Abstract
Phytoplasmas are a special group of phloem-living pathogens in several plant species. Grapevine yellows (GY) is a term for phytoplasma diseases occurring on Vitis vinifera and inducing the same or very similar symptoms and causing severe losses worldwide. Flavescence Dorée (16SrV) phytoplasma (FD, species name: ‘Candidatus Phytoplasma vitis’) is considered a quarantine pest in several countries due to its epidemic character and high economic loss it provokes. The leafhopper Scaphoideus titanus is the univoltine and monophagous vector of FD. Bois noir disease caused by stolbur (16SrXII-A) phytoplasma (species name: ‘Candidatus Phytoplasma solani’) is described under different disease names in different countries. Hyalesthes obsoletus (Cixiidae) is the only proved polyphagous vector of BN. However, distribution of BN disease is increasing also on those areas where H. obsoletus is not prevalent or only in a very low number. Therefore the presence of other vectors cannot be concluded. The ‘Tuf-a’ type Stolbur phytoplasma is associated with stinging nettle (Urtica dioica) and the tuf-b type one to field bindweed (Convolvulus arvensis). There are only preventive control measures against phytoplasmas: the use of pathogen-free propagating material, hot water treatment of propagating material, as well as control of vectors and weeds. S. titanus can be efficiently controlled by insecticide treatments. However, in case of H. obsoletus, insecticides are not effective due to the biological characters and feeding habits of the vector.Weed control can reduce H. obsoletus specimen and their abundance to a certain extent. Extensive research is needed on wild hosts of GY phytoplasmas especially on BN phytoplasma and its vectors to the better understanding of their epidemiology.
Highlights
Grapevine yellows (GY) is a term for all the phytoplasma diseases occurring on Vitis vinifera cultivars on different continents
Flavescence Dorée (FD) was the first GY disease described by Caudwell (1957) in France
Flavescence dorée (FD) phytoplasma is transmitted from grapevine to grapevine only by Scaphoideus titanus Ball (Homoptera, Cicadellidae), the American grapevine leafhopper in a persistent manner
Summary
Phytoplasmas, the gram-positive bacterial pathogens inducing yellows and witches’ broom type diseases on different crops and causing devastating yield losses, are worldwide distributed. Doi et al (1967) discovered structures in ultrathin sections of the phloem of plants affected by these diseases These agents had no rigid cell walls, they were surrounded by a single cell membrane, their shape was spherical or pleomorphic and their size ranges were similar to those of mycoplasmas (80–800 nanometres). Phytoplasmas are obligate parasites of plants and insects; their life cycle involves replication in both of them They live and multiply only in the phloem sieve tube elements of the plants. Detailed studies are being conducted by several research groups in different countries for the better understanding of the interactions of phytoplasmas with their insect vectors and host plant species, as well as the investigations are in progress for the exploration of the exact mechanisms of symptom development and the genes that control these events (Bertaccini & Duduk 2009)
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