Seasonal phenology of Amphorophora agathonica (Hemiptera: Aphididae) and spread of viruses in red raspberry in Washington.

Amphorophora agathonica (Hottes) is the primary vector of aphid-transmitted viruses in red raspberry in the Pacific Northwest region of the United States. To better understand the biology of the aphid, we estimated the lower developmental threshold and studied the seasonal activity of A. agathonica in commercial fields in northern Washington state. In addition, we monitored the spread of raspberry viruses (raspberry latent virus and raspberry leaf mottle virus, RLMV) to determine how rapidly fields became infected and whether there was a relationship between aphid presence and infection. The lower developmental threshold of A. agathonica was estimated to be 2.7°C. In the field, apterous and alate aphid populations began rapidly increasing at ≍800 growing degree-days and peaked at 1,050 growing degree-days. RLMV spread rapidly, with 30-60% of plants in four different commercial fields testing positive after three growing seasons. There was no discernible relationship between the presence or abundance of aphids based on 10 leaves sampled per plant location, and the odds of that plant becoming infected with RLMV.

A raspberry bushy dwarf virus isolate from Ecuadorean Rubus glaucus contains an additional RNA that is a rearrangement of RNA-2.

Sequencing of the complete genome of a raspberry bushy dwarf virus isolate from Rubus glaucus in Ecuador revealed that its RNA-1 and RNA-2 were 5449 and 2231 nucleotides (nt) long, respectively, and phylogenetically closest to isolates from Sweden and Slovenia. In dsRNA analysis of infected plants, an additional band of 3 kbp was observed. Sequencing of this band revealed that it was 3279 nt long. BLAST searches revealed that this band contained a modified version of RNA-2, which consisted of RNA-2 (2231 nt) plus an additional 1048-nt fragment that was concatenated in a reverse-complement fashion to its 5' terminus.

First Report of Banana bract mosaic virus in 'Cavendish' Banana in Ecuador.

Banana bract mosaic virus (BBrMV), a member of the genus Potyvirus, family Potyviridae, is the causal agent of bract mosaic disease. The disorder has been considered a serious constraint to banana and plantain production in India and the Philippines, where the virus was first identified (3). To date, the presence of BBrMV has been reported only in a few banana-growing countries in Asia (3). In the Americas, BBrMV has been detected by ELISA tests in Colombia only (1). The efficient spread of BBrMV through aphids and vegetative material increases the quarantine risk and requires strict measures to prevent entrance of the virus to new areas. In Ecuador-the world's number one banana exporter-the banana industry represents the main agricultural income source. Thus, early detection of banana pathogens is a priority. In June of 2012, mosaic symptoms in bracts and bunch distortion of 'Cavendish' banana were observed in a commercial field in the province of Guayas, Ecuador. Leaves from 35 symptomatic plants were tested for Cucumber mosaic virus (CMV), Banana streak virus (BSV), and BBrMV using double antibody sandwich ELISA kits from Adgen (Scotland, UK). Twenty-one plants tested positive for BBrMV but not for CMV or BSV. In order to confirm the ELISA results, fresh or lyophilized leaf extracts were used for immunocapture reverse transcription (IC-RT)-PCR. In addition, total RNA was extracted from the ELISA-positive samples and subjected to RT-PCR. The RT reactions were done using both random and oligo dT primers. Several sets of primers, flanking conserved regions of the virus coat protein (CP), have been used for PCR-detection of BBrMV (2,3,4). The Ecuadorian BBrMV isolate was successfully detected by three primer sets with reported amplification products of 324, 280, and 260 nucleotides long, respectively (3,4). Amplification products of the expected size were purified and sequenced. All the nucleotide sequences obtained from 20 PCR-positive symptomatic plants were 100% identical between each other. However, 99% identity was observed when PCR products from the Ecuadorian isolate were compared with the corresponding fragment of a BBrMV isolate from the Philippines (NCBI Accession No. DQ851496.1). PCR products of the Ecuadorian isolate, amplified by the different CP primers described above, were assembled into a 408-bp fragment and deposited in the NCBI GenBank (KC247746). Further testing confirmed the presence of BBrMV in symptomatic plants from four different provinces. To our knowledge, this is the first report of BBrMV in Ecuador and the first BBrMV partial nucleotide sequence reported from the Americas. It is worth mentioning that primer set Bract 1/Bract 2, which amplifies a 604-bp product (2), was not effective in detecting the Ecuadorian isolate. It is hypothesized that nucleotide variation at the reverse primer site is the cause of the lack of amplification with this primer set, since the forward primer is part of the sequenced product and no variation was found. Sequencing of the entire CP region is underway to conduct phylogenetic analysis and determine genetic relationships across several other BBrMV isolates. References: (1) J. J. Alarcon et al. Agron 14:65, 2006. (2) M. F. Bateson and J. L. Dale. Arch. Virol 140:515, 1995. (3) E. M. Dassanayake. Ann. Sri Lanka Dept. Agric. 3:19, 2001. (4) M. L. Iskra-Caruana et al. J. Virol. Methods 153:223, 2008.

First Report of Raspberry bushy dwarf virus in Andean Blackberry (Rubus glaucus) in Central Ecuador.

During the past two decades, several viruses have been identified from Rubus spp. in wild and commercial plantings around the world (2). In Ecuador, approximately 14 tons of blackberries are produced each year from an estimated area of 5,500 ha. In 2012, a preliminary survey was conducted to determine the presence of RNA viruses in Rubus glaucus, the most prevalent blackberry in Ecuador. Fifteen plants showing leaf mottling and severe mosaic were leaf-sampled from each of five different fields in Azuay Province. A total of 12 pooled samples of 20 g were obtained from the collected symptomatic tissue and used for dsRNA extraction using a cellulose-based protocol for detection of RNA viruses in plants (3). Three dsRNA segments of approximately 5 kbp, 2 kbp, and 900 bp were observed from all 12 dsRNA preparations. The dsRNA was heat-denatured and used as template for the generation of cDNA library using the universal random primer 5'-GCCGGAGCTCTGCAGAATTCNNNNNN-3', for reverse transcription (RT), and the anchor primer 5'-GCCGGAGCTCTGCAGAATTC-3'for PCR as described (1). The PCR products were cloned using a StrataClone Kit (Agilent, CA) and sequenced (Macrogen, Korea). Sequence analysis revealed the presence of Raspberry bushy dwarf virus (RBDV), a pollen-borne Idaeovirus naturally found in several Rubus spp. worldwide. Approximately 120 RBDV sequences obtained from the Ecuadorean isolate were assembled into two contigs belonging to RNA1 and RNA2. Both sequences were re-confirmed by RT-PCR using specific primers. Partial sequences were assigned GenBank Accessions KC315894, KC315893, and KC315892 for the replicase, MP and CP, respectively. Furthermore, BLAST searches showed that the nucleotide sequence corresponding to the replicase was 95% similar to an isolate from the resistance breaking R15 strain (S51557.1), whereas the MP and CP nucleotide sequences were up to 98% similar to a Slovenian isolate (EU796088.1). Primers designed to amplify a 427-bp portion of the CP were used to detect RBDV from four blackberry plantings in two distant production areas: Ambato in Tungurahua Province and Paute in Azuay Province. Leaf mottling and severe mosaic was observed in 90% of blackberry fields in those two locations. Leaf samples (n = 90) were randomly collected from both symptomatic and asymptomatic plants in each location. In Ambato, RBDV was detected in 50% and 40% of symptomatic and asymptomatic plants, respectively. In Paute, RBDV was present in 70% of symptomatic plants and 29% of asymptomatic plants. The presence of RBDV in asymptomatic plants suggests the virus might not be the sole causal agent of the disorder. Further studies are needed to determine the role of RBDV in the observed symptoms, since virus complexes responsible for increased severity of symptoms have been commonly reported in Rubus spp. (4). R. glaucus is native to the tropical highlands (from Ecuador to Mexico) and differs from blackberries commercially grown in the United States and Europe. Therefore, RBDV-induced symptoms reported in blackberry grown in the United States and Europe may not be extrapolated to the Andes berry. To the best of our knowledge, this is the first report of RBDV from blackberry in Ecuador. References: (1) P. Froussard. Nucleic Acids Res. 20:2900, 1992. (2) R. R. Martin et al. Plant Dis. 97:168, 2013. (3). T. J. Morris and J. A. Dodds. Phytopathology 69:854. 1979. (4) D. F. Quito-Avila et al. J. Virol. Methods 179:38, 2012.