Bacterial fruit blotch (BFB) caused by Acidovorax citrulli is a devastating disease found in many cucurbits cultivation fields. The genetic diversity for 29 strains of A. citrulli collected from various cucurbits in South Korea was determined by DNA fingerprinting with a pathogenicity test, multi locus analysis, Rep-PCR (repetitive sequence polymerase chain reaction), and URP (universal rice primers) PCR bands. Two distinct groups (Korean Clonal Complex, KCC1 and KCC2) in the population were identified based on group specific genetic variation in the multi locus phylogeny using six conserved loci and showed a very high similarity with DNA sequences for representative foreign groups [the group I (CC1-1 type) and the group II (CC2-5 type)] widely distributed worldwide, respectively. Additionally, in the case of phaC, a new genotype was found within each Korean group. The KCC1 was more heterogeneous compared to the KCC2. The KCC1 recovered mainly from melons and watermelons (ratio of 6 : 3) and 15 of the 20 KCC2 strains recovered from watermelons were dominant in the pathogen population. Accordingly, this study found that two distinct groups of differentiated A. citrulli exist in South Korea, genetically very similar to representative foreign groups, with a new genotype in each group resulting in their genetic diversity.

1.  Burdman S, Walcott RR. 2012. Acidovorax citrulli : Generating basic and applied knowledge to tackle a global threat to the cucurbit industry. Molecular Plant Pathology 13:805-815.   

2.  Dice LR. 1945. Measures of the amount of ecologic association. Ecology 26:297-302.   

3.  Feng JJ, Schuenzel EL, Li J, Schaad NW. 2009. Multilocus sequence typing reveals two evolutionary lineages of Acidovorax avenae subsp . citrulli . Phytopathology 99:913-920.   

4. Kang HW, Park DS, Park YJ, You CH, Lee BM, Eun MY, Go SJ. 2002. Fingerprinting of diverse genomes using PCR with universal rice primers generated from repetitive sequence of Korean weedy rice. Molecules and Cells 3:281-287.   

5. Louws F, Fullbright DW, Stephens CT, Bruijn FJ. 1994. Specific genomic fingerprints of phytopatogenic Xanthomonas and Pseudomonas pathovars and strains generated with repetitive sequences and PCR. Applied and Environmental Microbiology 60:2286-2295.   

6. Melo LA, Tebaldi ND, Mehta A, Marques AS. 2014. Comparing Acidovorax citrulli strains from melon and watermelon: Phenotypic characteristics, pathogenicity and genetic diversity. Tropical Plant Pathology 9:154-162.   

7. Schaad NW, Sowell G, Goth RW, Colwell RR, Webb RE. 1978.Pseudomonas pseudoalcaligenes subsp . citrulli subsp. nov. International Journal of Systematic and Evolutionary Microbiology 28:117-125.   

8. Somodi GC, Jones JB, Hopkins DL, Stall RE, Kucharek TA, Hodge NC, Watterson JC. 1991. Occurrence of a bacterial watermelon fruit blotch in Florida. Plant Disease 75:1053-1056.   

9. Song JY, Seo MW, Lim HS, Lee YS. 2015. Genetic characteristics of Acidovorax citrulli population causing bacterial fruit blotch against cucurbits in Korea. Research in Plant Disease 21:82-88.   

10.  Song WY, Kim HM, So IY, Kang YK. 1991. Pseudomonas pseudoalcaligenes subsp. citrulli : The causal agent of bacterial fruit blotch rot on watermelon. Korean Journal of Plant Pathology 7:177-182.   

11. Schaada NW, Postnikovaa E, Sechlera A, Claflinb LE, Vidaverc AK, Jonesd JB, Agarkovac I, Ignatove A, Dicksteind E, Ramundob BA. 2008. Reclassification of subspecies of Acidovorax avenae as A. Avenae (Manns 1905) emend., A. cattleyae (Pavarino, 1911) comb. nov., A. citrulli Schaad et al.,1978) comb. nov., and proposal of A. oryzae sp. nov. Systematic and Applied Microbiology 31:434-446.   

12. Tamura K, Peterson D, Peterson N, Stecher G, Nei M, Kumar S. 2011. MEGA5: Molecular evolutionary genetics analysis using maximum likelihood, evolutionary distance, and maximum parsimony methods. Molecular Biology and Evolution 28:2731-2739.   

13. Walcott RR, Fessehaie A, Castro AC. 2004. Differences in pathogenicity between two genetically distinct groups of Acidovorax avenae subsp. citrulli on cucurbit hosts. Journal of Phytopathology 52:277-285.   

14. Wechter WP, Levi A, Ling K-S, Kousik C, Block CC. 2011. Identification of resistance to Acidovorax avenae subsp. citrulli among melon (Cucumis spp.) plant introductions. HortScience 46:207-212.   

15. Willems A, Goor M, Thielemans S, Gillis M, Kersters K, De Ley J. 1992. Transfer of several phytopathogenic Pseudomonas species to Acidovorax as Acidovorax avenae subsp. avenae subsp. nov., comb. nov., Acidovorax avenae subsp. citrulli, Acidovorax avenae subsp. cattleyae, and Acidovorax konjaci. International Journal of Systematic and Evolutionary Microbiology 42:107-119.