Detection of phytoplasmal DNA in flowers and seeds from elm trees infected with Elm Yellows

The occurrence of phytoplasmas associated with Elm Yellows (EY) was investigated in the reproductive structures (flowers, unripe and ripe fruits) of two EY-infected trees of the hybrid elm clone Lobel and two healthy trees, an Ulmus laevis and an U. japonica. Phytoplasma group-specific Polymerase Chain Reaction (PCR), restriction fragment length polymorphism analysis and sequencing of amplified fragments were carried out using as template DNA extracted from these reproductive structures. The flowers and fruits were dissected into parts (the flowers into anthers and ovaries, the fruits into seeds and membranaceous wings), and then examined separately. A total of 350 seeds from infected trees were sown, producing 24 plantlets, which were sampled for EY phytoplasma DNA one and five months after germination. Both flowers and seeds from the EY-infected trees were good sources for the extraction and PCR-amplification of EY phytoplasmas, but no EY phytoplasmas were detected in either the flowers and seeds of the two healthy trees or in samples collected from the 24 plantlets grown from seed

Phytoplasmas, Aceria bezzii and drought in declining European hackberry (Celtis australis L.)

Growth abnormalities and decline of hackberry trees have been reported throughout the Mediterranean growth area of the species for over 50 years. Recently, the presence of phytoplasmas belonging to aster yellows and elm yellows groups was detected by molecular techniques in both declining and asymptomatic hackberries. Symptoms of decline appear to be influenced by the amount of rainfall during early spring. In Italy hackberry trees are also infested by the eriophide mite Aceria bezzii (Corti) which kills most of the main, fertile buds causing delayed sprouting of adventitious, sterile buds and loss of fruit production. These three factors seem to interact in determining the sanitary status of this Ulmacea. The widespread phytoplasma presence seems to insidiously weaken trees, which clearly show stress symptoms in drought years, whereas mite infestation acts beneficiously on tree health by reducing the number of sprouting buds and fruit-set, and delaying burst of adventitious buds