Host specificity, pathogenicity and the presence of virulence genes in Iranian strains of Pseudomonas syringae pv. syringae from different hosts.

Pseudomonas syringaepv.syringae(Pss) strains were isolated from almond, apricot, peach, pear, sweet cheery and wheat in Kohgiluye and Boyer-Ahmad, Kordestan, Fras and Chaharmahal and Bakhtiari provinces of Iran. The strains were examined for host specificity, the presence of virulence genes and pathogenicity on different hosts. After inoculation of isolates, in compatible reactions bacterial populations increased within six days of inoculation and final cell numbers increased several-fold over initial inoculum levels, but in incompatible reactions, bacterial populations declined within four days of inoculation. Almond, sweet cherry and wheat isolates induced progressive necrotic symptoms on almond leaves and stems. Apricot, peach and sweet cherry isolates induced necrotic lesions when inoculated on apricot leaves. On pear leaves and stems, only the pear isolate incited pathogenic reaction and isolates from other hosts did not. ThesyrBgene was detected in all of the tested isolates. Almond and pear isolates did not have thesyrDgene. ThesypAgene was detected in the almond, peach, pear and sweet cherry isolates while thesypBgene was detected in the apricot, peach, sweet cherry and wheat isolates. Almond, apricot, pear and wheat isolates gave negative results for the detection ofnitgene. The geneAch, was detected only in the peach isolate and genehrmA, was detected only in the wheat isolate. This study indicates that host specificity exists among differentPssstrains, and genes responsible for syringomycin and syringopeptin production contribute to the virulence ofPssstrains. [ABSTRACT FROM AUTHOR]