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United States Department of Agriculture

Agricultural Research Service

Research Project: IDENTIFICATION, CHARACTERIZATION, AND DETECTION OF FOREIGN AND NEWLY EMERGING DOMESTIC BACTERIA Title: Multilocus sequence typing reveals two evolutionary lineages of the watermelon pathogen, Acidovorax avenae subsp. citrulli

Authors
item Feng, Jianjun - CHINA AGRI. UNIV. BEIJING
item Schuenzel, Erin
item Li, Jianqiang - CHINA AGRI. UNIV. BEIJING
item Schaad, Norman

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 2009
Publication Date: August 1, 2009
Citation: Feng, J., Schuenzel, E., Li, J., Schaad, N.W. 2009. Multilocus sequence typing reveals two evolutionary lineages of the watermelon pathogen, Acidovorax avenae subsp. citrulli. Phytopathology. 99:913-920.

Interpretive Summary: Acidovorax avenae subsp. citrulli (Aac), the causal agent of bacterial blight and fruit blotch of watermelon and other cucurbits, has caused great damage to the watermelon and melon industry. Understanding the origin of this emerging disease is important for controlling outbreaks and preventing its spread. To develop a fingerprinting database and determine the possible origin of the pathogen, a molecular-based scheme was developed. In addition to the original strains of Aac from the state of Georgia, cultures were received from the International Collection of Microorganisms from Plants in New Zealand and American Type Culture Collection, in Virginia, the study included 50 strains from China, 18 strains recently isolated stains from Georgia, 30 strains from worldwide collections, and nine strains from other A. avenae subspecies. The eight original described strains of Aac from Georgia, USA had the most diversity of sequence types compared to other regions.

Technical Abstract: Acidovorax avenae subsp. citrulli (Aac), the causal agent of bacterial blight and fruit blotch of watermelon and other cucurbits, has caused great damage to the watermelon and melon industry in China and the USA. Understanding the origin of this emerging disease is important for controlling outbreaks and preventing its spread. To develop a fingerprinting database and determine the possible origin of Aac, a multilocus sequence typing (MLST) scheme was developed using seven conserved loci. In addition to the seven originally described strains of Aac stored as lyophilized cultures in the International Collection of Microorganisms from Plants and type culture received from American Type Culture Collection, the study included 50 Chinese strains of Aac, 18 strains of Aac representing 16 haplotypes determined previously by pulse-field gel electrophoresis (PFGE), 30 strains of Aac from worldwide collections and nine strains from other A. avenae subspecies, and two strains from other Acidovorax species. An eBURST analysis and phylogenetic analysis identified two major clonal sequence complexes within Aac, clonal complex 1 and 2 (CC1 and CC2). The PFGE haplotypes were identified as 3 different sequence types and grouped with either CC1 or CC2. Presence of the two clonal complexes in China suggests at least two introductions. The eight original described strains of Aac from Georgia, USA had the most diversity of sequence types compared to other regions.

Last Modified: 10/21/2014
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