Phytoplasmas: diversity, taxonomy, and epidemiology

Abstract

Phytoplasma associated diseases are spread worldwide, and in several cases are associated with severe epidemic of very often quarantine importance. These plant pathogens are prokaryotes belonging to the Mollicutes class since they lack a cell wall; up to now they were not cultivated in axenic culture therefore Koch postulates are only sometimes fulfilled by using alternative tools, such as graft or insect transmission. The possibility to design specific primers for highly conserved genes such as 16S ribosomal gene together with the use of molecular probes randomly cloned from phytoplasma genome, allowed discriminating and molecularly classifying them. Now a certain amount of knowledge is available that allow starting epidemiological studies in order to prevent further spreading of phytoplasma-associated diseases. In this paper molecular, biological and epidemiological characteristics of phytoplasma associated with important diseases worldwide are described.

cDNA-AFLP analysis of gene expression changes in apple trees induced by phytoplasma infection during compatible interaction

“…Phytoplasma diseases occur worldwide; very often associated with economically important plant diseases including coconut lethal yellowing, peach X-disease, and apple proliferation (AP) (Bertaccini 2007).…”

Polymerase Chain Reaction for Phytoplasmas Detection

“…However the suitability of most of the molecular methods depends closely on the amount of phytoplasma cells or nucleic acid in the extract. Approximately, 1% of phytoplasma DNA is extracted from tissue of total DNA (20). Since the concentration of this phloem-inhabiting pathogens is subjected to significant variations according to season (151), and is very low especially in woody hosts (79,88), the importance of obtaining phytoplasma DNA at a concentration and purity high enough for precise analysis is aparent.…”

Survey for Little Leaf of Brinjal Disease (Candidatus phytoplasmatrifolii) Incidence in Northern Karnataka, India

“…The insect vector, Hishimonus phycitis Distant was reported by (Bindra and Singh, 1969). Plants infected with phytoplasmas exhibit symptoms suggesting a profound disturbance in the normal balance of growth regulators, leading to virescence/ phyllody i.e., development of green leaf-like structures instead of flowers, sterility of flowers, proliferation of axillary buds resulting in -witches broom‖ symptoms, abnormal internode elongation and generalized stunting (Bertaccini, 2007). Phytoplasmas are transmitted by insects belonging to the families' viz., Cicadellidae, Cixidae, Psyllidae, Delphacidae and Derbidae (Weintraub and Beanland, 2006).…”