Characterization of Xanthomonas citri subsp. CITRI isolated from grapefruit in Iran

Abstract

Xanthomonas citri subsp. citri (Xcc) strains, obtained from cankers of grapefruit trees, were characterized by phenotypic, genotypic and pathogenicity features. In addition, some strains from Mexican lime were isolated to compare with Xcc strains from grapefruit. Specific polymerase chain reaction (PCR) analyses with three primer pairs and phylogenetic analysis based on sequencing of two housekeeping genes identified all Iranian isolates as Xcc-A*. The host range of the pathogen was assessed on four Citrus spp. Based on pathogenicity test, Iranian strains were divided into two pathogenic groups. The first group, corresponding to strains from Mexican lime, was only pathogenic to Mexican lime, whereas the second group, corresponding to strains from Mexican lime and grapefruit, was pathogenic to Mexican lime and grapefruit. However, reference strain was pathogenic to Mexican lime, grapefruit, tangerine and sweet lime. An insight into the genetic population features was attempted by random amplified polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC)-PCR analysis. The combined RAPD and ERIC-PCR fingerprints divided the strains into four clusters/fifteen haplotypes. Strains isolated from grapefruit and some strains isolated from Mexican lime were grouped in cluster П. Based on our results, we determined that the sources of contamination of grapefruit trees were probably neighboring infected Mexican lime trees. To our knowledge, this is the first report of occurrence of citrus canker of grapefruit in the Fars province of Iran.