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Alder yellows (ALY) phytoplasma (16SrV-C) is associated with ALY, a disease of several Alnus (alder) species in Europe and A. rubra in North America. In all affected species, the symptoms are similar. However, latent infections are common. ALY phytoplasma includes different strains which may be occasionally transmitted to grapevines leading to some grapevine yellows diseases. In the current study, visual symptom assessment and PCR-based methods using universal and group-specific phytoplasma primers were used to update and extend knowledge on the occurrence, impact, and genetic diversity of ALY phytoplasma in declining and non-symptomatic A. glutinosa and A. cordata trees in the Basilicata and Campania regions of southern Italy. ALY phytoplasma was detected in 80% of alder trees examined. In symptomatic trees, no other cause of disease was observed. More than half of alder trees that tested phytoplasma-positive proved to be latently infected. A considerable genetic variability was observed among the newly recorded ALY phytoplasma strains in southern Italy in almost of the genes examined. These included 16S rRNA, 16S/23S rDNA spacer region, ribosomal protein rpsV (rpl22) and rpsC (rps3), map, imp, and groEL genes. Eleven new genotypes were identified at map gene sequence level. However, the genetic differences observed were not related to plant host species, geographical origin, and symptoms shown by infected alder trees. Also, this study indicates that ALY phytoplasma is more widespread than previously thought. [ABSTRACT FROM AUTHOR]

Alder yellows (ALY) phytoplasma (16SrV-C) is associated with ALY, a disease of several Alnus (alder) species in Europe and A. rubra in North America. In all affected species, the symptoms are similar. However, latent infections are common. ALY phytoplasma includes different strains which may be occasionally transmitted to grapevines leading to some grapevine yellows diseases. In the current study, visual symptom assessment and PCR-based methods using universal and group-specific phytoplasma primers were used to update and extend knowledge on the occurrence, impact, and genetic diversity of ALY phytoplasma in declining and non-symptomatic A. glutinosa and A. cordata trees in the Basilicata and Campania regions of southern Italy. ALY phytoplasma was detected in 80% of alder trees examined. In symptomatic trees, no other cause of disease was observed. More than half of alder trees that tested phytoplasma-positive proved to be latently infected. A considerable genetic variability was observed among the newly recorded ALY phytoplasma strains in southern Italy in almost of the genes examined. These included 16S rRNA, 16S/23S rDNA spacer region, ribosomal protein rpsV (rpl22) and rpsC (rps3), map, imp, and groEL genes. Eleven new genotypes were identified at map gene sequence level. However, the genetic differences observed were not related to plant host species, geographical origin, and symptoms shown by infected alder trees. Also, this study indicates that ALY phytoplasma is more widespread than previously thought.

Solidago microglossa (goldenrod) is a species with medicinal properties, generating products of estimable economic value, which are commercialized as medicines and cosmetics. Plants of S. microglossa exhibiting intense proliferation of small leaves, producing a compact canopy, were found sparsely in a field. Since these symptoms are indicative of infection by phytoplasmas, a survey was performed in order to understand the etiological cause of observed symptoms. The total DNA extracted from the tested plants was used in nested PCR primed by P1/16S-SR followed by R16F2n/R16R2. Leaf veins were appropriately prepared for visualization in transmission electron microscopy. The presence of phytoplasma was revealed in symptomatic samples by amplification of genomic fragments of 1.25 Kb. In agreement, phytoplasma cells were observed in the phloem vessels of these plants. Nucleotide sequences from the phytoplasma were indistinguishable among themselves and shared 99.7% identity with sequences of phytoplasmas belonging to the 16SrIII group. Computer-simulated RFLP and phylogenetic analysis classified the S. microglossa phytoplasma as member of the 16SrIII-X subgroup. In addition, the present study revealed S. microglossa as an additional host species for this phytoplasma. [ABSTRACT FROM AUTHOR]

Every year, in Italy many new cases of Flavescence dorée (FD) and Esca disease (ED) are recorded in Vitis vinifera , resulting in plant death and reduced production. FD is caused by phytoplasmas and its main symptoms comprise growth reduction, leaf reddening and downward rolling. The vines affected by ED, a fungal disease, show foliar inter-venal necrosis and chlorosis. The aim of this work was to test a commercial optical sensor for the detection of FD and ED in plants. Three vineyards of the red grapevine Dolcetto cv. were mapped and plants showing FD or ED symptoms were georeferenced. In July 2015 and 2016, monitoring by optical sensors (OptRx®) was undertaken and leaf samples from plants were collected to confirm the presence of FD phytoplasmas by molecular analyses. The OptRx® records the reflectance and calculates two indices: normalised difference vegetation index (NDVI) and normalised difference red edge index (NDRE). A visible/near infrared (VIS/NIR) index was calculated from the two reflectances. Data were processed by either statistical analysis of raw data, to detect differences in the plant health status and between the two years, or by using filters to evaluate sensitivity and specificity of the sensor in detecting the diseases and create prediction indices. Diseased plants showed lower NDVI and NDRE values than healthy plants. A negative signal from the filter system was always associated with healthy plants. Further studies are needed in order to understand the most appropriate threshold and to implement the diagnostic algorithm to assess the presence of disease. • Diseased plants showed lower values of NDVI and NDRE than healthy ones. • Diseased plants presented higher values of VIS/NIR compared to healthy ones. • Index absolute values were highly variable across vineyards and years. • A normalised moving average metric was used to detect problem areas in the vineyard. • The employed algorithm correctly classified all healthy plants. [ABSTRACT FROM AUTHOR]

This paper provides an updating of information of a selected number of major phytoplasma diseases of forest trees, with a focus on the associated phytoplasma taxa. Phytoplasma diseases of forest trees have been less extensively studied than those affecting fruit trees. Research on the role of phytoplasmas as the cause of diseases of forest trees has only in the last few years been intensified, after sensitive and specific detection methods greatly based on PCR technology became available. Various phytoplasma taxa have been identified in naturally infected elm, ash, conifer, sandal, and eucalyptus trees, whereas only one phytoplasma taxon has been recorded in naturally infected alder trees. However, for almost all of the reviewed diseases, there is still sparse information about insect vectors, plant host range, strain virulence, pathogenicity, and host tolerance and resistance. Knowledge of these aspects is the basis for appropriate disease management. In particular, further research is required to clarify the role of phytoplasmas in asymptomatic trees. In addition, the etiological role of various “non-specific” phytoplasma taxa, which have been recorded in forest trees, while no data from pathological studies are available, needs to be further investigated.

Medicinal and aromatic plants include a broad array of wild and cultivated plants which contain many biologically-active compounds, known as phytochemicals, that are of great interest for their ability to promote human and animal health. The present review provides a literature overview of phytoplasma diseases affecting medicinal and aromatic plants, with an emphasis on phytoplasma taxa associated. An overview of studies that examined the effect of phytoplasma infections on phytochemical content and other secondary metabolites of affected plants is also included. Phytoplasma diseases of medicinal and aromatic plants occur worldwide; however, the majority of reports are from Europe and southeastern Asian countries. These diseases affect plant species belonging to over 70 families, mostly to Apiaceae and Asteraceae. They differ considerably in geographic distribution and size of the various taxonomic groups and subgroups of the associated phytoplasmas. Subgroup 16SrI-B phytoplasmas are the prevalent agents occurring mainly in Europe, North America and Asia. Phytoplasma presence induces changes in the amount and composition of secondary metabolites in diseased plants in which, however, the concentrations of valuable phytochemicals are greatly affected. An exception is represented by phytoplasma diseases of periwinkle in which an accumulation of pharmaceutically important compounds occurs upon phytoplasma infections. Prospects for future research are presented and critically discussed. [ABSTRACT FROM AUTHOR]

Tomato plants displaying foliar chlorosis, shoot proliferation, calyx deformation and reduced leaves, flowers and fruits all symptoms of tomato big bud, were found in a culture at Bragança Paulista region, State of São Paulo, Brazil. Samples were collected and analyzed by electron microscopy, PCR and RFLP to detect and identify the possible phytoplasma associated with diseased plants. Pleomorphic and round corpuscles were observed in the phloem vessels of diseased plants; the presence of phytoplasma was confirmed by PCR using universal primer pairs. PCR assays primed by group-specific primer pairs enabled the identification of the detected phytoplasma as a member of the 16SrIII group. Molecular identification by RFLP using various endonucleases confirmed the classification of this phytoplasma as a representative of the 16SrIII group. Phytoplasmas that are associated with big bud have been classified in different groups. The big bud phytoplasma identified in Brazil belongs to the same group of phytoplasmas associated with tomato big bud in Italy, but it is different from those found in other areas of the world. [ABSTRACT FROM AUTHOR]

A disease of Melaleuca armilaris (Myrtaceae) plants, belonging to the yellows group of diseases, is described from Israel. The disease was associated with bacteria-like organisms (BLO) occurring in growing tips. The BLO were observed in both xylem and phloem tissues. Electron microscope observations demonstrated that the overall number of cells invaded by BLO in winter, when seen best, was relatively small. BLO diameter was 400 to 650 nm and length was 950 to 1400 nm. [ABSTRACT FROM AUTHOR]

This paper provides an updating of information of a selected number of major phytoplasma diseases of forest trees, with a focus on the associated phytoplasma taxa. Phytoplasma diseases of forest trees have been less extensively studied than those affecting fruit trees. Research on the role of phytoplasmas as the cause of diseases of forest trees has only in the last few years been intensified, after sensitive and specific detection methods greatly based on PCR technology became available. Various phytoplasma taxa have been identified in naturally infected elm, ash, conifer, sandal, and eucalyptus trees, whereas only one phytoplasma taxon has been recorded in naturally infected alder trees. However, for almost all of the reviewed diseases, there is still sparse information about insect vectors, plant host range, strain virulence, pathogenicity, and host tolerance and resistance. Knowledge of these aspects is the basis for appropriate disease management. In particular, further research is required to clarify the role of phytoplasmas in asymptomatic trees. In addition, the etiological role of various "non-specific" phytoplasma taxa, which have been recorded in forest trees, while no data from pathological studies are available, needs to be further investigated. [ABSTRACT FROM AUTHOR]