CHARACTERIZATION AND GENETIC DIVERSITY OF PSEUDOMONAS SYRINGAE FROM STONE FRUITS AND HAZELNUT USING REPETITIVE-PCR AND MLST

Abstract

A total of 33 bacterial isolates from sweet cherry (Prunus avium L.), sour cherry (P. cerasus L.), plum (P. domestica L.), and hazelnut (Corylus avellana L.) showing disease symptoms in Poland and Italy were first identified phenotypically using conventional techniques. Sixteen isolates were classified as Pseudomonas syringae pv. syringae (Pss), 12 as P. syringae pv. morsprunorum (Psm) race 1, and five as Psm race 2. Detection of toxin production, showed that out of 16 Pss strains, 11 possessed the syrB gene, whereas three strains of Psm race 1 had the cfl gene and three strains of Psm race 2 had the gene encoding yersiniabactin (irp1). Repetitive-sequence PCR (rep-PCR) using BOX and ERIC primer sets revealed three separate clusters that were consistent with the phenotypically identified pathovars and races. The only exception were two strains of Psm race 2 that did not possess irp1. In this case, both BOX and ERIC-PCR fingerprints showed that their patterns were more similar to those obtained from Pss strains. Twenty representative strains were also used for multilocus sequence typing (MLST). In particular, MLST of gyrB, gapA, gltA and rpoD genes allowed a clear allocation of the strains into three separate clusters corresponding to Pss and Psm race 1 and 2.