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Molecular characterization of stolbur phytoplasma infecting weeds, vegetables and grapevine, based on vmp1 gene variability.
No full textFirst report of a γ 3-proteobacterium associated with diseased strawberries in Italy.
No full textDuring the fall seasons of 2005 and 2006, diseased strawberry plants (Fragaria × ananassa Duch.) were observed in nurseries and production fields in Ferrara, Forli-Cesena, and Ravenna provinces (Emilia-Romagna region, northern Italy). Symptoms consisted of a conspicuous plant stunting with a poor root system. Older leaves rolled upward and displayed a marked premature purplish discoloration, while young leaves were cupped, chlorotic, generally reduced in size, and had shortened petioles. This strawberry disorder was similar to “marginal chlorosis”, an infectious disease occurring in France that can be induced by two different phloem-limited uncultured bacteria: the γ 3-proteobacterium ‘Candidatus Phlomobacter fragariae’ and the stolbur phytoplasma (16SrXII-A). In strawberry production fields, ‘Ca. P. fragariae’ is reported as being the prevalent agent of this disease (1). Sixty-seven diseased plants were collected from production fields and nurseries for testing for ‘Ca. P. fragariae’. Leaf samples were analyzed by 4′,6-diamidine-2-phenylindole staining and PCR. Forty samples showed fluorescent DNA in the phloem, whereas no fluorescence was observed in symptomless strawberries. When tested by PCR with primers Fra4/Fra5, which amplify a 550-bp fragment of the 16S rDNA region of ‘Ca. P. fragariae’ (1), 13 of 36 strawberries from production fields and 1 of 31 nursery plants gave a positive reaction. On the other hand, 21 samples from nurseries and 5 from production fields tested positive for stolbur phytoplasma (3). No amplification was obtained with DNA from symptomless or healthy Abstract, repliche, brevi interventi e simili (Pubblicazione in rivista)
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Abstract
During the fall seasons of 2005 and 2006, diseased strawberry plants (Fragaria × ananassa Duch.) were observed in nurseries and production fields in Ferrara, Forli-Cesena, and Ravenna provinces (Emilia-Romagna region, northern Italy). Symptoms consisted of a conspicuous plant stunting with a poor root system. Older leaves rolled upward and displayed a marked premature purplish discoloration, while young leaves were cupped, chlorotic, generally reduced in size, and had shortened petioles. This strawberry disorder was similar to “marginal chlorosis”, an infectious disease occurring in France that can be induced by two different phloem-limited uncultured bacteria: the γ 3-proteobacterium ‘Candidatus Phlomobacter fragariae’ and the stolbur phytoplasma (16SrXII-A). In strawberry production fields, ‘Ca. P. fragariae’ is reported as being the prevalent agent of this disease (1). Sixty-seven diseased plants were collected from production fields and nurseries for testing for ‘Ca. P. fragariae’. Leaf samples were analyzed by 4′,6-diamidine-2-phenylindole staining and PCR. Forty samples showed fluorescent DNA in the phloem, whereas no fluorescence was observed in symptomless strawberries. When tested by PCR with primers Fra4/Fra5, which amplify a 550-bp fragment of the 16S rDNA region of ‘Ca. P. fragariae’ (1), 13 of 36 strawberries from production fields and 1 of 31 nursery plants gave a positive reaction. On the other hand, 21 samples from nurseries and 5 from production fields tested positive for stolbur phytoplasma (3). No amplification was obtained with DNA from symptomless or healthy strawberry plants. Sequencing Fra4/Fra5 amplicons from three samples (GenBank Accession Nos. DQ362916–DQ362918) showed a 98.1 to 98.6% and a 98.3 to 98.8% identity with the published sequences of the French isolate “LG2001” (GenBank Accession No. AM110766) and the Japanese isolate J-B (GenBank Accession No. AB246669) of ‘Ca. P. fragariae’, respectively. Higher homology (99.2 to 99.8%) was found with another bacterium-like organism (BLO) of the γ 3-proteobacteria subgroup (GenBank Accession No. AY057392) associated with the syndrome “basses richesses” of sugar beet (SBR). Furthermore, PCR assays performed with..
Molecular characterization of grapevine Bois noir phytoplasma in central-southern Italian regions
No full textGenetic variability of the stolbur phytoplasma vmp1 gene in grapevines, bindweeds and vegetables. Corrigendum
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Genetic variability of the stolbur phytoplasma vmp1 gene in grapevines, bindweeds and vegetables. Corrigendum
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Molecular characterization of grapevine Bois noir phytoplasma in central-southern italian regions.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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