Polyphasic analysis of Acidovorax citrulli strains from northeastern Brazil

Bacterial fruit blotch (BFB) of cucurbit plants is caused by Acidovorax citrulli and represents a serious concern to melon (Cucumis melo L.) growers worldwide, including those in Brazil. Thirty-four A. citrulli strains from different melon production areas of northeastern Brazil were characterized for their virulence on melon fruits and their substrate utilization and molecular profiles. Based on the analysis of BFB severity on melon fruits, the A. citrulli strains were divided into three groups, classified as mildly, moderately or highly virulent. Although host-related groups were not observed, the watermelon and melão-pepino strains exhibited only low or moderate virulence on melon fruit. Substrate utilization profiles revealed that 94 % of the 95 tested compounds were used by A. citrulli strains as a carbon source. Overall, based on substrate utilization, low variability was observed with no relationship to host of origin. The formation of one group of A. citrulli strains based on Repetitive Sequence-based PCR (rep-PCR) analysis confirmed the low variability observed in the substrate utilization analyses. Bayesian inference based on the analysis of 23S rDNA partial sequence data resulted in one well-supported clade and clustered the strains with the A. citrulli-type species with high posterior probability support. Based on the markers used, the Brazilian A. citrulli strains belong to a single group, which corresponds to the previously described Group I for this bacterium in the United States.

Polyphasic analysis of Acidovorax citrulli strains from northeastern Brazil

Bacterial fruit blotch (BFB) of cucurbit plants is caused by Acidovorax citrulli and represents a serious concern to melon (Cucumis melo L.) growers worldwide, including those in Brazil. Thirty-four A. citrulli strains from different melon production areas of northeastern Brazil were characterized for their virulence on melon fruits and their substrate utilization and molecular profiles. Based on the analysis of BFB severity on melon fruits, the A. citrulli strains were divided into three groups, classified as mildly, moderately or highly virulent. Although host-related groups were not observed, the watermelon and melão-pepino strains exhibited only low or moderate virulence on melon fruit. Substrate utilization profiles revealed that 94 % of the 95 tested compounds were used by A. citrulli strains as a carbon source. Overall, based on substrate utilization, low variability was observed with no relationship to host of origin. The formation of one group of A. citrulli strains based on Repetitive Sequence-based PCR (rep-PCR) analysis confirmed the low variability observed in the substrate utilization analyses. Bayesian inference based on the analysis of 23S rDNA partial sequence data resulted in one well-supported clade and clustered the strains with the A. citrulli-type species with high posterior probability support. Based on the markers used, the Brazilian A. citrulli strains belong to a single group, which corresponds to the previously described Group I for this bacterium in the United States.(AU)

Identificação de potenciais plantas hospedeiras alternativas de Xanthomonas campestris pv. viticola / Identification of potential alternative hosts of Xanthomonas campestris pv. viticola

Este estudo teve como objetivo identificar possíveis hospedeiras alternativas de Xanthomonas campestris pv. viticola (Xcv), visando a fornecer subsídios para o manejo do cancro bacteriano da videira. Vinte e seis espécies vegetais foram inoculadas artificialmente com o isolado Xcv3 e mantidas em condições de casa de vegetação, sendo avaliada a evolução sintomatológica da doença, como manchas necróticas angulares e lesões nas nervuras. O Xcv3 foi reisolado a partir de cada hospedeiro alternativo com sintomas, sendo identificado por PCR (Polymerase Chain Reaction), com iniciadores específicos. As espécies inoculadas que apresentaram os sintomas típicos da doença foram Glycine sp., Senna obtusifolia, Desmodium discolor, Amaranthus deflexus, Azadirachta indica, Solanum lycopersicum e Vigna unguiculata. As espécies da família Poaceae, Bidens pilosa, Emilia fosbergii, Praxelis pauciflora, Macroptilium lathyroides e Portulaca oleracea não apresentaram sintomas durante o período da avaliação.

This study aimed to identify potential alternative hosts of Xanthomonas campestris pv. viticola (Xcv), to provide data for the management of bacterial canker of grapevine. Twenty-six plant species were artificially inoculated with the strain Xcv3 and maintained under greenhouse conditions where the development of disease symptoms, such as angular necrotic spots and rib lesions were evaluated. The Xcv3 was reisolated from each symptomatic alternative host, and identified using PCR (Polymerase Chain Reaction) with specific primers. The inoculated species that showed typical disease symptoms were Glycine sp., Senna obtusifolia, Desmodium discolor, Amaranthus deflexus, Azadirachta indica, Solanum lycopersicum and Vigna unguiculata. Species of the family Poaceae, Bidens pilosa, Emilia fosbergii, Praxelis pauciflora, Macroptilium lathyroides and Portulaca oleracea were not showed during the period of evaluation.

Identificação de potenciais plantas hospedeiras alternativas de Xanthomonas campestris pv. viticola / Identification of potential alternative hosts of Xanthomonas campestris pv. viticola

Este estudo teve como objetivo identificar possíveis hospedeiras alternativas de Xanthomonas campestris pv. viticola (Xcv), visando a fornecer subsídios para o manejo do cancro bacteriano da videira. Vinte e seis espécies vegetais foram inoculadas artificialmente com o isolado Xcv3 e mantidas em condições de casa de vegetação, sendo avaliada a evolução sintomatológica da doença, como manchas necróticas angulares e lesões nas nervuras. O Xcv3 foi reisolado a partir de cada hospedeiro alternativo com sintomas, sendo identificado por PCR (Polymerase Chain Reaction), com iniciadores específicos. As espécies inoculadas que apresentaram os sintomas típicos da doença foram Glycine sp., Senna obtusifolia, Desmodium discolor, Amaranthus deflexus, Azadirachta indica, Solanum lycopersicum e Vigna unguiculata. As espécies da família Poaceae, Bidens pilosa, Emilia fosbergii, Praxelis pauciflora, Macroptilium lathyroides e Portulaca oleracea não apresentaram sintomas durante o período da avaliação.(AU)

This study aimed to identify potential alternative hosts of Xanthomonas campestris pv. viticola (Xcv), to provide data for the management of bacterial canker of grapevine. Twenty-six plant species were artificially inoculated with the strain Xcv3 and maintained under greenhouse conditions where the development of disease symptoms, such as angular necrotic spots and rib lesions were evaluated. The Xcv3 was reisolated from each symptomatic alternative host, and identified using PCR (Polymerase Chain Reaction) with specific primers. The inoculated species that showed typical disease symptoms were Glycine sp., Senna obtusifolia, Desmodium discolor, Amaranthus deflexus, Azadirachta indica, Solanum lycopersicum and Vigna unguiculata. Species of the family Poaceae, Bidens pilosa, Emilia fosbergii, Praxelis pauciflora, Macroptilium lathyroides and Portulaca oleracea were not showed during the period of evaluation.(AU)