Molecular tracking of Acidovorax citrulli: Unveiling pathogen dynamics and blotch disease outbreaks through specific markers

Abstract

Acidovorax citrulli (Ac), a gram-negative bacterium, is the causal agent of bacterial fruit blotch (BFB), which poses a significant threat to cucurbit crop production worldwide. Understanding the genetic diversity of Ac is crucial for identifying sources of resistance and implementing effective disease management strategies. In this study, we conducted the first genetic characterization of Ac strains collected in Turkey using Inter-Simple Sequence Repeat (ISSR) markers. These markers were selected based on repetitive domains mapped on the complete reference genome sequence of Acidovorax citrulli strain NWB SC196. The identity of the Turkish strains was confirmed through molecular (PCR) and serological (Immunofluorescence test and ELISA) methods, while the selected ISSRs, which exhibited similarity to flanked regions in the pathogen's whole genome sequence, were employed to assess the genetic diversity among Ac strains. We compared the profiles of Turkish strains with those of a collection of Ac strains from various countries, including the US, to explore a possible common origin. Specifically, we considered the dissemination of these strains through rootstocks used for grafted seedling production (Cucurbita maxima ? Cucurbita moschata). The results demonstrated a shared genetic profile, suggesting a potential link between Ac strains collected in Turkey and foreign strains. The Mauve analysis, utilizing whole genome sequences of various Ac strains available in the NCBI database, displayed similar clustering patterns to those obtained using our selected molecular markers, confirming the discriminatory efficiency of our method. Based on the high discriminatory power of the selected markers, our proposed method offers a rapid and straightforward approach for genetic analysis of intraspecific variation and monitoring Ac gene flow across countries. The characterized strains and markers presented in this study serve as valuable resources and reference materials for further genetic investigations and tracking contamination sources associated with Ac.