Molecular characterization of Erwinia amylovora strains from different host plants through RFLP analysis and sequencing of hrpN and dspA/E genes

Abstract

A total of 73 Erwinia amylovora strains obtained from 13 Maloideae host species and from Rubus spp., and isolated from different geographic areas, were assessed using RFLP and DNA sequencing analysis of the 3 ′ hrp N gene and /or of a fragment of 1341 bp of the dsp A/E region. An Erwinia pyrifoliae strain, used as outgroup, was checked in the same way. For the three strains isolated from Rubus spp. and for one strain from Amelanchier sp., RFLP analysis of the hrp N gene using the Rsa I enzyme yielded a PCR product 60 bp smaller than that of all the other strains. Sequence analysis of the gene revealed this was due to the absence of a 60 bp fragment in the noncoding region downstream of the gene. The strain PD 2915, isolated from Amelanchier sp. grown in Canada, showed five same-sense substitutions and one missense substitution at position 868 of the hrp N gene, converting aspartic acid into asparagine. Also, restriction analysis of a fragment of 613 bp of the dsp A/E region with Cfo I revealed an RFLP pattern suitable for differentiating the E. amylovora strains isolated from Rubus spp. and Amelanchier sp. from all the others. In the dsp A/E coding region, the four strains showed 13 -14 missense point mutations, in some cases yielding drastic amino acid substitutions. In addition, partial sequencing of the dsp A/E region of PD 2915 from Amelanchier sp. indicated a higher similarity to E. amylovora strains isolated from Rubus spp. than towards strains from other Maloideae hosts. The E. pyrifoliae strain showed 23 single nucleotide substitutions along the hrp N gene and 88% of nucleotide identity with E. amylovora strains in the portion of dsp A/E region. Artificial inoculations on immature pear fruits and young shoots of Maloideae and Ruboideae showed a restricted pathogenicity for the strains from Rubus and Amelanchier , with the latter inciting blight symptoms only on Amelanchier .

Characterization of Erwinia amylovora strains from different host plants using repetitive-sequences PCR analysis, and restriction fragment length polymorphism and short-sequence DNA repeats of plasmid pEA29

“…The sequence homology with other E. amylovora strains from P. communis was 99%. The difference of this strain was also pointed out by pathogenicity tests and by assessing and comparing genes involved in the pathogenicity of E. amylovora such as hrpN and dspA/E (Giorgi and Scortichini 2005). By using AFLP, Rico et al.…”

Lipopolysaccharide biosynthesis genes discriminate between Rubus‐ and Spiraeoideae‐infective genotypes of Erwinia amylovora

“…A number of studies have demonstrated very limited cross‐infectivity between Spiraeoideae‐ and Rubus ‐infecting isolates of E. amylovora : Rubus isolates are mostly unable to cause fire blight symptoms when inoculated into apple trees or immature pear fruits, whereas Spiraeoideae‐infecting isolates generally elicit a limited local response in raspberry when administered at high doses (Braun and Hildebrand, 2005; Evans, 1996; Giorgi and Scortichini, 2005). Nonetheless, cross‐infected isolates survive on and can be recovered from the nonhost plant, whilst maintaining their ability to infect their original host (Braun and Hildebrand, 2005; Evans, 1996; Giorgi and Scortichini, 2005).…”

Phenotypic and genetic diversity of Erwinia amylovora: the causal agent of fire blight

“…The sequences of the gene were almost identical in European strains (Jock and Geider 2004). A study by Giorgi and Scortichini (2005) on E. amylovora isolates originating from different continents confirmed that there was a greater variation in the gene hrpN of bacteria isolated in North America where fire blight was discovered and described for the first time in the world. RFLP analysis of genes hrpN and dspA/E revealed significant differences between the strains isolated from plants of Rubus and Amelanchier, and those from the plants belonging to the family Maloidae (Giorgi and Scortichini 2005).…”

“…A study by Giorgi and Scortichini (2005) on E. amylovora isolates originating from different continents confirmed that there was a greater variation in the gene hrpN of bacteria isolated in North America where fire blight was discovered and described for the first time in the world. RFLP analysis of genes hrpN and dspA/E revealed significant differences between the strains isolated from plants of Rubus and Amelanchier, and those from the plants belonging to the family Maloidae (Giorgi and Scortichini 2005). Restriction fragment analysis of amsB gene (involved in the production of specific polysaccharide of E. amylovora-amylovoran) showed no differences between strains isolated in Poland (Puławska et al 2006).…”