RESUMO
Giant cardon (Pachycereus pringlei ((S.Watson) Britton & Rose) is the most common cactus in northwestern Mexico and is endemic to the Baja California Peninsula and Sonora Desert. A large part of the peninsula (El Vizcaino Biosphere Reserve and Gulf of California) now consists of protected areas and is classified as a World Heritage site by UNESCO ( http://whc.unesco.org/en/list/1182 ). Cardon cactus is an important ecological resource for indigenous people and is used as feed for range cattle. Since 2000, in the central and southern part of the State of Baja California Sur, an apical stem rot has spread to ~17% of the natural cardon population around San Pedro (23°29'N, 110°12'W), La Paz (24°08'N, 110°18'W), and El Comitán (24°05'N, 110°21'W). Affected cacti display necrosis of apical branches, dry rot, cracks in the stem and branches, bronzing of mature spines surrounding the affected area, and reddish brown gummy exudate. Thirty samples from the edges of symptomatic lesions were surface disinfected for 2 min in 0.8% (wt/vol) NaOCl and ethanol (70%), rinsed in sterile, distilled water, and grown on potato dextrose agar at 27°C. A cottony, brownish fungus was consistently isolated from affected tissues. Koch's postulates were performed in pots of 10 cm in diameter with 5-year-old cacti inoculated (9-day-old mycelia) and incubated (15 days) at room temperature (26°C). The rough, dry, brownish, circular lesions that appeared were the same as those observed in the field. Healthy cacti inoculated with potato dextrose agar plugs were symptomless. The fungus was always reisolated from infected cacti and morphological examinations (2) were performed: one-septate, olive-green, smooth, ellipsoidal conidium and two-celled ascospores (15 to 20 × 5 to 7 µm) were present. Also present were conidial masses from monomorphic, penicillate conidiophores in sporodochia. Cottony and white-to-light yellow PDA colonies were observed. Genomic DNA was extracted from lyophilized hyphae using the method described by O'Donnell (1) or with a DNeasy Plant Mini Kit (Qiagen, Hilden, Germany). The internal transcribed spacer (ITS) regions 1 and 2 of the 5.8, 18, and 28S ribosomal RNA genes were amplified with the primer pairs ITS1 and ITS4 (3). The expected amplicon of 571 bp was sequenced and compared with fungal sequences available from the GenBank-EMBL database using the BlastN and CLUSTAL programs (MegAlign, DNASTAR, Madison, WI). The closest nucleotide similarity had 99% identity with a Bionectria sp. (GenBank Accession No. HM849058.1). To our knowledge, on the basis of morphological characteristics, DNA comparisons, and pathogenicity tests, this is the first report of a Bionectria sp. causing an apical stem rot disease in cardon cacti in Mexico. Since there are no control measures in Mexico there is a permanent risk that the disease will spread to healthy areas. References: (1) K. O'Donell et al. Mycologia 92:919, 2000. (2) H. J. Schroers. Stud. Mycol. 46:1, 2001. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.
RESUMO
Sour rot caused by Geotrichum citri-aurantii (Ferraris) R. Cif. & F. Cif. (synonym G. candidum Link) is a disease that causes postharvest losses of lemon (Citrus limon Burm, f.), mandarin (C. reticulata Blanco), and orange (C. sinensis (L.) Osbeck) (2-4) worldwide, but it has not been described on key lime (C. aurantifolia (Chistm.) Swingle) from the State of Colima, Mexico. During the agricultural cycle from 2005 to 2007, 300 fruits of key lime were analyzed. Symptoms observed on approximately 40% of the fruits were wounds with a sour, fermented smell with 30% of the softened area covered with white mycelium. A Geotrichum sp. was isolated on potato dextrose agar (PDA). On the basis of morphological criteria (1) and sequencing the internal transcribed spacer (ITS1-5.8s-ITS2) region of rDNA (GenBank Accession No. EU131181), the fungus was identified as G. citri-aurantii. A sample of the fungus was deposited in the Biology Collection of Yeast and Fungi (Reg. No. CLT20) of Centro de Investigaciones Biológicas del Noroeste, Mexico. Key limes were inoculated with G. citri-aurantii by placing three drops (20 µl each) of a sterile water suspension of 106 arthroconidia/ml in three punctured wounds of 3-mm diameter produced with a sterile scalpel on the fruit surface. Ten plastic boxes with five fruit each were stored for 2 weeks at 20°C and 85% relative humidity. Sour rot symptoms on key lime inoculated with G. citri-aurantii were identical to fruit in the field. The control fruit inoculated with sterile water did not develop symptoms. The fungus was reisolated, confirming Koch's postulates. The test was repeated three times to confirm our diagnosis. To our knowledge, this is the first report of G. citri-aurantii causing sour rot on key lime in Colima, Mexico. References: (1) S. Gente et al. J. Ind. Microbiol. Biotechnol. 33:1019, 2006. (2) P. Plaza et al. J. Hortic. Sci. Biotechnol. 79:935, 2004. (3) J. L. Smilanick et al. Post. Biol. Tech. 47:226, 2008. (4) V. H. Tournas and E. Katsoudas, J. Food. Microbiol. 105:11, 2005.
RESUMO
Since 2000, a phytoplasma-like disease (locally known as "permanent yellowing") was observed on tomatoes (Lycopersicon esculentum Mill.) grown in the Valle de San Quintín in northern Baja California Peninsula. Affected plants showed general chlorosis, severe stunting, upwardly rolled leaves, bronzing of mature leaves, purple discoloration of veins, "little leaf", abnormal floral structures, and excessive branching of axillary shoots. Total DNA extracted from symptomatic and asymptomatic plants was used in nested (n)-PCR assays driven by phytoplasma-universal primer pair P1/P7 (3), followed by primer pair R16F2n/R16R2 (1) targeting the 16S ribosomal RNA gene of the putative phytoplasma. PCR conditions (direct and nested) were conducted as previously described (l,3). Restriction fragment length polymorphism (RFLP) patterns of nPCR-amplified products (≈ 1.25-kbp 16S rDNA fragments) digested with enzymes AluI, MseI, HhaI, and HpaII showed that 85% (17 of 20) of PCR-positive tomato samples had restriction patterns typical of phytoplasmas belonging to the aster yellows group, subgroup B (16SrI-B) "Candidatus Phytoplasma asteris" (2). Only 10% (2 of 20) of the samples were associated with a phytoplasma related to the 16SrXIII-A Mexican periwinkle virescence group (formerly group 16SrI, subgroup I). None of the symptomless plants tested positive. Subsequently, these results were confirmed by nPCR using 16SrI specific primer pair P1/Aint (4) and specific primers rp(I-B)F1/rp(I-B)R1 that amplify the ribosomal protein (rp) gene operon of aster yellows phytoplasma subgroup B (16SrI-B[rp-B]) (1). The presence of the phytoplasmas in symptomatic plants was confirmed by scanning electron microscopy. Characteristic yellow symptoms could be experimentally reproduced by graft inoculation of tomato seedlings (cv. Maya) with tissue of field-infected plants. Symptoms similar to those of field-grown diseased plants were observed consistently in most of the plants, and when graft transmitted from tomato to periwinkle (Catharantus roseus (L.) G. Don), symptoms of virescencent, small flowers were observed. In contrast, no symptoms were observed on plants grafted with tissues from healthy plants. In Baja California, it appears that at least two distinct phytoplasmas are involved in the disease complex. To our knowledge, this is the first molecular evidence of the presence of a phytoplasma associated with yellows-type diseases in the major tomato cultivation areas of the peninsula. References: (1) I.-M. Lee et al. Phytopathology 93:1368, 2003. (2) I.-M. Lee et al. Int. J. Syst. Evol. Microbiol. 54:1037, 2004. (3) B. Schneider et al. Page 369 in: Molecular and Diagnostic Procedures in Mycoplasmology. Academic Press, San Diego, CA, 1995. (4) C. D. Smart et al. Appl. Environ. Microbiol. 62:2988, 1996.
RESUMO
In 2005, serological screening by ELISA of 24 tomato (Solanum lycopersicon Mill.) plants with virus-like foliar symptoms (locally known as "marchitez manchada" [spotted wilt] disease) was done for a variety of RNA viruses: Tomato spotted wilt virus (TSWV; family Bunyaviridae, genus Tospovirus) was specifically detected. The symptomatic plants testing positive were from the most important tomato areas in San Quintin, in the north of Baja California. Symptoms characteristic of TSWV (4), including chlorosis, malformation of apical leaves, stunting, and ringspot lesions, were observed in this region and throughout the peninsula. In 2006, 42 symptomatic tomato plants from La Paz, in the south of Baja California, were analyzed for TSWV by double-antibody sandwich (DAS)-ELISA with a commercially available kit (TSWV ImmunoStrip Kit; Agdia Inc., Elkhart, IN). Total nucleic acids of the TSWV ELISA-positive samples (16 of 42 = 38%) were extracted and preserved on FTA cards (Whatman, Brentford, U.K.) and processed according to the manufacturer's protocol. The positive TSWV samples were verified by reverse transcription (RT)-PCR with primers specific to the TSWV nucleocapsid protein gene, 5'-ATGTCTAAGGTTAAGCTC-3' and 5'-TTAAGCAAGTTCTGTGAG-3' (2). Amplicons of the expected size (approximately 800 bp) were obtained from all 16 positive samples but not in the ELISA-negative samples. The spotted wilt disease was mechanically transmitted to tomato (cv. Rutgers) and Nicotiana glauca seedlings. Symptoms on leaves consisting of chlorotic ring patterns and necrotic lesions were observed in tomato, and slightly concentric chlorotic lesions were observed in N. glauca. All symptomatic plants from San Quintin and La Paz were positive for TSWV in the DAS-ELISA and RT-PCR tests and none were positive for the tobamoviruses, Tomato mosaic virus (ToMV) and Tobacco mosaic virus (TMV). TSWV was not detected in symptomless tomato plants used as negative controls. TSWV was detected in Mexico in tomatillo (Physalis ixocarpa), tobacco (Nicotiana tabacum), jimsonweed (Datura stramonium) (3), and recently, in tomato and pepper in the Central Plateau of Mexico (1). Although spotted wilt disease has been previously observed in San Quintin tomato-producing areas, to our knowledge, this is the first confirmation of TSWV in the Baja Peninsula. The role of weed hosts as a natural reservoir and the role of species of thrips in the epidemiology of the disease are currently unknown, although the incidence of the virus in these regions has risen to destructive levels in tomato. References: (1) R. De La Torre-Almaráz et al. Agrociencia 36:211, 2002. (2). R. K. Jain et al. Plant Dis. 82:900, 1998. (3) M. E. Llamas-Llamas et al. Plant Pathol. 47:341, 1998. (4) G. Marchoux et al. Plant Pathol. 40:347, 1991.
RESUMO
During the 2005 tomato-growing (Lycopersicon esculentum Mill.) season, an apparent bacterial disease with cankers on the stems and bird's eye lesions on the fruit appeared in commercial fields and greenhouses in the San Quintin and San Simon areas (a 60-mile long coastal plain) near the central region of the Baja California Peninsula of Mexico. The disease was found in midseason, especially when plants were flowering, and the mature and ripe stage. Incidence ranged from 4 to 46%, which represented an important loss in field and greenhouse production. Symptomatic plants showed reddish brown cavities in the stem, discoloration, and water soaking of vascular tissue. Diseased tissues were washed with phosphate buffer and placed on semiselective Clavibacter medium (SCM) (1), and a gram-positive, nonmotile, nonspore-forming, aerobic, curved rod bacterium was consistently isolated and morphologically characterized. Twenty-eight isolates were identified as Clavibacter michiganensis subsp. michiganensis by polymerase chain reaction (PCR) technology with primers CMM5/CMM6 to amplify a fragment of approximately 6.2 kb (2). The isolates were also identified by REP-PCR (repetitive extragenic palindromic PCR) genomic fingerprinting techniques (3) with REP and BOX primer sets (4). Pathogenicity tests consisting of three replicates of 4-week-old tomato seedlings (cv. Tequila) were performed by spraying (twice, 2 days apart) inocula at 108 CFU/ml. Control seedlings were sprayed with sterile water. Inoculated plants previously covered in polyethylene bags were incubated in a growth chamber at 25°C for 48 h. Within 3 weeks, symptoms of reddish-brown cavities, water-soaked lesions, and asymmetrical wilting appeared on inoculated plants and were similar to those symptoms observed in the field. No symptoms were observed on control plants. Confirmation of the causal agent was done by culturing the bacteria on SCM and PCR analysis. Occurrence of the disease in San Quintin Valley is relevant because the disease is one of the five most serious tomato diseases in the peninsula. Moreover, the potential spread of the pathogen by tomato seedlings represents a permanent risk to other pathogen-free areas in the peninsula. Although bacterial canker has been observed in Baja California (Punta Colonet, Vicente Guerrero, San Quintin, and San Simon), to our knowledge, this is the first confirmation of C. michiganensis subsp. michiganensis in Baja, Mexico. References: (1). C. Alarcon et al. Phytopathology 88:306, 1998. (2) J. Dreier et al. Phytopathology 85:462, 1995. (3) F. J. Louws et al. Phytopathology 88:862, 1998. (4) J. Versalovic et al. Methods Mol. Cell. Biol. 5:25, 1994.
RESUMO
Since 2001, geminivirus-like disease symptoms have been observed in tomato plants on the Baja California Peninsula of Mexico. These diseases have been associated with large populations of Bemisia tabaci (Genn.) in commercial fields and have caused dramatic decreases in expected yields. Leaf samples from tomato plants displaying symptoms of stunting and severe upward leaf curling were collected in March 2002 in fields located near the city of La Paz, Baja California Sur (BCS). Total DNA was extracted and tested for the presence of geminiviral DNA using polymerase chain reaction (PCR) with begomovirus-specific degenerate primer pairs PALIv1978/PARIc494 and PALIc1978/PARIv494 (4). PCR products of the expected size (~1.16 and ~1.45 kb) were obtained, cloned into pGEM-T Easy (Promega, Madison, WI), and sequenced. Restriction fragment length polymorphism analysis of the PCR fragments was performed using EcoRI, HindIII, PstI, and XbaI. Restriction fragment patterns were the same for all amplicons and no evidence of mixed infection was obtained. In addition, experimental transmission by whiteflies and inoculations by biolistics consistently induced severe leaf epinasty and stunted growth on tomato seedlings. The complete (2,606 nt) DNA-A sequence of the infecting virus was determined (GenBank Accession No. AY339618) and compared with viral sequences available at GenBank-EMBL databases using BLASTN and the CLUSTAL program (MegAlign, DNASTAR, Madison, WI). The highest nucleotide identity was obtained with the recently described Tomato chino Baja California virus, ToChBCV (90.2%, GenBank Accession No. AY339619), isolated from tomato plantings in El Carrizal, BCS, 100 km from La Paz (3). The second and third best scores were obtained with Tomato severe leaf curl virus from Nicaragua (ToSLCV-NI, 79.6%, GenBank Accession No. AJ508784) and Guatemala (ToSLCV-GT94, 73.8%, GenBank Accession No. AF130415), respectively. Overall, sequence similarity with other New World begomoviruses was rather low (less than 70% identity). Careful analysis of differences between the La Paz isolate and its closest relative, ToChBCV from El Carrizal, revealed that they display different Ori-associated iterons (i.e., replication (Rep)-binding sites) having GGAGTA and GGGTCY core sequences, respectively (1). Moreover, sequence comparisons of the Rep-binding domain (aa 1-120) showed that these domains are only 71% identical. Current taxonomic criteria for begomoviruses establishes that a virus DNA-A sequence identity below 89% with its closest relative is indicative of a separate species (2). Since the La Paz and El Carrizal isolates share 90.2% nt identity, they should be considered strains of a same virus species, recently renamed Tomato chino La Paz virus, ToChLPV (2). Nevertheless, the remarkable differences in their putative replication specificity determinants suggest that ToChLPV and ToChLPV-[BCS] could be incompatible in replication, an interesting issue that should be experimentally addressed. References: (1) G. R. Arguello-Astorga et al. Virology 203:90, 1994. (2) C. Fauquet and J. Stanley. Arch. Virol. 150:2151, 2005. (3) R. J. Holguín-Peña et al. Plant Dis. 89:341, 2005. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.
RESUMO
Vascular wilting diseases have become one of the most serious diseases of tomato (Lycopersicon esculentum) throughout the Baja California Peninsula. Since the winter of 2004, a disease with symptoms characteristic of those caused by a Fusarium species has been observed in commercial fields near La Paz and Todos Santos in the state of Baja California Sur (BCS). Symptoms include typical one-sided wilting and dark brown vascular discoloration. Upper stem tissues and wilted seedlings were disinfested by immersion in a 1.0% aqueous solution of sodium hypochlorite for 2 min, rinsed in sterile water, and placed on Komada's medium (pH 6.8) at 22 ± 3°C. After 72 h, hyphal growth was recovered and subcultured on carnation leaf agar and potato dextrose agar and incubated at 25°C in 12-h light/dark cycles. Identification was based on colony morphology, conidial characteristics, and molecular techniques. White cottony mycelium, reddish coloration of the medium, ovoid two-celled macroconidia, and large macroconidia, all characteristic of F. oxysporum, were observed (2). Polymerase chain reaction and restriction fragment length polymorphisms with restriction enzymes EcoRI, RsaI, and HaeIII were used to characterize 24 isolates (sampled during January 2005) from La Paz (Fol-LaP) as formae speciales lycopersici and assigned to vegetative compatibility group 0030 (1). Confirmation of pathogenicity and race determination for the Fol-LaP isolates were as described previously (3). Mexican isolates of races 2 and 3 (one each) were included as positive controls. Conidial suspensions of 7 × 105 CFU/ml were used to inoculate differential tomato cvs. Bonny Best (Millington Co., universally susceptible), Tequila F1 (Vilmorin, race 1 resistant), Rio Grande (Harris Moran, race 1 and 2 resistant), and Sebring (Rogers, race 1, 2, and 3 resistant). Plants at the first true-leaf stage were inoculated by dipping their roots in the conidial suspension. Inoculated seedlings were transplanted into pots containing a sterile 5:1:1 mixture of sand/vermiculite/soil (v/v/v) and maintained in the greenhouse at 25 to 28°C under natural daylight. An equal number of plants of each cultivar dipped in water were used as controls. The experimental design was a completely randomized type with six replications (pots) containing four seedlings per pot. The test was done twice. The most susceptible plants inoculated by root-dipping developed typical symptoms of wilt, slight vein clearing on outer leaflets, stunting, dark brown vascular discoloration, and death. F. oxysporum was recovered from all symptomatic plants, whereas noninoculated tomato seedlings showed no symptoms. According to differential infection and symptomatology observed on infected cultivars, 62.5% of the isolated strains were identified as race 2, 25% as race 3, and 12.5% as an undetermined race isolated from Sebring. The presence of race 3 in BCS has important epidemiological implications since it has been reported on tomato in Sinaloa (4). The potential spread of the pathogen on introduced transplants represents a risk to tomato crops on the peninsula. To our knowledge, this is the first report of F. oxysporum f. sp. lycopersici race 3 in the state of BCS, Mexico. References: (1) G. Cai et al. Phytopathology 93:1014, 2003. (2) P. E. Nelson et al. Fusarium species. Pennsylvania State University Press, University Park, 1983. (3) B. A. Summerell et al. Plant Dis. 87:117, 2003. (4) J. G. Valenzuela-Ureta et al. Plant Dis. 80:105, 1996.
RESUMO
More than 10,000 ha of tomatoes are grown in the field and greenhouses on the Baja California Peninsula of Mexico. Information about the etiology of geminivirus-like diseases affecting tomato crops in all horticultural regions in the area has been difficult to obtain and assess. From 2001 through 2003, stunting, foliar discoloration, reduced leaf size, and leaf crumpling symptoms were observed and analyzed in one large area of tomato plantings in El Carrizal (near the city of La Paz in Baja California Sur). This leaf curl disease resembled that caused by Chino del tomate virus and has been observed at levels of incidence ranging from 60 to 90%. DNA isolated from symptomatic plants was analyzed using DNA hybridizaton and polymerase chain reaction (PCR) amplification of the 5' regions of the replication and coat protein genes, including the intergenic region (3). Comparisons of the nucleotide sequence (GenBank Accession No. AY339619) with corresponding sequences in GenBank resulted in 84.2% identity with Tomato mild mottle virus and 61.7% with Tomato severe leaf curl virus; both isolates originate from Central America. The relatively low nucleotide sequence identities from its closest relatives suggested that the virus may be a new begomovirus species of unambiguous American ancestry. In a phylogenetic analysis using PAUP 4.0 software, the Baja California isolate clustered in a separate group from other Mexican sequences. Moreover, the iteron (iterative sequences motifs associated in virus replication) arrangements (1) are unique among known New World begomoviruses, but identical to analogous elements from a tobacco-infecting begomovirus from China. On the other hand, it is well known that there are interactions between geminiviruses in mixed infections in some horticultural areas of Mexico (2). To determine the identity of the putative geminivirus involved in the disease, we used selected restriction enzyme (EcoRI, HindIII and XbaI) analysis and PCR with specific primers. No evidence of mixed infections with other geminiviruses was obtained. DNA fragments of the expected size (1.1 kb) showed different digestion patterns compared with other well-characterized geminiviruses isolated from Mexico such as Chino del tomate virus, Pepper huasteco yellow vein virus, Tomato leaf curl Sinaloa virus, and Pepper golden mosaic virus. Epidemiological, experimental, and natural host range studies indicated that the Baja California isolate has a relatively narrow host range infecting tomatoes, peppers (Capsicum annuum L.), and Peruvian apple (Nicandra physalodes L.). Reproduction of characteristic leaf curling symptoms in tomato seedlings infected with viruliferous whiteflies (Bemisia tabaci Genn.) and inoculated biolistically using infectious DNA (0.5 µg/ml) as inoculum were obtained. Koch's postulates were completed using PCR and DNA hybridization to confirm virus identity. These results confirm that the Baja California isolate is different from other begomoviruses isolated from Mexico. The virus is tentatively named Tomato chino Baja California virus (ToChBCV), genus Begomovirus, family Geminiviridae. References: (1) G. R. Arguello-Astorga et al. Arch. Virol. 146:1465, 2001. (2) J. Mendez-Lozano et al. Phytopathology 93:270, 2003. (3) M. R. Rojas et al. Plant Dis. 77:340, 1993.
RESUMO
San Quintin Valley, a 60-mile-long coastal plain (30°30'N, 116°W) in the Baja California Peninsula, is one of the major fresh tomato (Lycopersicon esculentum Mill.) production areas in Mexico with more than 8,000 ha. During the last 10 years, the valley's tomato production has declined because of gray mold and stem canker diseases. Flower rot, reddish brown margins on the leaves and stems, and fruit with a gray mold were observed on field-grown tomato plants (Roma type cv. Tequila) in the autumn of 2003. Severity ranging from 55 to 60% was observed at harvest. Infected tissues were sampled and disinfested by immersion in 1% NaOCl for 1 min, rinsed in sterile water, and placed on malt extract agar at 22°C. Fungal conidia were then transferred to 2% potato dextrose agar (PDA). The resulting fungal colonies were definitively identified as Botrytis cinerea Pers.:Fr. The colonies of B. cinerea were first hyaline and white and became dark gray after 96 h. Mycelia were septate with dark branched conidiophores. Conidia were unicellular, ellipsoid, and ranged from 5 to 8 × 8 to 14 µm. Profuse black sclerotia developed in 7-day-old cultures. Infection site analyses in diseased flowers at different stages during the bloom were done with scanning electron microscopy. Fungal hyphae were located predominantly on the receptacle areas, whereas conidia were located in the ovaries as described previously (3). The identity of B. cinerea was confirmed by a restriction digest with ApoI of the 413-kb polymerase chain reaction amplification product obtained with BA2f/BA1r primers (1) and random amplified polymorphic DNA banding patterns (2). Pathogenicity tests were done by spray inoculation of 1-ml aqueous conidial suspension (106 CFU/ml) on 20 healthy plants during the blossom stage. An equal number of plants sprayed with sterile water was used as the control. Plants were incubated at 20 ± 2°C for 5 days. The fungus was reisolated from diseased flowers and peduncles after surface disinfestation (2.5% NaOCl) and plating on PDA. No symptoms were observed in the noninoculated controls. To our knowledge, this is the first report of B. cinerea causing gray mold disease on tomato in Baja California. References: (1) K. Nielsen et al. Plant Dis. 86:682, 2002. (2) S. Rigotti et al. FEMS Microbiol. Lett. 209:169, 2002. (3) O. Viret et al. Phytopathology 94:850, 2004.
RESUMO
In the state of Baja California Sur, tomatoes (Lycopersicon esculentum Mill.) are cultivated on approximately 1,000 ha. Occurrence of viral diseases is currently causing low yields and severe losses. Virus-like symptoms (severe leaf curling, stunting, reduced leaf size, and mosaic patterns) were observed on 99% of tomato plants in 2002 in La Paz, Baja California Sur. Whiteflies (Bemisia tabaci Gennadius) were present in affected fields and appeared to be associated with the disease. The virus was experimentally transmitted from infected plants to tomato and peppers seedlings by whiteflies and as infectious DNA (replicative form) by mechanical and biolistic inoculation. Symptoms similar to those found in the field were observed in experimental transmission assays. DNA from inoculated plants was extracted and analyzed by DNA hybridization and polymerase chain reaction (PCR) using degenerate (1) and specific (2) primers. The PCR products (1.1 kb) obtained from the common region (GenBank Accession No. AY368336) suggested the presence of a bipartite geminivirus. The nucleotide sequence of the PCR products showed a 98% identity to Pepper golden mosaic virus-Tamaulipas strain (PepGMV-Tam) in the intergenic region (IR). Similar identities (97%) were obtained by using the predicted amino acid sequences of the amino termini of the coat proteins. Identities in the replication proteins (92%) and IR iterative sequence analyses show that the PepGMV-La Paz isolate is a closely related strain of PepGMV-Tam. To our knowledge, this is the first report of PepGMV affecting tomato crops in Baja California Sur, Mexico. References: (1) M. R. Rojas et al. Plant Dis. 77:340. 1993. (2) I. Torres-Pacheco et al. Phytopathology 86:1186, 1996.
RESUMO
Since November 2001, geminivirus-like symptoms (stunting, reduced leaf size, and leaf curling "chino") have been observed in tomato (Lycopersicon esculentum Mill.) plantings in Baja California Sur, Mexico. Samples of symptomatic plants were collected from commercial fields and analyzed by traditional and molecular methods for the presence of geminiviruses. Inocula prepared from infected plants were experimentally transmitted to tomato seedlings and Datura stramonium by mechanical inoculation and whitefly transmission. Leaf curling and interveinal chlorosis symptoms similar to those found in the field were observed in inoculated tomato and D. stramonium. DNA from infected plants was extracted and analyzed by polymerase chain reaction (PCR) and electrophoresis using degenerate primers PALIv1978/PARIc494 (1). PCR fragments of the expected size (1.1 kb) for the common region (CR) were obtained from 28 of 64 plants, cloned and sequenced (GenBank Accession No. AY336088). Comparisons of CR sequences with the NCBI database by using BLAST and MegAlign (DNASTAR, London) indicated that the Baja Californian isolates were New World bipartite begomoviruses sharing the highest nucleotide sequence identity (93%) with a partially characterized geminivirus (Tomato severe leaf curl virus (ToSLCV); GenBank Accession No. AF130415) from Guatemala. References: (1) M. R. Rojas et al. Plant Dis. 77:340, 1993.