Identification of hrp Genes, Encoding Harpin Protein, in Pseudomonas avellanae (Psallidas) Janse et al.

We have identi®ed hrp genes, encoding harpin pro- teins, of two strains of Pseudomonas avellanae origin- ating, from the Latium and Piedmont regions, respectively. These strains belong to two populations di€ering in phenotypic, molecular and pathogenic characteristics. For this purpose, hrpZ primers of Pseudomonas syringae pv. syringae strain 61 (hrpZPss) and hrpW primers of Pseudomonas syringae pv. tomato strain DC3000 (hrpWPst) were used for ampli®cation, by polymerase chain reaction, of presumptive hrpZ and hrpW genes in P. avellanae strains. The hrpW primers were able to amplify, in both P. avellanae strains, a 1.2 kb fragment corresponding in size to the hrpW gene, whereas hrpZ primers did not give ampli®cation products. To obtain information about this gene, a hrpZ fragment of about 500 nucleotides was ampli®ed, using sequence-degenerate oligonucleo- tides. The nucleotide sequences of these ampli®ed hrp genes of P. avellanae are reported and compared with the known sequences of these genes reported in the GenBank-EMBL Data Bank.