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Tomato (Solanum lycopersicum) plants exhibiting symptoms resembling those of permanent yellowing disease (known in Mexico as “permanente del tomate”) that is commonly associated with phytoplasmas (1) were observed in tomato fields in Sinaloa, México in March 2009. Plant symptoms also resembled those caused by “Candidatus Liberibacter solanacearum” infection (2). Affected plants showed an overall chlorosis, severe stunting, leaf cupping, purple discoloration of veins, excessive branching of axillary shoots, and leaf scorching (1,2). Symptom incidence ranged from 18 to 40%. To investigate whether liberibacter is associated with permanent yellowing disease of tomato in México, eight symptomatic and five asymptomatic tomato plants were collected from two fields in La Cruz de Elota and Culiacán, Sinaloa. Total DNA was extracted from the top whole leaf tissue of symptomatic and asymptomatic plants with cetyltrimethylammoniumbromide (CTAB) buffer (3,4). DNA samples were tested by PCR using primer pairs OA2/OI2c and CL514F/CL514R, which amplify a sequence from the 16S rDNA and rplJ and rplL ribosomal protein genes, respectively, of “Ca. L. solanacearum” (2,4). The DNA samples were also tested for phytoplasmas with nested PCR using universal primer pairs P1/P7 and fU5/rU3 (3). DNA from five and four symptomatic plants yielded the expected 1,168-bp 16S rDNA and 669-bp rplJ/rplL amplicons, respectively, indicating the presence of liberibacter. Extracts from asymptomatic plants yielded no products with these primers. Amplicons generated from three symptomatic plants with each primer pair were cloned into pCRII-TOPO plasmid vectors (Invitrogen, Carlsbad, CA) and three clones of each of these amplicons were subsequently sequenced in both directions (ACGT, Inc., Wheeling, IL). BLAST analysis of the 16S rDNA consensus sequence (GenBank Accession No. FJ957897) showed 100% identity to 16S rDNA sequences of “Ca. L. solanacearum” amplified from S. betaceum (EU935004) and S. lycopersicum (EU834130) from New Zealand (2), and “Ca. L. psyllaurous” from potato psyllids (EU812559). The rplJ/rplL consensus sequence (GenBank Accession No. FJ957895) was 100% identical to the analogous rplJ and rplL “Ca. L. solanacearum” ribosomal protein gene sequence amplified from S. lycopersicum (EU834131) from New Zealand (2) and ‘Ca. Liberibacter’ sp. sequence amplified from zebra chip-infected potatoes from Lancaster, CA (FJ498803). No phytoplasmas were detected in the symptomatic tomato plants. To our knowledge, this is the first report of “Ca. L. solanacearum” associated with tomatoes in México. In 2008, this bacterium was detected in glasshouse tomatoes in New Zealand and caused millions of dollars in losses to the commercial glasshouse tomato industry (2). References: (1) R. L. Holguín-Peña et al. Plant Dis. 91:328, 2007. (2) L. W. Liefting et al. Plant Dis. 93:208, 2009. (3) J. E. Munyaneza et al. J. Econ. Entomol. 100:656, 2007. (4) J. E. Munyaneza et al. Plant Dis. 93:552, 2009.

In January of 2009, potato plants (Solanum tuberosum) from a commercial crop in the Waikato Region, New Zealand were observed to have symptoms of upward rolling and purpling of the leaves. The symptoms appeared similar to those of “zebra chip”, a disorder of potato recently found to be associated with ‘Candidatus Liberibacter solanacearum’ in New Zealand and the United States (4). Total DNA from the leaf midveins and tubers from one of the symptomatic plants was separately extracted with an InviMag Plant DNA Mini Kit (Invitek GmbH, Berlin, Germany) and a KingFisher mL workstation (Thermo Scientific, Waltham, MA). DNA extracted from leaf midveins and tubers tested negative for ‘Ca. L. solanacearum’ by nested-PCR using primer pair OA2/OI2c (4) followed by Lib16S01F/Lib16S01R (5′-TTCTACGGGATAACGCACGG-3′ and 5′-CGTCAGTATCAGGCCAGTGAG-3′), which amplifies a 580-bp region of the 16S rRNA gene. However, DNA extracted from the tuber tissue tested positive for phytoplasma by TaqMan real-time PCR (3). No phytoplasma was detected in the DNA extracted from leaf tissue. The 16S rRNA gene, 16S-23S rRNA intergenic spacer region, and part of the 23S rRNA gene of the phytoplasma were amplified with primers P1/P7 (1). The PCR product was cloned into the pCR 4-TOPO vector (Invitrogen, Carlsbad, CA) and sequenced (GenBank Accession No. FJ943262). BLAST analysis showed 100% identity to ‘Ca. Phytoplasma australiense’ (16SrXII, Stolbur group). A fragment of approximately 850-bp of the Tuf gene was also amplified (2) and sequenced directly (GenBank Accession No. FJ943263). BLAST analysis showed 100% identity to Tuf gene variant IX of ‘Ca. P. australiense’ (2). An additional 14 plants showing similar leaf symptoms and also production of aerial tubers were collected from seven different potato fields from the Auckland and Waikato regions. Total DNA from the leaf midveins, stem, and tubers were separately extracted from each of the plants. The samples were tested for phytoplasma by nested-PCR using primer pair R16F2/R16R2, followed by NGF/NGR (1), and tested for ‘Ca. L. solanacearum’ by nested-PCR as described above. Seven plants tested positive only for phytoplasma, three tested positive for only ‘Ca. L. solanacearum’, and four plants tested positive for both pathogens. The pathogens were most commonly detected in samples extracted from the stem with 9 and 5 of the 14 samples testing positive for phytoplasma and liberibacter, respectively. Six of each of the leaf and tuber samples tested positive for phytoplasma. Liberibacter was detected in one of the leaf samples and in four of the tuber samples. ‘Ca. P. australiense’ has only been reported from New Zealand and Australia. The only other known hosts of ‘Ca. P. australiense’ in New Zealand are strawberry and native plants belonging to the genera Cordyline, Coprosma, and Phormium (2). In Australia, ‘Ca. P. australiense’ is associated with Australian grapevine yellows and Papaya dieback (2). To our knowledge, this is the first report of ‘Ca. P. australiense’ infecting potato as well as the first report of phytoplasma and ‘Ca. L. solanacearum’ mixed infections in potato. References: (1) M. T. Andersen et al. Plant Pathol. 47:188, 1998. (2) M. T. Andersen et al. Phytopathology 96:838, 2006. (3) N. M. Christensen et al. Mol. Plant Microbe Interact. 17:1175, 2004. (4) L. W. Liefting et al. Plant Dis. 93:208, 2009.