NATURAL DIFFUSION AND EXPERIMENTAL TRANSMISSION OF PLUM “LEPTONECROSIS”(*)

Plum trees of the Japanese varieties Ozark Premier and Shiro, planted in 1983, together with trees of four European plum varieties, in an experimental field, located in an area of the Friuli-Venezia Giulia Region (Gemona) where plum leptonecrosis disease (PLN) is present, showed the typical symptoms of the disease starting from 1985; no symptom was observed on the European varieties.
On Ozark Premier trees symptoms were heavier and some of them died, starting from the second year.

Ozark Premier bite-plants planted close to affected trees in the Gemona and in a second experimental field in Udine, isolated and where apparently healthy plum trees were present, showed PLN symptoms starting from the first year.
In a mapped Ozark Premier commercial orchard, 42% of the trees were showing symptoms by the second year after planting.

Graft transmissions on potted Ozark Premier young trees and GF 305 peach seedlings grown in the greenhouse and on trees in the field were highly successful.
Symptoms were shown also by the sprouts of Ozark Premier scions topgrafted on myrabolan suckers coming from the rootstock of affected plum trees, rooted in pots in the greenhouse.

Up to now, in spite of the evident natural spread of the disease, no positive result was obtained in transmission trials using several species of leafhoppers captured in the field and fed for different periods of time on PLN affected plum trees.

DAPI test and electron microscope observations proved that MLOs are present in the leaf and root tissues of the affected plum trees.
In ultrathin sections many alterations were detected in the affected tissues.

XV International Symposium on Fruit Tree Diseases

L. Carraro, R. Osler, E. Refatti, M.A. Favali

https://doi.org/10.17660/ActaHortic.1992.309.41