A New Disease in Limonium hybrids. I. Molecular Identification

Yellows diseases in ornamental crops have become more common in Israel, and phytoplasmas have been detected in several crops. Recently, symptoms typical of a phytoplasma infection were observed on a large number of Limonium hybrids grown in commercial fields in Israel. Examination of samples from diseased plants by electron microscopy revealed the presence of pleiomorphic membrane-bound bodies in the phloem cells. Diseased plants were additionally analyzed by PCR using universal and nested primers and revealed upon sequencing products of 1143, 788 and 722 bp (Li-IL, Li-b2-IL, Li-v3-IL, respectively). Analysis of the PCR products, associated with infected Limonium, clustered within two major groups of phytoplasmas (16SrV and 16SrIX), elm yellows and almond witches broom. This is the first published record of these phytoplasmas in Israel.

‘Candidatus Phytoplasma spartii’, ‘Candidatus Phytoplasma rhamni’ and ‘Candidatus Phytoplasma allocasuarinae’, respectively associated with spartium witches'-broom, buckthorn witches'-broom and allocasuarina yellows diseases

Spartium witches'-broom (SpaWB), buckthorn witches'-broom (BWB) and allocasuarina yellows (AlloY) are witches'-broom and yellows diseases of Spartium junceum (Spanish broom), Rhamnus catharticus (buckthorn) and Allocasuarina muelleriana (Slaty she-oak), respectively. These diseases are associated with distinct phytoplasmas. The SpaWB, BWB and AlloY phytoplasmas share <97·5 % 16S rDNA sequence similarity with each other and with other known phytoplasmas, including the closely related phytoplasmas of the apple proliferation group. Also, the SpaWB, BWB and AlloY phytoplasmas each have a different natural plant host. Based on their unique properties, it is proposed to designate the mentioned phytoplasmas as novel ‘Candidatus’ species under the names ‘Candidatus Phytoplasma spartii’, ‘Candidatus Phytoplasma rhamni’ and ‘Candidatus Phytoplasma allocasuarinae’, respectively.