causal de la pústula bacteriana de la soja (Glycine max L.) Merrill. Se determinó la susceptibilidad in vitro a tres agentes antimicrobianos (penicilina, estreptomicina y rifampicina) aplicados a dos dosis diferentes (20 y 100 micro g ml sup(-1)) y la capacidad para inhibir Xanthomonas campestris de 175 bacterias aisladas de la filosfera de soja en un trabajo anterior. Dieciocho cepas bacterianas (10.3% ) fueron resistentes a penicilina y cinco a estreptomicina (2.8% ) en la dosis de 100 micro g ml sup(-1), pero sólo un 2% fueron resistentes a rifampicina en la dosis de 20 micro g ml sup(-1). El aislado 210, identificado como Bacillus subtilis, fue resistente a rifampicina en la dosis de 20 micro g ml sup (-1) y exhibió el mayor grado de antibiosis contra el patógeno (...)

Xanthomonas campestris pv. glycines (Nakano) Dye is the causal agent of bacterial pustule in soybean (Glycinemax L.) Merrill. Two tests were carried out using 175 bacteria isolated in a previous work from the soybean leafletsor phyllosphere: the first one for susceptibility to three antimicrobial agents (penicillin, streptomycin and rifampicin)applied at two different doses (20 and 100 µg ml-1), and the second one for antagonism towards X. campestris. Eighteenbacterial isolates (10.3%) were resistant to penicillin and five (2.8%) to streptomycin at 100 µg ml-1; only 2% ofthe phyllosphere bacteria were resistant to rifampicin at 20 µg ml-1. Isolate 210, identified as Bacillus subtilis, was resistantto rifampicin at 20 µg ml-1, showed the highest degree of antibiosis against the pathogen and was further testedfor antagonism against the pathogenic bacteria under greenhouse conditions. In the inoculation study, treatmentof soybean leaf surfaces with B. subtilis 210 72 h before the inoculation with the pathogenic bacteria, reduced thenumber of lesions by X. campestris. There were significant differences with other treatments (P Xanthomonas campestris pv. glycines (Nakano) Dye es el agente causal de la pústula bacteriana de la soja (Glycine max L.) Merrill. Se determinó la susceptibilidad in vitro a tres agentes antimicrobianos (penicilina, estreptomicina y rifampicina) aplicados a dos dosis diferentes (20 y 100 micro g ml sup(-1)) y la capacidad para inhibir Xanthomonas campestris de 175 bacterias aisladas de la filosfera de soja en un trabajo anterior. Dieciocho cepas bacterianas (10.3% ) fueron resistentes a penicilina y cinco a estreptomicina (2.8% ) en la dosis de 100 micro g ml sup(-1), pero sólo un 2% fueron resistentes a rifampicina en la dosis de 20 micro g ml sup(-1). El aislado 210, identificado como Bacillus subtilis, fue resistente a rifampicina en la dosis de 20 micro g ml sup (-1) y exhibió el mayor grado de antibiosis contra el patógeno (...)