Molecular and serological approaches in detection of phytoplasmas in plants and insects

The impact of phytoplasmas in agriculture has become serious, and early diagnosis is the best option to prevent the disease spread. Very often the symptoms-based diagnostics is not sufficient or able to discriminate among the diverse phytoplasmas. Until the early 1980s, the phytoplasma presence in diseased plants was detected by transmission electron microscopy observation, and DAPI staining that was developed to detect the pathogen under fluorescent microscopy. Enzyme-linked immunosorbent assay (ELISA) was rarely used since the antisera were developed only for a few phytoplasma-associated diseases. Around 1990, advances in molecular biology enabled direct detection of phytoplasma DNA by hybridization and polymerase chain reaction technologies. PCR amplification of the 16S rRNA genes of phytoplasmas has become the key in phytoplasma disease detection, and now, several variants of PCR like nested and quantitative PCR, microarrays, and NGS are used for detection of phytoplasmas in both plants and insects. The approach using RFLP analyses and or sequencing of PCR-amplified 16S rDNA fragments provides a simple, reliable, and rapid mean for differentiation and identification of known phytoplasma strains. In this chapter up-to-date accounts of developments in serological and molecular approaches for the phytoplasma identification in plants and insect vectors are summarized.