UPDATING AND EXTENDING GENETIC CHARACTERIZATION AND CLASSIFICATION OF PHYTOPLASMAS FROM WILD AND CULTIVATED PLANTS IN SOUTHERN ITALY

Abstract

Restriction fragment length polymorphism (RFLP), sequence analysis of PCR-amplified ribosomal DNA and chromosome size determination by pulsed-field gel electrophoresis (PFGE) were used to characterize phytoplasmas associated with diseases of wild and cultivated plants in southern Italy. The diseases examined were known, but not the identity of the pathogens, their incidence in southern Italy, or their genome sizes. The phytoplasma detected in Dimorphotheca sinuata (Cape marigold) was identified by RFLP analysis as a member of the pigeon pea witches’-broom (PPWB) group and proved to be indistinguishable from the picris echiodes yellows (PEY) reference strain. However, it differed from PEY in genome size. Phytoplasmas infecting Cape marigold have not previously been characterized. The phytoplasma detected in diseased Taraxacum officinale (dandelion) showed the same RFLP profiles as the picris echioides phyllody (PEP) reference strain of the Italian alfalfa witches’-broom (IAWB) group. Members of this group were not previously known to occur in dandelion. The phytoplasmas detected in diseased tobacco, pepper, celery and grapevine were indistinguishable, on the basis of rDNA profiles, from the stolbur phytoplasma strain (STOL). The phytoplasmas in diseased tobacco and pepper were characterized for the first time in Italy. Sequence analysis of the 16S rDNA confirmed that the knautia phyllody phytoplasma (KAP) is a member PPWB group and is closely related to PEY. Chromosome sizes from 785 to 1020 kb were found for the phytoplasmas associated with diseases of Cape marigold, French hydrangea, onion, field bindweed and tomato.