CHAPTER 2: Dissecting the Multifaceted Mechanisms That Drive Leafhopper Host–Phytoplasma Specificity

Abstract

HomeGeneral Plant PathologyVector-Mediated Transmission of Plant PathogensCHAPTER 2: Dissecting the Multifaceted Mechanisms That Drive Leafhopper Host–Phytoplasma Specificity PreviousNext CHAPTER 2: Dissecting the Multifaceted Mechanisms That Drive Leafhopper Host–Phytoplasma SpecificityAssunta Bertaccini, Kenro Oshima, Shigeyuki Kakizawa, Bojan Duduk, and Shigetou NambaAssunta BertacciniSearch for more papers by this author, Kenro OshimaSearch for more papers by this author, Shigeyuki KakizawaSearch for more papers by this author, Bojan DudukSearch for more papers by this author, and Shigetou NambaSearch for more papers by this authorAffiliationsAuthors and Affiliations Published Online:15 Nov 2016https://doi.org/10.1094/9780890545355.002AboutSectionsPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Abstract The discovery of a new group of plant pathogens related to bacteria more than 40 years ago led to the detection of pleomorphic, wall-less prokaryotes in the phloem of many plant species affected by yellows-type diseases. Plants infected by phytoplasmas exhibit an array of symptoms that suggest profound disturbances in the normal balance of growth regulators. These symptoms include virescence and phyllody (the development of green, leaflike structures instead of flowers), sterility of flowers, proliferation of axillary buds resulting in the development of witches’-brooms, abnormal internode elongation, and generalized stunting. These microorganisms are transmitted in a persistent and propagative manner by insects belonging to the families Cicadellidae, Cixiidae, Psyllidae, Delphacidae, and Derbidae. At the time of their discovery, phytoplasmas were difficult to detect because of their low concentrations, especially in woody hosts, and their erratic distribution in the sieve tubes of the infected plants. Observation by electron microscopy was the only diagnostic technique available until staining with DNAspecific dyes such as DAPI was developed. Later, protocols for the production of enriched phytoplasmaspecific antigens were developed, thus introducing serological detection techniques for the study of these pathogens in plants and insect vectors. Phytoplasmas are now routinely detected by different nucleic acid techniques based on polymerase chain reaction (PCR). The procedures developed since the 1990s are adequate for detecting phytoplasmas in plant propagation material and identifying insect vectors, thus helping in preventing the spread of the diseases and reducing their economic impact. The taxonomy of phytoplasmas is still in progress. It is based mainly on their grouping and subgrouping according to 16S rDNA gene identity, on which ‘Candidatus Phytoplasma’ species are also based. The list of described phytoplasma taxa was updated, but more ‘Candidatus species’ have been described. Key concepts included in this chapter: Historical Background Mechanism of Insect–Host Specificity of Phytoplasmas: Interactions Between a Phytoplasma Membrane Protein and Microfilaments of Insects Relationship Between Insect Transmission and Phytoplasma Plasmids Transovarial Transmission of Phytoplasmas DetailsFiguresLiterature CitedRelated Vector-Mediated Transmission of Plant PathogensISBN:978-0-89054-535-5 Metrics Pages: 21-28 InformationPDF download