Towards an alternative and well-founded control of Pseudomonas infections in cherry and pear (CTRL-PSEUDO)

In Flemish pear and cherry production, bacterial canker caused by the Pseudomonas syringae  pathovars syringae (Pss) and morsprunorum (Psm), results in large losses almost every year as it is extremely difficult to control. In bacterial canker, all above-ground parts of the plant can be affected (stem, branch, leaf, bud, flower, fruit): leaves wilt suddenly, branches and well-defined pieces of bark die and sunken spots appear, buds on infected branches do not sprout or hardly sprout, etc. The aim of this project is to search for a curative control method, which does not yet exist. The researchers are therefore mapping all the factors involved in the infection. What is the diversity and virulence of the local Pss and Psm populations? What are the exact conditions (inoculum pressure, phenological stage, weather conditions) that give rise to infection in our orchards? And finally, this gathered knowledge is used to develop a reliable greenhouse pathogenicity test on  potted trees for evaluating new Pseudomonas control methods. 

The genetic characterization of the Flemish Pss and Psm populations forms the basis of this project, together with the mapping of the conditions that lead to infection. Using a newly installed sensor system in the orchards, 8 pear and 8 cherry orchards are monitored for climatic conditions along with Pseudomonas pressure, infections and phenology. Specifically, in the first season we characterize local Pseudomonas populations through isolations and identification. From the second season, their dynamics are monitored with a specifically developed multiplex quantitative PCR. The knowledge gained will make it possible to develop reliable greenhouse infection tests, for evaluating new Pseudomonas control methods.

The annual economic loss for Flemish growers due to Pseudomonas infections in pear is estimated at approximately € 42.75 M and in cherry at approximately € 0.9 M. The project anticipates that an early warning system combined with an effective control method should be able to reduce these annual losses by half within a 3-year period after the project ends. This will also contribute to maintaining the current number of pear and cherry growers in Flanders.