First report of a γ 3-proteobacterium associated with diseased strawberries in Italy.

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 Abstract, repliche, brevi interventi e simili (Pubblicazione in rivista) [visualizza] [autori riconosciuti] id: 0064210 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..