Phytoplasma diseases of grapevine and the possible measures to control them

Phytoplasmas are a special group of phloem-living pathogens in several plant species. Grapevine yellows (GY) is a term forphytoplasma 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 severalcountries due to its epidemic character and high economic loss it provokes. The leafhopper Scaphoideus titanus is the univoltine andmonophagous 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 ofBN. 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 (Urticadioica) and the tuf-b type one to field bindweed (Convolvulus arvensis). There are only preventive control measures against phytoplasmas: theuse of pathogen-free propagating material, hot water treatment of propagating material, as well as control of vectors and weeds. S. titanus canbe efficiently controlled by insecticide treatments. However, in case of H. obsoletus, insecticides are not effective due to the biologicalcharacters and feeding habits of the vector.Weed control can reduce H. obsoletus specimen and their abundance to a certain extent. Extensiveresearch is needed on wild hosts of GY phytoplasmas especially on BN phytoplasma and its vectors to the better understanding of theirepidemiology

Phytoplasma diseases of grapevine and the possible measures to control them

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

Presence of stolbur phytoplasma in Cixiidae in Hungarian vineyards

Bois Noir (16SrXII-A) phytoplasmas were identified in three viticultural areas of Hungary in 18 % of Hyalesthes obsoletus, and in an asymptomatic nettle sample. The cixiid Reptalus panzeri was found to be infected with 16SrXII-A and with 16SrIII (X-disease) phytoplasmas. The latter pathogen was also detected in symptomatic wild Cirsium spp. and Convolvolus collected inside Bois Noir-infected and R. panzeri-infested vineyards

Certification programme for production of virus-free propagating material of grapevine and its results in Hungary

In Hungary, detection of virus and virus-like diseases of grapevine began in 1960's at the Research Institute for Viticulture and Enology by János Lehoczky and his colleagues. At present, sixteen virus and virus-like diseases of Vitis vinifera are known to occur in Hungary. Regular virological screening of grapevine varieties started in 1972. The present system of screening (visual selection, indexing, ELISA) has been established using methods with continuous improvement according to recommendations of international organizations. In the first year symptomless grapevine plants are selected and marked during surveys carried out twice in the vegetation period: at about flowering and in the second half of September. At the first selection time plants are sampled for ELISA. In the spring of the second year, overwintered canes are checked by woody indexing on 8 indicator species in the field. In the third and fourth years the nursery is evaluated twice again. At the end, the marked grapevine plants, giving negative results on all indicators in every case, are considered virus-free. In autumn of the fourth year, the virus-free material is planted out under screenhouse and also in a special mother block (nuclear stock) for maintenance and propagation. Mother blocks of virus-free scion varieties have been established on 2 ha and those of rootstock varieties on 0.5 ha planted with the following number of varieties included in the national list: 71 European scion — and 12 rootstock varieties or variety candidates/clones. It is necessary to increase the area of Pre-base, Base and Certified stocks exclusively with tested virus-free (clean) material

Detection and identification of phytoplasmas in peach based on woody indexing and molecular methods

Symptoms resembling phytoplasma disease have been observed on peach trees in a seed-source plantation of stone fruits in south Hungary quite recently. In this publication we report on the results of woody indexing of symptomatic peach trees on GF 305 indicator in the field and under greenhouse conditions as well as on molecular studies. Phytoplasma infection detected on GF 305 indicators in greenhouse and field indexing was confirmed by PCR. Nested PCR was conducted using universal primer pairs followed by group and subgroup specific primers for the second amplification. RFLP analysis of nested PCR products was performed using Rsal restriction enzyme. Based on the results of molecular studies it can be concluded that phytoplasmas, belonging to the European stone fruit yellows subgroup (16SrX-B) were identified in peach trees. Further studies on symptomatic peach trees originating from different parts of Hungary are in progress

Certification programme for production of virus-free propagating material of grapevine and its results in Hungary

In Hungary, detection of virus and virus-like diseases of grapevine began in 1960's at the Research Institute for Viticulture and Enology by János Lehoczky and his colleagues. At present, sixteen virus and virus-like diseases of Vitis vinifera are known to occur in Hungary. Regular virological screening of grapevine varieties started in 1972. The present system of screening (visual selection, indexing, ELISA) has been established using methods with continuous improvement according to recommendations of international organizations. In the first year symptomless grapevine plants are selected and marked during surveys carried out twice in the vegetation period: at about flowering and in the second half of September. At the first selection time plants are sampled for ELISA. In the spring of the second year, overwintered canes are checked by woody indexing on 8 indicator species in the field. In the third and fourth years the nursery is evaluated twice again. At the end, the marked grapevine plants, giving negative results on all indicators in every case, are considered virus-free. In autumn of the fourth year, the virus-free material is planted out under screenhouse and also in a special mother block (nuclear stock) for maintenance and propagation. Mother blocks of virus-free scion varieties have been established on 2 ha and those of rootstock varieties on 0.5 ha planted with the following number of varieties included in the national list: 71 European scion — and 12 rootstock varieties or variety candidates/clones. It is necessary to increase the area of Pre-base, Base and Certified stocks exclusively with tested virus-free (clean) material

Detection and partial molecular characterization of Plum pox virus on almond trees in Turkey

Almond (Prunus dulcis) is one of the well known stone fruit species grown for its unripe fruits and delicious seeds in Turkey. In the Trakya region, however, some prevailing virus infections have reduced almond yields and quality. In ten districts of Trakya, 260 leaf samples were collected from affected almond trees in June 2010. DAS-ELISA assays and RT-PCR tests were employed for the identification of viruses. As a result of these detection studies, five of the 260 leaf samples gathered from symptomatic almond trees had Plum pox virus (PPV), 81 of them had Prunus necrotic ringspot virus (PNRSV), and 11 samples contained Prune dwarf virus (PDV). Only four out of 260 samples had a mixture of these viruses. Partial nucleotide sequences of five almond isolates of PPV were determined and compared with 17 other PPV isolates in databases. Computer analysis of obtained and published nucleotide sequences showed identity ranged from 75.72% to 96.87%. Of the five PPV almond isolates obtained, however, there was a close nucleotide identity of 95.82-96.61% to Turkish isolates. Phylogenetic analysis of nucleotides and amino acids showed that five PPV isolates of almond from the Trakya Region of Turkey were clustered in the same subgroup with PPV-T Turkish isolates in GenBank. Therefore we can consider almond isolates of PPV as PPV-T strain, like the two other isolates from apricot trees in Turkey