Polyphasic analysis of Acidovorax citrulli strains from northeastern Brazil

Abstract

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.

Biofilm formation by phytopathogenic bacteria Acidovorax citrulli subsp. citrulli and Ralstonia solanacearum

“…However, for CGM6 and SCN21 isolates, which were poor producers of biofilm in both media tested, there was not a direct correlation between virulence and biofilm formation. According to Silva et al (2016), A. citrulli Aac5.3 isolate shows low virulence in melon fruits while Aac1.43 has moderate virulence and the others isolated used in this study had high virulence and was not observed a correlation between these data and the biofilm formation.…”

“…A total of 13 isolates were used in this study, six of R. solanacearum of pepper (Garcia et al, 2013) and seven of A. citrulli of melon (Silva et al, 2016). These isolates were obtained by Culture Collection of the Phytobacteriology Laboratory of the Agronomic Department of the Universidade Federal Rural de Pernambuco (UFRPE), Brazil, where they were isolated, identified and biochemically characterized.…”