Phytoplasmas: detection, differentiation and classification, and relationships with plant and insect hosts - April 2012

Plant-pathogenic phytoplasmas are wall-less, unculturable bacteria of the class Mollicutes that are associated with diseases in more than a thousand plant species worldwide and are transmitted in nature by phloem-feeding homopteran insects, mainly leafhoppers and planthoppers, and less frequently psyllids. By the introduction of DNA-based methods into phytoplasmology about two decades ago, specific and sensitive detection methods have been developed, mainly based on polymerase chain reaction (PCR) assays. It also became possible to differentiate, characterize and classify phytoplasmas on a phylogenetic basis, using sequence and restriction fragment length polymorphism (RFLP) analysis of 16S ribosomal DNA (rDNA). Recently, multi-locus sequence analysis employing genes with varying degrees of genetic variability revealed new insights into the genetic diversity of phytoplasmas that are relatively homogeneous at 16S rDNA sequence level. The numerous papers published over the last few years in Annals of Applied Biology, reflect the tremendous progress made in differentiation and classification, and also in detection and identification of phytoplasmas in both plants and insects. Annals of Applied Biology also published a number of papers on phytoplasma-insect vector relationships, newly reported phytoplasma diseases, colonization behavior of phytoplasmas in plants, a pathogen eradication method useful to produce healthy plant materials, and etiological elucidation of decline diseases supposed to be induced by phytoplasmas. Some of the mentioned papers are highlighted below.