First Report of Beet necrotic yellow vein virus on Red Table Beet in Brazil.

Beet necrotic yellow vein virus (BNYVV) is an economically important pathogen of sugar beet (Beta vulgaris var. saccharifera) in several European, and Asian countries and in the United States (3). The virus is transmitted by the soil-inhabiting plasmodiophorid Polymyxa betae and causes the rhizomania disease of sugar beet. In November 2012, plants of B. vulgaris subsp. vulgaris cv. Boro (red table beet) exhibiting mainly severe characteristic root symptom of rhizomania were found in a commercial field located in the municipality of São José do Rio Pardo, State of São Paulo, Brazil. No characteristic virus-inducing foliar symptom was observed on diseased plants. The incidence of diseased plants was around 70% in the two visited crops. As the hairy root symptom is indicative of infection by BNYVV, the present study aimed to detect and identify this virus associated with the diseased plants. Preliminary leaf dip analysis by transmission electron microscopy revealed the presence of very few benyvirus-like particles. Total RNA was extracted from roots of three symptomatic plants and one asymptomatic plant according to Toth et al. (3). One-step reverse-transcription-polymerase chain reaction (RT-PCR) was performed as described by Morris et al. (2) with primers that amplify part of the coat protein gene at RNA2. The initial assumption that the hairy root symptom was associated with BNYVV infection was confirmed by the amplification of a fragment of ~500 bp from all three symptomatic samples. No amplicon was obtained from the asymptomatic control plant. Amplicons were directly sequenced, and the consensus nucleotide and deduced amino acid sequences showed 100% identity. The nucleotide sequence for one amplicon (Accession No. KM433683) was compared with other sequences deposited in GenBank. The nucleotide (468 nt) and deduced amino acid (156 aa) sequences shared 93 to 100 and 97 to 99% identity, respectively with the corresponding nucleotide and amino acid sequences for other isolates of type A of BNYVV. The virus was transmitted to three of 10 red table beet plants inoculated with contaminated soil, and infection was confirmed by nested RT-PCR, as described by Morris et al. (1), and nucleotide sequencing. This is the first report on the occurrence of BNYVV in Brazil, which certainly will affect the yield of red table beet in the producing region. Therefore, mapping of the occurrence of BNYVV in red table beet-producing areas in Brazil for containment of the spread of the virus is urgent. In the meantime, precautions should be taken to control the movement of contaminated soil and beet roots, carrots, or any vegetable grown on infested land that might introduce the virus to still virus-free regions. References: (1) J. Morris et al. J. Virol. Methods 95:163, 2001. (2) D. D. Sutic et al. Handbook of Plant Virus Diseases. CRC Press, Boca Raton, Florida, 1999. (3) I. K. Toth et al. Methods for the Detection and Quantification of Erwinia carotovora subsp. atroseptica (Pectobacterium carotovorum subsb. atrosepticum) on Potatoes: A Laboratory Manual. Scottish Crop Research Institute, Dundee, Scotland, 2002.

First Report of Cowpea aphid-borne mosaic virus on Sesame in Paraguay.

Sesame (Sesamum indicum L.) is cultivated mainly in the central region of the Departamento de San Pedro in Paraguay from October to February and the seed are exported to Asia. The crop is grown on 100,000 ha annually and Escoba blanca is the most common cultivar. The crop plays an important socioeconomical role since it is cultivated mostly by small growers. A disease characterized by yellowing and curling down leaves and shortening of the internodes has been observed in almost all sesame-growing areas. It is referred to locally as "ka'are" because the affected sesame plant resembles Chenopodium ambrosioides L. This disease occurred occasionally and was of marginal importance prior to 2005, but during the last five growing seasons the disease incidence has increased substantially, with some growers losing the entire crop. To determine the causal agent, symptomatic leaf samples were collected from five commercial fields near Colonia San Pedro and Choré, Departamento San Pedro in December 2009. Preliminary transmission electron microscopy (TEM; Zeiss EM900) of extracts from symptomatic leaves revealed the presence of elongated flexible particles resembling a potyvirus. Mechanical transmission assays resulted in chlorotic local lesions on C. quinoa and C. amaranticolor, mosaic on Vigna unguiculata and Nicotiana benthamiana, and symptoms on sesame that are similar to those observed in the field. The disease could also be reproduced in sesame by aphid (Myzus persicae) transmission in a nonpersistent manner. TEM examination of leaf sections of these naturally or experimentally infected plants showed the presence of the type I cylindrical inclusions and masses of filamentous particles. Leaf extracts of naturally or experimentally infected sesame and test plants were positive for Cowpea aphid-borne mosaic virus (CABMV) on the basis of plate-trapped antigen (PTA)-ELISA. CABMV as the causal agent of "ka'are" disease of sesame in Paraguay was further confirmed by analyzing part of the nucleotide sequence of CABMV coat protein and 3' nontranslated region that were obtained directly from reverse transcription-PCR product amplified with PV1-antisense primer (5'-gatttaggtgacactatagt17-3') and WCIEN-sense primer (5'-atggtttggtgyatygaraat-3') (1,2). Comparisons of the 676-bp nucleotide sequence of two sesame virus isolates (GenBank Accession Nos. HQ336402 and HQ336403) revealed 92% identity with the corresponding nucleotide sequence of CABMV available in the GenBank (Accession No. AF348210). Thus, all the assays indicated that the "ka'are" disease of sesame in Paraguay is caused by an isolate of CABMV. Several cowpea fields, nearby sesame diseased crops, also contained plants exhibiting mosaic symptoms. Transmission assays, electron microscopy, PTA-ELISA, and nucleotide sequence analysis indicated that they were also infected by CABMV and may play an important role in the epidemiology of this disease on sesame. CABMV isolates from passion fruit and cowpea from Brazil were mechanically transmitted to sesame but induced milder symptoms. CABMV-infected sesame was described in the United States (3), but to our knowledge, this is the first report of a severe disease on sesame caused by this virus in Paraguay. References: (1) A. Gibbs and A. Mackenzie. J. Virol. Methods 63:9, 1997. (2) L. D. C. Mota et al. Plant Pathol. 53:368, 2004. (3) H. R. Pappu et al. Arch. Virol. 142:1919, 1997.

First Report of Turnip mosaic virus on Watercress in Brazil.

Watercress (Nasturtium officinale L.), a member of the family Brassicaceae, is consumed mainly as salad. Medicinal properties have also been attributed to this species. In Brazil, watercress is grown mainly by very small farmers. The crop is primarily seed propagated and growers can harvest several times per year in an established planting. Very few diseases have been reported in this crop worldwide. In Brazil, watercress infection by Cauliflower mosaic virus (CaMV) (3), Cucumber mosaic virus (CMV) (1), and an unidentified potyvirus (2) were previously reported. In January 2009, 80% of watercress plants, cv. Gigante Redondo, exhibiting severe mosaic, leaf size reduction, and plant stunting were observed in a crop in Marechal Floriano Municipality, State of Espírito Santo, Brazil. Preliminary leaf dip analysis by transmission electron microscopy revealed the presence of potyvirus-like particles. Sap from five infected plants reacted in plate-trapped antigen (PTA)-ELISA with polyclonal antiserum against Turnip mosaic virus (TuMV), but not with antiserum against CMV. Both antisera were produced in the Plant Virology Laboratory, ESALQ/USP. Mechanically inoculated watercress plants developed similar systemic mosaic symptoms. The virus was also transmitted to Nicotiana benthamiana, which exhibited severe mosaic and stunting. The presence of TuMV on these inoculated plants was confirmed by PTA-ELISA and reverse transcription (RT)-PCR. Total RNA extracted from infected and healthy watercress and infected N. benthamiana was analyzed by RT-PCR using specific pairs of primers flanking the coat protein gene of TuMV. Degenerated anti-sense (5'-t/caacccctt/gaacgcca/cagt/ca-3') and sense (5'-gcaggtgaa/gacg/acttgat/ca/gc-3') primers were designed after analysis to an alignment of the nucleotide sequences for five isolates of TuMV available in the GenBank (Accession Nos. NC_002509, D10927, EU680574, AB362513, and D88614). One fragment of 838 bp was amplified from samples in the infected plants, but not in the healthy controls. Two amplicons were purified and directly sequenced in both directions. Comparisons of the 731-bp consensus nucleotide sequence (Accession No. HM008961) to several other isolates of TuMV revealed 94 to 95% identity in the coat protein region. To our knowledge, this is the first report of TuMV in watercress in Brazil. Management of the disease should include propagation by seeds instead of vegetative parts of the plants and rouging of diseased plants to prevent mechanical transmission during successive harvestings. References: (1) A. J. Boari et al. Fitopatol. Bras. 25:438, 2000. (2) A. J. Boari et al. Fitopatol. Bras. 27:S200, 2002. (3) M. L. R. Z. C. Lima et al. Fitopatol. Bras. 9:403, 1984.