Bacterial Canker of Peach: Effect of Tree Winter Water Content on the Spread of Infection Through Frost‐related Water Soaking in Stems

Abstract

Several experiments were conducted to study the influence of water content in trees on dye diffusion or controlled Pseudomonas syringae pv. persicae infection spread induced in winter by water soaking after freezing and thawing. These were carried out in a cold cabinet in excised dormant hardy 1‐year‐old slightly dehydrated or rehydrated peach shoots, and in whole variably hydrated peach trees cultivated outdoors in 3001 containers. In shoots, dye diffusion was more substantial and infection more widespread when water content was higher. In potted peach trees, the spread of individual bacterial cankers which was induced by inoculating different shoots over two successive winters, was more restricted when tree water content was lower. In both years, a high positive correlation coefficient was observed between individual tree water content and mean canker length. This study revealed that stem water content in peach trees during winter and frosts is a fundamental factor in infection because it can drastically affect bacteria diffusion in cortical tissues during frost‐ and thaw‐related water soaking. The effect of water content may have important epidemiological consequences firstly due to the influence of several environmental and agronomic factors on tree water content, and then to the prevalence of frost‐related water soaking in many perennial and herbaceous plants.

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

“…During thawing, the ice crystals formed upon the frost, which occupy the intercellular spaces, begin to melt, and the bacteria suspended in the water drops are absorbed into the intercellular spaces (Sule & Seemuller, ). Therefore, it is reasonable to conceive that this process occurs several times during winter, as observed for stone fruit crops (Vigoroux, ), and Psa could effectively colonize the relevant portions of 1‐year‐old kiwifruit twigs and subsequently migrate to the leader and main trunk during the following season, eventually producing exudates after a frost event. A similar phenomenon has been previously observed for Agrobacterium tumefaciens systemically invading grapevines, chrysanthemums and marguerite daisies, for which frost injury can induce a linear or confluent array of small tumours along the vascular system of infected plants (Kado, ).…”

“…Bacterial suspensions of 1–2 × 10 9 CFU mL −1 were prepared as described above for Psa CRA‐FRU 8.43 and Pss CRA‐FRU 10.31. As soon as the twig tissues appeared water‐soaked as a result of thawing, the twigs were punctured with a sterile syringe and 5‐μL drops of the bacterial suspension were placed onto the wound, in accordance with Vigoroux (, ) and Cao et al . ().…”

Epidemiology of Pseudomonas syringae Pathovars Associated with Decline of Plum Trees in the Southwest of Germany

“…Frequent cycles of freezing and thawing favour non‐injurious, passive ingress of P. syringae or entry through frost injuries as well as spread in the intercellular space by water redistribution (Fig. 1; Zeller and Schmidle, 1979; Süle and Seemüller, 1987; Sobiczewski and Jones, 1992; Cao et al., 1999; Vigouroux, 1999). As the southern side of the trunk is exposed to direct sun light during winter, tension cracks of the bark and freeze‐thaw‐cycles are frequently expected on this side of the tree during periods of frosty weather.…”