Plant Disease

Sida is a genus of flowering herbs in the family Malvaceae, which includes several species that are weeds in Brazil. Plants of a Sida sp. exhibiting symptoms characterized by stunting, chlorosis, small leaves, and witches'-broom, indicative of infection by phytoplasmas, were found in a field previously cultivated with tomato, located in the region of Campinas, State of São Paulo, in December 2008. To demonstrate the presence of phytoplasmas in diseased tissues, DNA was extracted from shoots and leaves from three symptomatic and eight asymptomatic plants. Nested PCR was performed using primers P1/Tint followed by primer pair R16F2n/R16R2 (1). DNA fragments of 1.2 kb, corresponding to 16S rDNA, were amplified only for DNA from two symptomatic samples. Phytoplasma identification was initially carried out by restriction fragment length polymorphism (RFLP) analysis through digesting the PCR products with the restriction enzymes AluI, HhaI, HaeIII, HpaII, MseI, and RsaI. The two phytoplasma isolates found to be infecting a Sida sp. showed identical RFLP patterns, which were indistinguishable from the phytoplasma previously reported in association with hibiscus (Hibiscus rosa-sinensis) witches'-broom in Brazil (2). Nucleotide sequence alignment revealed that 16S rDNA of both phytoplasma isolates found in a Sida sp. (GenBank Accession No. HQ230579) shared 99.9% sequence similarity with 16S rDNA from hibiscus witches'-broom phytoplasma (HibWB) (GenBank Accession No. AF147708). HibWB is the representative of the 16SrXV group and it was proposed as a putative species nominated “Candidatus Phytoplasma brasiliense” (2). The disease is frequently observed in hibiscus plants used as ornamentals in the states of São Paulo (4) and Rio de Janeiro (2). “Ca. Phytoplasma brasiliense” has only been reported in Brazil to be infecting hibiscus (2,4) and periwinkle (Catharanthus roseus) (3). The presence of a phytoplasma belonging to group 16SrXV in a Sida sp. expands its natural host range. The role of this weed as a potential source of inoculum for crops should be investigated. References: (1) I. M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) H. G. Montano et al. Int. J. Syst. Evol. Microbiol. 51:1109, 2001. (3) H. G. Montano et al. Plant Dis. 85:1209, 2001. (4) E. G. Silva et al. Summa Phytopathol. 35:234, 2009.

Citrus huanglongbing, putatively caused by the associated bacterium ‘Candidatus Liberibacter asiaticus’, is the greatest threat to the world citrus industry today. The bacterium is spread locally and regionally by the citrus psyllid Diaphorina citri, and also can be disseminated by propagation of contaminated scion budwood that is grafted to the appropriate rootstock. The planting of ‘Ca. Liberibacter asiaticus’-free trees is a component of a comprehensive strategy to manage huanglongbing. In contrast to the scion budwood, the rootstocks used to produce these trees are grown from seed. This research was undertaken to provide evidence as to whether or not ‘Ca. L. asiaticus’ can be transmitted through seed. Two groups of 360 or more seedlings each of various citrus species were grown from seed removed from fruit on trees that were symptomatic for huanglongbing and confirmed to be infected with ‘Ca. L. asiaticus’ by polymerase chain reaction (PCR) tests. These seedlings were tested multiple times over periods of up to 3 years. No symptoms typical of huanglongbing, such as blotchy leaf mottle, chlorotic shoots, or dieback of branches, were observed in these seedlings, and none of these 723 seedlings tested positive for the presence of ‘Ca. L. asiaticus’ even after repeated testing by sensitive quantitative PCR assays. Some sour orange seedlings did have quite pronounced and atypical growth, including stunting and mild to severe leaf malformation. These atypical growth habits were limited to seedlings that arose from zygotic embryos as determined by expressed-sequence tag simple-sequence repeat analyses. Thus, no evidence of transmission of ‘Ca. L. asiaticus’ via seed was obtained, and an earlier report of transmission of the pathogen through seed was not confirmed.

Pelargonium capitatum (rose pelargonium) is a plant indigenous to southern Africa, originally brought to Western Australia for its ornamental qualities. It has since become naturalized in the Southwest Australian Floristic Region, recognized for its high level of species endemism, where it is a serious invasive weed in bushlands and coastal dunes. Since P. capitatum outcompetes native species it is listed among the top 10 most important coastal weeds of the region (3). In 2008, large patches of stunted, dying, and dead P. capitatum plants were observed within a population covering coastal dunes at Woodman Point, Western Australia (GPS coordinates 32°07′40.51″S, 115°45′28.39″E). Diseased plants had small misshapen leaves in clumps that were often chlorotic or pink, shortened internodes, and exhibited phylloidy typical of infection by a phytoplasma. From August 2009 to January 2010, samples from symptomatic and asymptomatic plants were collected from the site and from plants of an asymptomatic population at another site located on the Murdoch University campus nearby. DNA was extracted from 15 samples collected from symptomatic and asymptomatic plants at the dune site and from five at the campus site. Briefly, 2 to 5 g of leaf and stem tissue was cut into 5-mm pieces and shaken overnight in 30 ml of phosphate-buffered saline buffer. Supernatant was filtered and a pellet was collected by centrifugation. After resuspension in 500 μl of extraction buffer (200 mM Tris-HCl [pH 7.5] 250mM NaCl, 25mM ethylenediaminetetraacetic acid, 0.5% sodium dodecyl sulfate, and 2% polyvinylpyrrolidone), DNA was precipitated in 500 μl of cold isopropanol. Samples were tested for the presence of phytoplasma ribosomal 16S DNA by nested PCR using phytoplasma universal primers P1/P7 followed by amplification with primers Tint, R16mF2, and R16mR1 (1,2,4). Phytoplasma-specific DNA sequences were synthesized directly from amplicons using the above primers. Phytoplasma was detected from both symptomatic and asymptomatic plant samples collected from the dune site but not from the campus site. Analysis of the nine sequences obtained (GenBank Accession Nos. HM583339, HM583340, HM583341, HM583342, HM583343, HM583344, HM583345, HM583346, and HM583347) revealed high sequence identity between isolates (~99%) and with the ‘Candidatus Phytoplasma aurantifolia’ (16SrII) group of phytoplasmas (1,4). Presence of phytoplasma in symptomatic plants was confirmed by histological examination of stem sections stained with Dienes' stain. This finding is significant because there is potential for utilizing this phytoplasma to control P. capitatum where it has invaded ecologically significant sites, although its effect on indigenous plants must be determined first. Although phytoplasmas within the 16SrII group have been identified in Australia previously (1,4), to our knowledge, this is the first report of it infecting P. capitatum. References: (1) K. S. Gibb et al. Phytopathology 85:169, 1995. (2) D. E. Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (3) B. M. J. Hussey et al. Western Weeds. A Guide to the Weeds of Western Australia. 2nd ed. Plant Protection Society of Western Australia, Victoria Park, 2007. (4) M. Saqib et al. J. R. Soc. West. Aust. 90:175, 2007.

Crotalaria spectabilis Roth. (Fabaceae), commonly known as showy rattlebox, is an herbaceous legume mainly used as a green manure crop to improve soil properties and as a source of durable fiber. However, the plant is toxic to mammals and birds because of the presence of pyrrolidizine alkaloids. A native of India and the Malay Peninsula, the species has been introduced into other areas such as the United States and Pacific Islands where the plant is an invader of cultivated lands. Fasciated rattlebox plants were sighted in fields in New Delhi in February 2010, with approximately 99% of the examined plants symptomatic. Symptoms included flattening of stems in a descending gradient of severity from the apex to the base of each affected branch. Shoots showed longitudinal undulations bearing highly reduced leaves and uneven distribution of flowers and fruits. To identify the causal agent, 10 symptomatic plants and 8 asymptomatic plants (latter sampled from a field approximately 1.5 km away) were collected for nucleic acid analysis. Total genomic DNA was extracted from flattened stems as well as the roots of symptomatic plants, and from the same tissues of asymptomatic plants, and subjected to nested-PCR using phytoplasma 16S ribosomal DNA universal primer pair P1/P7, followed by R16F2/R2 (4). A known aster yellows-infected Catharanthus roseus plant was used as a control sample. Results depicted a characteristic phytoplasma amplicon of 1.25 kb in all samples from symptomatic plants and the control plant. No amplification was observed from asymptomatic plants. To obtain a full-length sequence, a representative amplicon was purified with the QIAquick gel extraction kit (QIAGEN, Valencia, CA), cloned into pGEM-T Easy vector (Promega, Madison, WI), and sequenced. Comparison of the 1,243-bp sequence (Genbank Accession No. HM137557) using BLAST analysis of the NCBI database showed 99% homology with sequences of members of 16SrI group phytoplasmas, i.e., ‘Candidatus Phytoplasma asteris’ such as Japanese spurge yellows (AB551736.1), Mulberry yellow dwarf (GQ249410.1), and Bamboo witches'-broom (FJ853161.1) phytoplasmas. The profiles of in vitro restriction fragment length polymorphism (RFLP) analysis obtained by digestion of the nested-PCR products with HhaI, KpnI, and AluI were similar to those of in silico RFLP analyses and coincided with the pattern of the 16SrI-B subgroup. Phylogenetic analysis of phytoplasma 16S rDNA sequences based on the maximum likelihood method using MEGA Version 4.1 also placed the Crotalaria fasciation (CF) phytoplasma within the 16SrI-B cluster. In India, C. tetragona plants infected with 16SrI phytoplasma (FJ185141) causing witches'-broom symptoms (1) showed 98% similarity with the CF phytoplasma. However, the results support previous molecular investigations associating 16SrI phytoplasma with fasciation of herbaceous plants, including Lilium spp. (2) and Asparagus officinalis (3). To our knowledge, C. spectabilis represents a new host that can be fasciated as a result of phytoplasma infection. Because of the weedy nature of C. spectabilis, this host could facilitate spread of the phytoplasma. References: (1) P. Baiswar et al. Plant Pathol. 19:17, 2009. (2) A. Bertaccini et al. FEMS Microbiol. Lett. 249:79, 2005. (3) J. Franova and K. Petrzik. J. Phytopathol. 158:317, 2010.K. (4) D. E. Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996.

Prunus persica (L.) Bastch (family Rosaceae) is currently represented by 83 accessions at the Canadian Clonal Genebank. Approximately 3,200 ha are devoted to peach cultivation in Canada where Ontario Province accounts for 82% of the national production. The clonal peach accessions, also located in Ontario, are monitored routinely for symptoms of phytoplasma infection, including rosette-like symptoms (3) that are characterized by new shoots with very short internodes, loss of older shoot leaves leaving only bunches of young leaves on the tips of naked shoots, and flowers that rarely set fruit. From June to August 2009, peach accessions PRU0382 and PRU0445 showed typical peach rosette symptoms, while another 14 accessions exhibited either short internodes or no symptoms. Leaf midrib samples were collected from 16 peach accessions, including 17 symptomatic (from which 8 corresponded to accession PRU0382, 6 for PRU0445, 1 for PRU0335, 1 for PRU0179, and 1 for PRU0451) and 16 asymptomatic (from which 5 corresponded to a representative of each accession PRU0382, PRU0445, PRU0335, PRU0179, and PRU0451 and 11 to other peach accessions). Total DNA was extracted (DNeasy Plant Extraction Mini Kit, QIAGEN, Valencia, CA) from 100 mg of each sample and used as a template in a nested PCR with phytoplasma universal primers R16mF2/R1 (1) and fU5/rU3 (2). Nested PCR products of the expected size (~880 bp) were obtained from all symptomatic samples (14 of 14) of accessions PRU0382 (peach-almond cv. Kando from the Czech Republic) and PRU0445 (peach cv. HW271 from Canada) only. All other plants with or without symptoms yielded no PCR products. Amplicons were purified (Wizard PCR Clean-up, Promega, Madison, WI), cloned in pGEM-T Easy Vector (Promega), and sequenced (Robarts Institute, London, Canada). The resulting 16S rDNA sequences were identical; one of each was archived in GenBank as Accession No. GU223904. BLAST analysis determined that the P. persica phytoplasma sequence shared 99% identity with 16S rDNA sequences of ‘Candidatus Phytoplasma asteris’-related strains. This relationship was also supported by restriction fragment length polymorphism analysis (RFLP) of rDNA amplicons using AluI, RsaI, and MseI endonucleases that yielded fragment profiles indicative of phytoplasmas belonging to group 16SrI (Aster Yellows), subgroup B (16SrI-B). Among phytoplasma diseases, those attributed to group 16SrI strains are most numerous and affect the widest plant host range. They include peach rosette in the United States and Europe (3) as well as diseases of various horticultural crops in Canada, including grapevine (4). To our knowledge, this is the first report of a subgroup 16SrI-B phytoplasma affecting peach in Canada. Early detection of phytoplasmas by PCR in accessions with both European and Canadian origins underscores the importance of prompt identification of infected plants for subsequent thermotherapy treatment to maintain the health of the collection and prevent further disease spread. References: (1) D. E Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35:1441, 1996. (2) K. H. Lorenz et al. Phytopathology 85:771, 1995. (3) C. Marcone et al. Acta Hortic. 386:471, 1995. (4) C. Y. Olivier et al. Plant Dis. 93:669, 2009.

The citrus industries of North and South America are endangered by Huanglongbing (HLB), also known as citrus greening, a devastating disease associated with ‘Candidatus Liberibacter asiaticus’ and ‘Ca. L. americanus’, two species of fastidious phloem-limited bacteria spread by the Asian citrus psyllid (ACP), Diaphorina citri, Kuwayama. The first reports of HLB from the Americas were from Brazil in 2004 followed by Florida in 2005 (3). The ACP was found in Belize in 2005 (S. Williams, personal communication) and is now present throughout Central America. On the basis of the report that the HLB-associated bacteria can be easily detected in the ACP vector (4), an initial sampling of ACP from 67 locations was collected in February 2009 from trees in the Belize, Corozal, Orange Walk, Stann Creek, and Toledo Districts of Belize, and shipped in 95% ethanol to Riverside, CA for analysis. DNA was extracted from lots containing three to five psyllids from each of the 67 samples with Fast DNA kits (MP Biomedicals, Solon, OH) and analyzed by multiplex qPCR for ‘Ca. L. asiaticus’ and ‘Ca. L. americanus’ with a Stratagene MX3005P thermocycler with primers and Taqman probes to detect the 16sRNA gene of ‘Ca. L. asiaticus’ or ‘Ca. L. americanus’ and a psyllid gene, wingless, as an internal control target (4). Nine of the sixty-seven psyllid extractions were clearly positive for ‘Ca. L. asiaticus’ with cycle threshold values of 24 to 29. ‘Ca. L. americanus’ was not detected in any of the samples. From the districts previously sampled for ACP, leaves and fruit peduncles were collected from Citrus sinensis and C. aurantifolia plants showing HLB symptoms of asymmetrical leaf mottle and lopsided fruit with aborted seeds. DNA extracted from 10 of the 12 plant samples with a Qiagen Plant DNeasy kit (Qiagen Inc., Valencia, CA) was positive for ‘Ca. L. asiaticus’ with the qPCR procedure of Li et al (3). The presence of ‘Ca. L. asiaticus’ in the positive plant and ACP samples was corroborated by amplification, cloning, and sequencing of a 1,168-bp region of the 16S rRNA gene (2) with SpeedSTAR HS DNA polymerase (TaKaRa Bio Inc., Shiga, Japan). Consensus sequences obtained from three clones each from psyllids (Accession No. GQ502291) and plants (Accession No. GU061003) showed >99% identity to corresponding regions of ‘Ca. L. asiaticus’ in GenBank. The presence of ‘Ca. L. asiaticus’ was further indicated by amplification of a 227-bp fragment from the same 10 positive plant samples using primers for the ‘Ca. L. asiaticus’ preprotein translocase subunit SecE gene (nucleotides 31418 to 31644 of the genomic DNA) (1). Presence of trees with HLB symptoms and the detection of the associated ‘Ca. L. asiaticus’ confirm the disease in the Cayo, Corozal, Stann Creek, and Toledo districts in Belize. Analyses of psyllids from limited surveys conducted from 2006 to 2008 had not detected ‘Ca. L. asiaticus’ or ‘Ca. L. americanus’. Confirmation of HLB in Belize has significant implications to the citrus industries in Central America. References: (1) T. H. Hung et al. J. Phytopathol. 147:599, 1999. (2) S. Jagoueix et al. Mol. Cell. Probes 10:43, 1996. (3) W. Li et al. J. Microbiol. Methods 66:104, 2006. (4) K. L. Manjunath et al. Phytopathology 98:387, 2008.

Huanglongbing (HLB), considered to be the most serious insect-vectored bacterial disease of citrus, is transmitted in nature by the Asian citrus psyllid Diaphorina citri and the African citrus psyllid Trioza erytreae. D. citri was discovered in southern Florida in 1998 and the HLB disease in 2005. Both have become established throughout citrus-producing areas of Florida. Murraya species are widely grown in southern Florida as ornamental hedges and are readily colonized by D. citri vectors. Colonies of D. citri, isolates of ‘Candidatus Liberibacter asiaticus’ from Taiwan and Florida, and the Murraya species were established in the BSL-3 biosecurity facility at Fort Detrick. In controlled inoculation experiments, D. citri transmitted ‘Ca. L. asiaticus’ into M. paniculata (34/36 plants) and M. exotica (22/23 plants), but not into Bergera (Murraya) koenigii. Disease symptoms rarely developed in Murraya plants; however, positive infections were determined by conventional and real-time polymerase chain reaction (PCR). Back-inoculations of ‘Ca. L. asiaticus’ from M. paniculata to Madam Vinous sweet orange resulted in disease development in 25% of the inoculated plants. Considerable variability was observed in infection rates, titer, and persistence of ‘Ca. L. asiaticus’ in infected Murraya.

Pear decline (PD) is a serious disease of pear (Pyrus communis L.) caused by ‘Candidatus Phytoplasma pyri’, which belongs to the subgroup 16SrX-C of the apple proliferation (AP) group of phytoplasmas (3). Pear seedlings from the Agriculture and Agri-Food Canada (AAFC) pear breeding program, which have been selected for advanced test and grower trials, are routinely submitted to the Canadian Food Inspection Agency (CFIA) Sidney Laboratory (formerly, CFIA Centre for Plant Health, Saanichton, BC) for virus testing at the same time that propagation is initiated to produce trees for further evaluations. In early 2007, the CFIA reported that samples of two seedling selections submitted in 2005 tested positive for phytoplasmas by a nested PCR assay with phytoplasma universal primers P1/P7 (1), followed by phytoplasma universal primers fU5/rU3 (2) and real time PCR with universal phytoplasma primers developed by the CFIA-Sidney (personal communication). Phytoplasmas present in both selections were subsequently identified as ‘Ca. P. pyri' strains by nested PCR with the P1/P7 primers followed by PD/peach yellow leaf roll (PYLR)-specific primers fPD/rPDS (2,4). These were the first PD-positive results from many samples submitted over the years for testing. Following PD-positive diagnoses for the seedling trees, others propagated from these seedling trees were removed from the nursery. When tested by PD-specific nested PCR (P1/P7 then fPD/rPDS), one selection had 39 of 79 nursery trees (49%) that were PD positive, while the other selection had 27 of 96 trees (28%) testing as PD positive. PCR amplification of DNA isolated from leaves of six of the propagated trees, with primer pair fPD/rPDS, yielded an ~1,400-bp product that was sequenced. A consensus sequence of 1,313 bp (GenBank Accession No. GU565959) was subjected to a nucleotide BLAST search of the NCBI database and showed 100% nt identity with sequences of phytoplasmas PD1 (AJ542543) and PYLR (Y16394). Subsequently, the PD-positive results from leaf, dormant shoot, and root tissues from the original seedling trees were confirmed by PD-specific nested PCR. On the original seedling trees, visible symptoms typical of PD, especially premature leaf coloration, were observed in late summer 2008 and samples taken of green and red leaves were subjected to PD-specific PCR. Red leaves were PD-positive, while green leaves were mostly PD-negative. Pear leaves, dormant shoots, and roots collected from research and commercial orchards in southern Ontario in 2007 and 2008 were subjected to PD-specific nested PCR (P1/P7 then fPD/rPDS), AP-specific nested PCR (P1/P7 then fO1/rO1) (2), as well as the universal phytoplasma nested PCR (P1/P7 then fU5/rU3), resulting in the identification of PD-positive trees of several cultivars. The sequence of the 1,057-bp amplicon from accession PYR0190 (selection HW615), with AP-specific primers fO1/rO1, was deposited in GenBank (GU475131). Although there have been no previous reports of PD in Ontario, Canada, it would appear that PD has been present for some time based on the number and distribution (both geographic and cultivar) of positive samples. References: (1) S. Deng and C. Hiruki. J. Microbiol. Methods 14:53, 1991. (2) K.-H. Lorenz et al. Phytopathology 85:771, 1995. (3) E. Seemüller et al. J. Plant Pathol. 80:3, 1998. (4) C. D. Smart et al. Appl. Environ. Microbiol. 62:2988, 1996.

Carrot (Daucus carota) plants with symptoms resembling those of carrot psyllid (Trioza apicalis) damage (3,4) were observed in 14 commercial fields in southern Finland in August 2008; all cultivars grown were affected at approximately 5 to 35% symptomatic plants per field. T. apicalis, a pest of carrots in northern and central Europe, can cause up to 100% crop loss (3,4). Symptoms on affected plants included leaf curling, yellow and purple discoloration of leaves, stunted growth of shoots and roots, and proliferation of secondary roots (3,4). Given recent association of liberibacter with several annual crops affected by psyllids (1,2), an investigation on whether this bacterium is associated with symptoms of psyllid damage on carrots was conducted. Total DNA was extracted from petiole tissue of 20 symptomatic and 18 asymptomatic plants (cv. Maestro, Nanda, Nipomo, Nerac, and Fontana) sampled from 10 psyllid-infested fields in southern Finland, as well as 15 plants (cv. Primecut, Cheyenne, and Triple Play) grown from seed in an insect-free greenhouse, with the cetyltrimethylammoniumbromide (CTAB) method (2). DNA was also extracted from 10 carrot roots (cv. Nantura) of plants continuously exposed to field-collected carrot psyllid colonies in the laboratory. DNA samples were tested by PCR using primer pairs OA2/OI2c and CL514F/R to amplify a portion of 16S rDNA and rplJ/rplL ribosomal protein genes, respectively, of “Candidatus Liberibacter solanacearum” (1,2). A 1,168 bp 16S rDNA fragment was detected in DNA from 1 asymptomatic and 16 symptomatic plants and a 669 bp rplJ/rplL fragment was amplified from DNA from 19 symptomatic and 6 asymptomatic plants, indicating presence of liberibacter. DNA from all 10 root samples yielded similar amplicons with both primer pairs. DNA from all the greenhouse carrot plants yielded no amplicon. Amplicons from DNA from three petioles and three roots with each primer pair were cloned (pCR2.1-TOPO; Invitrogen, Carlsbad, CA) and three clones of each of the 12 amplicons were sequenced (MCLAB, San Francisco, CA). BLAST analysis of the 16S rDNA consensus sequences from petiole and root tissues (GenBank Accession Nos. GU373049 and GU373048, respectively) showed 99.9% identity to those of “Ca. L. solanacearum” amplified from Capsicum annuum (FJ957896) and Solanum lycopersicum (FJ957897) from Mexico, and “Ca. L. psyllaurous” from potato psyllids (EU812559). The rplJ/rplL consensus sequences from petioles and roots (GenBank Accession Nos. GU373051 and GU373050, respectively) were 97.9% identical to the analogous rplJ/rplL “Ca. L. solanacearum” ribosomal protein gene sequence from solanaceous crops in New Zealand (EU834131) and to “Ca. Liberibacter” sp. sequence from zebra chip-affected potatoes in California (FJ498803). To our knowledge, this is the first report of “Ca. L. solanacearum” associated with a nonsolanaceous species and the first report of this pathogen outside of North and Central America and New Zealand (1,2). References: (1) L. W. Liefting et al. Plant Dis. 93:208, 2009. (2) J. E. Munyaneza et al. Plant Dis. 93:552, 2009. (3) G. Nehlin et al. J. Chem. Ecol. 20:771, 1994. (4) A. Nissinen et al. Entomol. Exp. Appl. 125:277, 2007.

In August 2008, 30% of tomato (Solanum lycopersicum) plants in plots in Lubbock County, Texas showed yellowing, lateral stem dieback, upward leaf curling, enlargement of stems, adventitious roots, and swollen nodes. Yellowing in leaves was similar to that seen with zebra chip disease (ZC) of potato that was confirmed in a potato field 112 km away in July 2008 and was associated with a ‘Candidatus Liberibacter’ species (1), similar to findings earlier in 2008 in New Zealand and California (2,3). Tissue from four symptomatic plants of cv. Spitfire and two of cv. Celebrity were collected and DNA was extracted from midribs and petioles with a FastDNA Spin Kit (Qbiogene, Inc., Carlsbad, CA,). PCR amplification was done with 16S rRNA gene primers OA2 and OI2c, which are specific for “Ca. Liberibacter solanacearum” from potato and tomato and amplify a 1.1-kb fragment of the 16S rRNA gene of this new species (1,3). Amplicons of 1.1 kb were obtained from all samples and these were sequenced in both orientations (McLab, San Francisco, CA). Sequences of the 16S rRNA gene were identical for both Spitfire and Celebrity and were submitted to the NCBI as GenBank Accession Nos. FJ939136 and FJ939137, respectively. On the basis of a BLAST search, sequence alignments revealed 99.9% identity with a new species of ‘Ca. Liberibacter’ from potato (EU884128 and EU884129) in Texas (1); 99.7% identity with the new species “Ca. Liberibacter solanacearum” described from potato and tomato (3) in New Zealand (EU849020 and EU834130, respectively) and from the potato psyllid Bactericera cockerelli in California (2) (EU812559, EU812556); 97% identity with ‘Ca L. asiaticus’ from citrus in Malaysia (EU224393) and 94% identity with both ‘Ca. L. africanus’ and ‘Ca. L. americanus’ from citrus (EU921620 and AY742824, respectively). A neighbor-joining cladogram constructed using the 16S rRNA gene fragments delineated four clusters corresponding to each species, and these sequences clustered with “Ca. L. solanacearum”. A second PCR analysis was conducted with the CL514F/CL514R primer pair, which amplifies a sequence from the rplJ and rplL ribosomal protein genes of “Ca. L. solanacearum”. The resulting 669-bp products were 100% identical to a sequence reported from tomato in Mexico (FJ498807). This sequence was submitted to NCBI (GU169328). ZC, a disease causing losses to the potato industry, is associated with a ‘Candidatus Liberibacter’ species (1–3) and was reported in Central America and Mexico in the 1990s, in Texas in 2000, and more recently in other states in the United States (4). In 2008, a “Ca. Liberibacter solanacearum” was detected on Capsicum annuum, S. betaceum, and Physalis peruviana in New Zealand (3). Several studies have shown that the potato psyllid, B. cockerelli, is a potential vector for this pathogen (2,4). To our knowledge, this is the first report of “Ca. Liberibacter solanacearum” in field tomatoes showing ZC-like foliar disease symptoms in the United States. References: (1). J. A. Abad et al. Plant Dis. 93:108, 2009 (2) A. K. Hansen et al. Appl. Environ. Microbiol. 74:5862, 2008. (3) L. W. Liefting et al. Plant Dis. 93:208, 2009. (4) G. A. Secor et al. Plant Dis. 93:574, 2009.