Genetic Diversity of Xanthomonas arboricola pv. juglandis (synonyms: X. campestris pv. juglandis;X. juglandis pv. juglandis) Strains from Different Geographical Areas shown by Repetitive Polymerase Chain Reaction Genomic Fingerprinting

Abstract

A world‐wide collection of 61 Xanthomonas arboricola pv. juglandis strains, isolated from Persian walnut (Juglans regia L.) or obtained from international culture collections and bacterial plant diseases laboratories, were studied by means of repetitive polymerase chain reaction (PCR) genomic fingerprinting using ERIC, BOX and REP primer sets and polyacrylamide gel electrophoresis. Cluster analyses were performed by UPGMA. Copper resistance, ability to hydrolize starch and quinate metabolism of the strains was also assessed. Pathogenicity was tested by inoculating leaves and nuts of Persian walnut seedlings. Polyacrylamide gel electrophoresis allowed very clear and reproducible differentiation of the PCR products. Cluster analysis showed the existence of three major groups of strains. The first two groups were 85% genetically similar, whereas the third clustered at 78% similarity with the other two. Each group could be divided into two subgroups which clustered according to the geographical origin of the isolates. In some cases, different genomic profiles were shown by strains from one country. This is possibly due to Persian walnut cultivation being mainly based on ecotypes and/or local seedlings that have become adapted to particular environments and so have allowed selection of different X.a. pv. juglandis populations. All strains were pathogenic and positive in starch hydrolysis and quinate metabolism tests. This is the first record of copper‐resistant strains occurring outside California, USA.

Type Three Effector Gene Distribution and Sequence Analysis Provide New Insights into the Pathogenicity of Plant-Pathogenic Xanthomonas arboricola

“…The major conclusions reached in earlier population structure and phylogenetic studies concerning some X. arboricola pathovars (11,24,36,46,53,59,60,61,72,75,76) are reinforced by the results of the present study. Our phylogenetic analysis of the species X. arboricola reveals two major groups of strains, with X. arboricola pv.…”

“…Each pathovar of X. arboricola was represented by at least 10 strains, except for pathovars celebensis and poinsettiicola, for which only two strains were available in international collections, and pathovar fragariae, for which only strains studied by Janse et al (27) available in the French collection of plant pathogenic bacteria (CFBP) were included. The genetic diversity and pathogenicity of the majority of the strains of X. arboricola studied have already been assessed (11,16,24,27,36,46,53,59,60,61,72,75). The X. populi strains included representatives of the two subspecies described within this species (15).…”

“…Recently, a new bacterial disease, termed vertical oozing canker (VOC), emerged in French walnut orchards, and its causal agent was identified as a distinct genetic lineage within X. arboricola pv. juglandis (24).Because of their economic and regulatory status, X. arboricola pathovars pruni, corylina, and juglandis have already been the subject of many epidemiological and population structure studies (10,11,13,24,36,49,59,60,76). X. arboricola pv.…”

“…This is likely because Persian walnut cultivation is based mainly on local seedlings which have adapted to particular environments and thus enabled selection of different X. arboricola pv. juglandis populations (36,59). The genetic diversity of pathovar corylina is also high, because strains isolated from Corylus maxima were shown to deviate genetically and pathogenically from strains isolated from Corylus avellana (60).…”

Identification of Xanthomonas species associated with bacterial leaf spot of tomato, capsicum and chilli crops in eastern Australia

“…Xanthomonas arboricola pv. juglandis is starch-positive (Scortichini et al 2001), as were the five Australian isolates, however Xanthomonas arboricola pv. pruni is recorded as being starch-negative, indicating this trait is not uniform among X. arboricola (EPPO 2006).…”