Identification and population features of Xanthomonas arboricola pv. pruni, X. arboricola pv. coryli, and X. arboricola pv. juglandis strains in Iran

Identification and genetic diversity of 44 strains from three pathovars of Xanthomonas arboricola isolated from peach, plum, hazelnut, and walnut in Iran were assessed based on phenotypic features, rep-PCR (ERIC-, BOX-, and rep-PCR) analysis, and sequencing of 16S rRNA, ropD, and gyrB genes. All strains were Gram-negative and produced yellow pigment in YDC medium; were positive in catalase, levan production, lipase, H2S production from cysteine, and starch hydrolysis; and were negative in oxidase and nitrate reduction tests. rep-PCR analysis clustered the strains into three main groups at a similarity level of 50%. Strains in groups 1, 2, and 3 were isolated from stone fruit (peach and plum), hazelnut, and walnut, respectively. All strains of the first group were similar to the reference strain X. arboricola pv. pruni NCPPB 416, with a similarity index & GE; 56.5%. Strains of the second group included the reference strain X. arboricola pv. corylina NCPPB 935 and were divided into three clusters (D, E, and F) at 94% similarity level. The third group included walnut strains with X. arboricola pv. juglandis reference strain NCPPB 411 and was divided into 4 clusters (G, H, I, and J) at 64% similarity level. Nucleotide sequencing of 16S rRNA, gyrB, and rpoD genes showed that the Iranian strains isolated from peach and plum are similar to the reference strains X. arboricola pv. pruni NCPPB 416 and CFBP 3901 as well as the strains isolated in South Korea and Montenegro. The Iranian strains isolated from hazelnut had a similarity of 98.7-99.5% to the reference strains X. arboricola pv. corylina CFBP 1846 and CFBP 1847 and to the strain isolated from Italy. Finally, the Iranian strains isolated from walnut were 99.2% similar to the reference strain X. arboricola pv. juglandis NCPPB 411 as well as to the strain isolated from Korea. To the best of our knowledge, this first study of population features among three pathovars of X. arboricola strains in Iran and their genetic comparison with strains from other countries.