Host specificity, pathogenicity and the presence of virulence genes in Iranian strains ofPseudomonas syringaepv.syringaefrom different hosts

Abstract

Pseudomonas syringae pv. 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. The syrB gene was detected in all of the tested isolates. Almond and pear isolates did not have the syrD gene. The sypA gene was detected in the almond, peach, pear and sweet cherry isolates while the sypB gene was detected in the apricot, peach, sweet cherry and wheat isolates. Almond, apricot, pear and wheat isolates gave negative results for the detection of nit gene. The gene Ach, was detected only in the peach isolate and gene hrmA, was detected only in the wheat isolate. This study indicates that host specificity exists among different Pss strains, and genes responsible for syringomycin and syringopeptin production contribute to the virulence of Pss strains.

Comparative genomics of Pseudomonas syringae reveals convergent gene gain and loss associated with specialization onto cherry (Prunus avium)

“…If this pathogenic strategy has evolved in the P2 clade, it raises the question as to how it affects host specificity and virulence. P2 strains often infect more than one host species (Rezaei & Taghavi, ). These strains probably possess fewer ETI‐inducing avirulence factors that restrict effector‐rich strains to particular hosts, so may be more successful generalists.…”

Comparative genomics ofPseudomonas syringaereveals convergent gene gain and loss associated with specialisation onto cherry (Prunus avium)

“…If this pathogenic strategy has evolved in the P2 clade, this raises the question as to how it affects host specificity and virulence. P2 strains often infect more than one host species (Rezaei & Taghavi, 2014). These strains probably possess fewer ETI-inducing avirulence factors that restrict effector-rich strains to particular hosts, so may be more successful generalists.…”

Cherry picking by pseudomonads: After a century of research on canker, genomics provides insights into the evolution of pathogenicity towards stone fruits

“…A host specificity study on cucurbits showed remarkable variation in the virulence of phylogroup 2 strains on two different host species (Newberry et al, 2019), which was postulated to be due to differences in effector repertoires. Another study by Rezaei and Taghavi (2014)…”

“…The designation of strains as pathovar syringae (i.e., Pss) within phylogroup 2 provides no information about their host range or symptoms produced, and ignores genetic diversity. In terms of host specificity, closely related strains of Pss have been isolated from different Prunus species, such as apricot, cherry, and plum and many can cross-infect (Gilbert et al, 2008;Rezaei and Taghavi, 2014;Hulin et al, 2018b). Members of the other Prunus-infecting clades may be more host-restricted.…”