First steps toward the development of molecular markers associated with Sharka resistance in European plum (Prunus domestica L.) – a project presentation

Sharka disease is caused by the plum pox virus (PPV) and is one of the most important diseases in stone fruit production. This disease was first described in Eastern Europe in 1917, has since spread, and can now be observed throughout Europe as well as on other continents like Northern and Southern America, Asia and Africa. The PPV is infectious to European and Japanese plum as well as to apricot and peach. Infected plants show yellow ring spots and distortions on leaves and fruits. Fruits show pockmarked indentations, and strong premature drop of fruit occurs frequently. So far, there are no effective control measures against Sharka disease and the applied strategies are of preventive nature. Therefore, breeding new Sharka-tolerant/resistant varieties that either do not show symptoms at all or have a strong hypersensitive response against the pathogen is a very important goal. This is challenging, as only few cultivars were found that show resistance to the Sharka disease. In addition, the hexaploid genome of the European plum Prunus domestica L. limits progress in breeding. In order to increase effective selection in breeding populations, we aim to identify genomic regions that can be associated with Sharka resistance. This will be achieved by using a segregating F₁ population as well as a set of breeding clones that show variable strengths of the hypersensitive response. Finally, we aim to develop molecular markers that will facilitate breeding European plum cultivars that are less susceptible to Sharka disease.