Pseudomonas syringaeDiseases of Fruit Trees: Progress Toward Understanding and Control

Abstract

Diseases of fruit trees caused by pathovars of Pseudomonas syringae van Hall are of major concern in fruitproducing areas worldwide, are exceedingly difficult to control, and result in significant economic losses. The pathogen has the ability to kill both young and older trees. Systemic infection and death of young trees is a perennial problem in nurseries, and canker development leading to the girdling and death of scaffold limbs and entire trees is a common event that can lead to the rapid demise of older orchards. For example, bacterial canker of plum caused by P. syringae pv. syringae causes annual tree mortality rates as high as 30% in Germany (43), and bacterial canker of hazelnut has resulted in the mortality of large numbers of trees in Italy and other European countries (77). Yield losses due to lesions on fruit are typically more sporadic in occurrence and variety dependent, but significant yearly losses have been reported in some instances. Finally, the pathogen's trait of ice nucleation activity also could exacerbate the importance of frost injury as a predisposing factor for infection. Frost damage in commercial orchards is a sporadic problem that facilitates colonization and the initiation of pathogenesis for these opportunistic pathogens.P. syringae and its close relatives cause diseases of monocots, herbaceous dicots, and woody dicots, and these pathogens utilize an impressive array of virulence factors such as effectors, toxins, and phytohormones to incite disease symptoms. Aspects of the systematics, ecology, and genetics of P. syringae have been reviewed and discussed by many authors (cited literature examples: 6,27,44,47,52). Extensive recent research efforts have focused on Pseudomonas diseases of herbaceous plants, and our understanding of P. syringae-host interactions has been facilitated by genome sequencing, comparative genomics, and functional studies (cited literature examples: 21,31,96).Our understanding of and ability to manage P. syringae diseases of fruit trees is relevant to our understanding of P. syringae diseases of herbaceous hosts, and vice versa. The exciting new insights into host-pathogen interactions from the model systems can give us clues on how to pro-ceed with the less genetically pliable fruit tree systems. Studies of the fruit tree systems, and comparisons with the model systems, can provide insights into the interactions of P. syringae strains with woody hosts and address relevant questions, such as: What is the role of type III secretion in infection of woody tissues? What virulence traits enable the colonization of woody tissue by P. syringae? Are there differences in the roles of toxins in diseases of woody hosts and herbaceous hosts? How did some pathogens evolve the ability to induce galls in woody hosts? Can resistance mechanisms characterized in the model-system herbaceous hosts be exploited in fruit trees?The objectives of this article are (i) to provide an overview of several Pseudomonas diseases of fruit trees, (ii) to discuss the current and emerging unde...

Microwave-assisted Quaternization of Various Pyridine Derivatives and their Antibacterial Activity

“…A variety of symptoms are associated with woody plants infected by Pseudomonas syringae. [31] Many studies investigated synthesis and antibacterial activity of quaternary ammonium salt-type antibacterial agents. [32−34] Compound (1) with thiazole moiety showed a weak antibacterial activity against all tested bacteria.…”

Scientific Opinion on the pest categorisation ofPseudomonas syringaepv.persicae(Prunier et al.) Young et al.

“…persicae (Prunier, Luisetti and Gardan, 1970;Young, Dye and Wilkie, 1978) Taxonomic position: Kingdom: Procaryota; Domain: Bacteria; Phylum: Proteobacteria; Class: Gammaproteobacteria; Family: Pseudomonadacae; Genus: Pseudomonas; species: Pseudomonas syringae Synonyms: Pseudomonas mors-prunorum f. sp. persicae (Prunier et al, 1970) Common names: Bacterial die-back of peach (EPPO, 1997); bacterial decline of nectarine and peach (Young, 1987a); bacterial canker of peach (Kennelly et al, 2007); dépérissement bactérien du pêcher (French) (EPPO, 1997)…”

“…persicae (see Figure 1) is largely similar to that described for P. s. pv. syringae, the causative agent of bacterial canker (Young, 1987b;Kennelly et al, 2007) . In autumn bacteria invade fresh leaf scars.…”

“…In autumn bacteria invade fresh leaf scars. The bacteria overwinter in cankers, dead and symptomless buds and systemically infected branches (Vigouroux, 1970;Kennelly et al, 2007). In spring, bacteria that infected leaf scars can become active resulting in blast of buds and die-back of shoots and branches (Young, 1987a).…”

“…Possibly, the risks for infection at pruning may be dependent on the physiological condition of the plant, as has been found for P. s. pv. syringae (Kennelly et al, 2007).There are no data on seed-borne infections with P. s. pv. persicae.…”