Comparing Acidovorax citrulli strains from melon and watermelon: Phenotypic characteristics, pathogenicity and genetic diversity

Abstract

Melon and watermelon bacterial fruit blotch, incited by Acidovorax citrulli, is limited to some areas in Brazil but causes important losses, mainly in melon-producing regions. Although genetic diversity has been observed among strains belonging to the species, they are considered a homogeneous group based on the fact that they show only slight physiological or nutritional differences. The objective of this study was to compare Brazilian strains from melon and watermelon by means of biochemical, pathogenicity, serological and molecular assays. Fifteen biochemical tests, cross inoculation between strains and hosts, ELISA and repetitive sequence analysis (rep-PCR) with the primers REP, ERIC and BOX were conducted. No differences were revealed by nutritional characterization or serology, but cross inoculation showed different pathogenicity groups, which could explain high aggressiveness of the bacteria to melon crops in some regions. Molecular analysis by BOX-PCR clustered strains according to their geographical origin, while ERIC-and REP-PCR, analyzed together, indicated genetic diversity, but without geographical or host origin relationships. One test that could be used to verify the pathogenicity of strains by inoculating detached leaf petioles, showing results in 36 h, is proposed here.

Development of Molecular Markers for Detection of Acidovorax citrulli Strains Causing Bacterial Fruit Blotch Disease in Melon

“…The development of efficient diagnostic tools for bacterial fruit blotch-causing A. citrulli strains has been the subject of intense investigation over the past few decades. Substantial population diversity exists among strains of A. citrulli , and strains are known to show differential virulence towards various cucurbit hosts [5,23,33,45,50,61,64]. Based on this differential virulence, DNA finger-printing and biochemical properties have characterized two major groups of A. citrulli , with group II strains being predominantly isolated from watermelon hosts, while group I strains are associated with non-watermelon hosts [35].…”

“…Thus, the development of efficient, reliable, and sensitive diagnostic tools for detecting A. citrulli strains is necessary [24]. A. citrulli strains were previously detected by differential or semi-selective agar media [25,26], seedling grow-out, sweat box or dome assays [27], carbon source utilization profiles, fatty acid methyl esters and serological assays [28,29,30,31,32,33,34,35], and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and Fourier transform infrared (FTIR) spectra [36]. A self-paired colloidal gold immune chromatographic test strip (Sa-GICS) [37], Raman hyperspectral imaging [38], surface plasmon resonance (SPR) imaging [34], lateral flow immune chromatographic strip (ICS) [39], cross-priming amplification (CPA)-based isothermal DNA amplification [40], and visual loop-mediated isothermal amplification (LAMP) [41] also used for A. citrulli strains detection.…”

Polyphasic analysis of Acidovorax citrulli strains from northeastern Brazil

“…In Brazil, differences in virulence were also observed in 41 A. citrulli strains tested on melon and watermelon seedlings, plants and fruits (Oliveira et al, 2007). Moreover, 22 strains from melon and watermelon were compared by biochemical, pathogenicity, serological and molecular assays, and only cross inoculation showed different pathogenicity groups (Melo et al, 2014). Considering the scarcity of studies on the genetic diversity of Brazilian A. citrulli strains isolated from melon and watermelon, this study aimed to contribute to a better understanding of the variability of A. citrulli strains based on virulence, substrate utilization profiles and sequences analysis.…”

“…Additionally, BOX-, REPand ERIC-PCR resolved the melon-and watermelonderived strains into two different groups, and the BOX primer was more efficient in separating the strains (Burdman et al, 2005). Melo et al (2014) also used BOX-PCR and found the occurrence of only one group at the 65 % similarity level among 22 A. citrulli strains collected from cucurbitaceous plants in three different Brazilian states (Rio Grande do Norte, Rio Grande do Sul and Minas Gerais), indicating the presence of only one group in Brazil. Therefore, using the BOX1A primers as a parameter, we found that all strains formed a single cluster at the 65 % similarity level and that the two groups occurred only at the 79 % similarity level, indicating low variability among the Brazilian strains.…”

Sera ve tarla koşullarında karpuz bakteriyel fide yanıklığı ve meyve lekesi hastalığının biyolojik mücadelesi

“…Hastalıkla biyolojik mücadelede antagonist bakteri, maya ve bitki ekstraktlarının kullanımının oldukça faydalı ve çevre dostu olduğu bildirilmiştir (Fessehaie and Walcott 2005, Jiang et al 2015, Medeiros et al 2009, Melo et al 2015, Mengulluoglu and Soylu 2012, Wang et al 2009). Oliveira et al (2006) sera koşullarında çeşitli endofit Bacillus bakteri izolatlarının hastalık gelişimini engellediğini saptamışlardır.…”