Frost promotes the pathogenicity of Pseudomonas syringae pv. actinidiae in Actinidia chinensis and A. deliciosa plants

Abstract

Frost occurs in all major areas of cultivation, presenting a threat for the production of kiwifruit crops worldwide. A series of experiments were performed on 1-year-old, potted plants or excised twigs of Actinidia chinensis and A. deliciosa to verify whether strict relationships exist between bacterial canker outbreaks from Pseudomonas syringae pv. actinidiae (Psa) attacks and the occurrence of autumn and winter frost events. The association between the occurrence of autumn frost and the sudden outbreak of bacterial canker in A. chinensis in central Italy has been confirmed. Both autumn and winter frosts promote Psa multiplication in the inoculated twigs of both species. The day after the frost, reddish exudates oozing from the inoculation sites were consistently observed in both species, and Psa was re-isolated in some cases. During the thawing of both A. deliciosa and A. chinensis twigs, the 2-cm upward and downward migration of Psa from the inoculation site was observed within 3 min, and the leaves were consistently colonized with the pathogen. A consistent brown discoloration, accompanied with a sour-sap odour, was observed throughout the length of the excised twigs of both Actinidia species after Psa inoculation and winter frost. Psa inoculation induced a remarkably higher necrosis in excised twigs that were not frozen compared with P. s. pv. syringae inoculation. Antifreeze protection using irrigation sprinklers did not influence the short-term period of Psa and P. s. pv. syringae multiplication in both A. deliciosa and A. chinensis twigs. Thus, the damage from frost, freeze thawing and the accumulation of Psa in Actinidia twigs promotes the migration of the pathogen within and between the orchards. Taken together, the results obtained in this study confirmed that A. deliciosa is more frost tolerant than A. chinensis, autumn frosts are more dangerous to these crops than winter frosts, and in the absence of Psa, young kiwifruit plants remain sensitive to frost.

D-PSA-K: A Model for Estimating the Accumulated Potential Damage on Kiwifruit Canes Caused by Bacterial Canker during the Growing and Overwintering Seasons

“…We did not observe such a relationship for Hort16A. These differences might be caused by differences in resistance to low temperatures and pathogen differences between Hayward and Hort16A (Balestra et al, 2009; Ferrante and Scortichini, 2014; Koh et al, 2010). Differences in the resistance of kiwifruit cultivars to the bacterial canker in Korea are not clearly understood.…”

“…Temperatures above about 35°C could suppress multiplication and dispersal of the pathogen. Freezing plant tissue during the cold winter could be a major factor contributing to the development of severe bacterial canker symptoms in early spring, although the pathogenic bacterium does not display ice nucleation activity (Ferrante and Scortichini, 2014; Ko et al, 2000a, 2000b; Serizawa et al, 1989). …”

Omics, epidemiology and integrated approach for the coexistence with bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidiae

“…In parallel, epidemiological studies allowed to ascertain that autumn (i.e., 2007) and spring (i.e., 2008) frosts together with an increase of 30-35% in the rainfall precipitation during 2008, largely contributed to promote the disease and spread the inoculum in central Italy (Ferrante and Scortichini, 2013), and that the pathogen can colonise all the main organ of the plant almost all-year-round . In addition, similar to other fruit tree species, it has been demonstrated that during thawing, Psa, in case of colonisation through wounds, can systemically migrates throughout the twig vascular system within few minutes after penetration.…”

New insights on the bacterial canker of kiwifruit (Pseudomonas syringae pv. actinidiae)

“…A recent study (2014) [15] showed that frost and freeze/thawing promote the migration of the pathogen within Actinidia twigs and between the orchards. Autumn frosts are more dangerous than winter frosts, because they also promote the oozing of exudates from the wounds, which, in some cases, are a secondary source of inoculum.…”

“…Currently, the bacterial canker has spread to a pandemic scale [14] and it is the major cause of severe economic losses in all countries, such as Italy and New Zealand, where kiwifruit is a strategic crop [15].…”