First report of Tomato blistering mosaic virus infecting tomato in Argentina

Tomato (Solanum lycopersicum) ranks as the most important crop among greenhouse-planted crops in terms of cultivated areas (17,800 ha) and production in Argentina. In September 2014, farmers reported that tomato plants of cv. Elpida (Enza Zaden) showed mosaic and blistering on leaves in La Plata (Buenos Aires green-belt). The diseased plants occurred together in the same line, showing a typical pattern of mechanically transmitted pathogens. Although incidence did not exceed 1.5%, it was distributed in several distant locations within the district, posting a serious threat to the tomato production. Five samples were collected from symptomatic plants and tested for Tospovirus, Begomovirus, and Cucumber mosaic virus by reverse transcription polymerase chain reaction (RT-PCR) (Dewey et al. 1996), PCR (Rojas et al. 1993), and enzyme-linked immunosorbent assay (ELISA), respectively. All results were negative. The samples were then examined under transmission electron microscopy. Isometric virus-like particles of 25 to 30 nm in diameter were seen in leaf-dip preparations, and isometric virus-like particles aggregated in the cytoplasm of mesophyll cells and alterations of chloroplast membrane in association to virus-like particles were observed in ultrathin sections suggesting a Tymovirus. To identify this virus, leaf and stem samples were dot blotted on a nitrocellulose membrane and incubated with Tomato blistering mosaic virus (ToBMV) antiserum, kindly provided by Dr. Alice K. Inoue-Nagata (Embrapa-Horticulture, Brazil). The samples reacted to the ToBMV antiserum, indicating the presence of ToBMV or a ToBMV-related virus. Sap of the diseased samples was used to inoculate tomato cv. Elpida and several indicator plants (Datura stramonium, Nicotiana benthamiana, Nicotiana tabacum cv. TNN, Capsicum annuum cv. Almuden, and Chenopodium quinoa). The inoculated tomato plants showed foliar chlorosis, mosaic, necrosis, and blistering similar to those observed in the greenhouses, and the indicator plants reproduced the symptoms reported by de Oliveira et al. (2013). Furthermore, two samples were subjected to RT-PCR using primers specifically designed to amplify the complete capsid protein (CP) from ToBMV: TymoF3RaceFor, 5′-TCCAATCCATGCCTTTTGAT-3′; and ToBMV3EndNdeIRev, 5′-TTCATATGGTTTCCGATACCCTCGG-3′. DNA fragments of expected size (1000 bp) were amplified, cloned in pGEM-T easy (Promega), and sequenced. Sequence analysis showed the nucleotide sequences of the two isolates were identical, suggesting that they are the same variant (Accession No. KT235894). This isolate shares 92% identity with tomato isolate SC50 (Nicolini et al. 2015) and tobacco isolate BR001 (Melo et al. 2014), both from Brazil. These results indicate that the tomato disease in Buenos Aires green-belt is caused by ToBMV. To our knowledge, this is the first report of ToBMV infecting tomato in Argentina. This finding has an important epidemiological impact because ToBMV represents a new problem to tomato crops in this country.Centro de Investigaciones en FitopatologíaInstituto de Biotecnologia y Biologia Molecula

Occurrence of scab disease of pecan caused by Cladosporium caryigenum in Argentina

Pecan (Carya illinoinensis) is a new crop in Argentina. The planted area is expanding quickly with around 4000 h in the Pampas region. In 2007 and 2008 typical scab symptoms on seedlings and mature trees were commonly observed in La Plata. A Cladosporium-like fungus was isolated on potato dextrose agar (PDA) from surface-sterilized pecan leaves collected from the Experimental Station of UNLP. Fungus' characteristics agree with a published description of Cladosporium caryigenum (Gottwald, 1982).Centro de Investigaciones en FitopatologíaFacultad de Ciencias Astronómicas y Geofísica

Downy mildew of sweet basil (Ocimum basilicum) caused by Peronospora sp. in Argentina

In the green belt surrounding Buenos Aires and La Plata cities, Argentina, sweet basil (Ocimum basilicum) is grown commercially under greenhouse mainly for fresh consumption. In February 2008, plants showing typical symptoms of downy mildew were found in greenhouses in La Plata. The disease was widespread in the cropped area with 100% prevalence. Infection resulted in chlorotic leaves with a greyish to dark brown fungal-like growth on the lower surfaces. A sample was deposited in the local herbarium (KUS-F23241). Conidiophores were subhyaline, 230­ 460 X 7-11 pm, straight, monopodially branched, in 4-6 orders, and emergent from stomata. Ultimate branchlets were mostly in pairs, slightly curved, 10-25 (-30) pm long and had subtruncate tips. Conidia were broadly ellipsoidal to subglobose, greyish brown, and measured 24*3- 32-5 X 22-5-26-5 pm (length/width ratio = 1-06-1-23). This pathogen is unequivocally in the genus Peronospora, and well concordant with characters ofthe unnamedPeronospora speciesreported in basil (Belbahri et al., 2005).Facultad de Ciencias Agrarias y Forestale

Occurrence of scab disease of pecan caused by Cladosporium caryigenum in Argentina

Pecan (Carya illinoinensis) is a new crop in Argentina. The planted area is expanding quickly with around 4000 h in the Pampas region. In 2007 and 2008 typical scab symptoms on seedlings and mature trees were commonly observed in La Plata. A Cladosporium-like fungus was isolated on potato dextrose agar (PDA) from surface-sterilized pecan leaves collected from the Experimental Station of UNLP. Fungus' characteristics agree with a published description of Cladosporium caryigenum (Gottwald, 1982).Centro de Investigaciones en FitopatologíaFacultad de Ciencias Astronómicas y Geofísica

Leaf spot of cultivated and wild Alstroemeria spp. caused by Asperisporium alstroemeriae

Asperisporium alstroemeriae (Allesch.) Maubl., the causal agent of leaf spot on Alstroemeria spp., is recorded for the first time in Argentina on commercial hybrids and on the native species A. psittacina. It appears that cultivated hybrids of Alstroemeria spp. and A. psittacina are new hosts for this pathogen. Disease symptoms and fungal description are provided.Centro de Investigaciones en Fitopatologí

First report of Tomato blistering mosaic virus infecting tomato in Argentina

Tomato (Solanum lycopersicum) ranks as the most important crop among greenhouse-planted crops in terms of cultivated areas (17,800 ha) and production in Argentina. In September 2014, farmers reported that tomato plants of cv. Elpida (Enza Zaden) showed mosaic and blistering on leaves in La Plata (Buenos Aires green-belt). The diseased plants occurred together in the same line, showing a typical pattern of mechanically transmitted pathogens. Although incidence did not exceed 1.5%, it was distributed in several distant locations within the district, posting a serious threat to the tomato production. Five samples were collected from symptomatic plants and tested for Tospovirus, Begomovirus, and Cucumber mosaic virus by reverse transcription polymerase chain reaction (RT-PCR) (Dewey et al. 1996), PCR (Rojas et al. 1993), and enzyme-linked immunosorbent assay (ELISA), respectively. All results were negative. The samples were then examined under transmission electron microscopy. Isometric virus-like particles of 25 to 30 nm in diameter were seen in leaf-dip preparations, and isometric virus-like particles aggregated in the cytoplasm of mesophyll cells and alterations of chloroplast membrane in association to virus-like particles were observed in ultrathin sections suggesting a Tymovirus. To identify this virus, leaf and stem samples were dot blotted on a nitrocellulose membrane and incubated with Tomato blistering mosaic virus (ToBMV) antiserum, kindly provided by Dr. Alice K. Inoue-Nagata (Embrapa-Horticulture, Brazil). The samples reacted to the ToBMV antiserum, indicating the presence of ToBMV or a ToBMV-related virus. Sap of the diseased samples was used to inoculate tomato cv. Elpida and several indicator plants (Datura stramonium, Nicotiana benthamiana, Nicotiana tabacum cv. TNN, Capsicum annuum cv. Almuden, and Chenopodium quinoa). The inoculated tomato plants showed foliar chlorosis, mosaic, necrosis, and blistering similar to those observed in the greenhouses, and the indicator plants reproduced the symptoms reported by de Oliveira et al. (2013). Furthermore, two samples were subjected to RT-PCR using primers specifically designed to amplify the complete capsid protein (CP) from ToBMV: TymoF3RaceFor, 5′-TCCAATCCATGCCTTTTGAT-3′; and ToBMV3EndNdeIRev, 5′-TTCATATGGTTTCCGATACCCTCGG-3′. DNA fragments of expected size (1000 bp) were amplified, cloned in pGEM-T easy (Promega), and sequenced. Sequence analysis showed the nucleotide sequences of the two isolates were identical, suggesting that they are the same variant (Accession No. KT235894). This isolate shares 92% identity with tomato isolate SC50 (Nicolini et al. 2015) and tobacco isolate BR001 (Melo et al. 2014), both from Brazil. These results indicate that the tomato disease in Buenos Aires green-belt is caused by ToBMV. To our knowledge, this is the first report of ToBMV infecting tomato in Argentina. This finding has an important epidemiological impact because ToBMV represents a new problem to tomato crops in this country.Centro de Investigaciones en FitopatologíaInstituto de Biotecnologia y Biologia Molecula

Pseudomonas populations causing pith necrosis of tomato and pepper in Argentina are highly diverse

Pseudomonas species causing pith necrosis symptoms on tomato and pepper collected in different areas of Argentina were identified as Pseudomonas corrugata, P. viridiflava and Pseudomonas spp. Their diversity was analysed and compared with reference strains on the basis of their phenotypic characteristics, copper and antibiotic sensitivity tests, serology, pathogenicity, DNA fingerprinting and restriction fragment length polymorphism (RFLP) analysis of a 16S rRNA gene fragment. All P. corrugata strains tested were copper-resistant while P. viridiflava strains were more variable. Numerical analysis of phenotypic data showed that all P. corrugata strains formed a single phenon that clustered at a level of about 93%, while all the P. viridiflava strains clustered in a separated phenon at a level of 94%. Genomic analysis by repetitive (rep)-PCR and 16S rRNA-RFLP fingerprinting and serological analysis showed that the two species contained considerable genetic diversity. Inoculations of tomato and pepper plants with strains from both hosts caused similar pith necrosis symptoms. Strains of both P. corrugata and P. viridiflava were grouped according to their geographical origin and not according to the original host. This is the first report of Pseudomonas viridiflava causing pith necrosis on pepper.Facultad de Ciencias Agrarias y ForestalesInstituto de Biotecnologia y Biologia Molecula

Corynespora cassiicola and Stemphylium lycopersici infection and disease development on tomatoes in Argentina

Two pathogens were isolated from tomatoes with severe chlorosis and necrosis in northwestern Argentina. Monosporic cultures were morphologically characterised and molecularly identified as Stemphylium lycopersici and Corynespora cassiicola. This is the first report of C. cassiicola infecting tomato in Argentina.Fil: Franco, Mario Emilio Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; ArgentinaFil: López, Silvina Marianela Yanil. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; ArgentinaFil: Lucentini, Cesar Gustavo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; ArgentinaFil: Troncozo, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Saparrat, Mario Carlos Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Instituto de Botánica Spegazzini; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Ronco, Blanca Lía. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; ArgentinaFil: Balatti, Pedro Alberto. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; Argentin