First Report of the Plum Pox Virus Recombinant Strain on Peach in Bulgaria.

Plum pox virus (PPV) causes sharka, the most damaging viral disease of stone fruit species. Seven distinct PPV strains are known; PPV-M, PPV-D, and PPV-Rec are the most common (3). PPV-Rec is a unique recombinant (3) between PPV-M and PPV-D and has been reported from plum, apricot, Japanese plum, myrobalan, and blackthorn in eastern and central Europe, but has never been found in peach as a single natural infection (2). A survey was conducted during spring 2009 in eight peach orchards located in the southwest, southeast, and south central regions of Bulgaria to assess the incidence of PPV infection. A total of 98 leaf samples from individual trees showing PPV-like symptoms were collected and analyzed by triple-antibody sandwich (TAS)-ELISA with the universal monoclonal antibody (MAb) 5B (Agritest, Valenzano, Italy). Sixty one samples reacted positive for PPV (optical density 0.161 to 1.267) and these samples were further analyzed with PPV-M (AL) and PPV-D (4DG5) specific MAbs (1). All 61 samples reacted positively with PPV-M specific MAbs. To distinguish PPV-M and PPV-Rec strains, which are serologically identical, immunocapture (IC)-reverse transcription (RT)-PCR was carried out with PPV-M (CIP-M: 5'-GTC GCA GCA TTT GTA GCC CTT GTT-3', CIP-MR: 5'-CCA ACA CGT TAA CGC CAT GCT TCA-3') and PPV-D (CIP-D: 5'-ATG ATG CTG TTT GAC TCG GAG CGA-3', CIP-DR: 5'-TCG CAA CTG CTT GCA CAC ATT CTC-3') specific primers targeting the 6K1-CI genomic region. A PCR fragment of ~880 bp amplified with PPV-M specific primers obtained from 59 samples confirmed that these were PPV-M isolates. However, the remaining two samples (both coming from infected tress located in two different orchards in the southwest region) yielded a 468-bp PCR fragment with PPV-D specific primers, suggesting that these two samples belonged to PPV-Rec strain. These samples together with controls of PPV-M, PPV-D, and PPV-Rec strains were further analyzed by RT-PCR using mD5/mM3 primers spanning the recombination breakpoint (4). Both peach samples and the PPV-Rec strain control produced a single 605-bp PCR product. The two peach amplicons were purified and sequenced directly with the same primers. The nucleotide (nt) sequences obtained were 100% identical to each other. BLAST analysis of the two samples with PPV-Rec (No. AF421118.1) showed maximum nt identity of 98%. Percent maximum nt identity with PPV-M (No. AY324837.1) and PPV-D (No. AB576062.1) were 93 and 87%, respectively. The deduced amino acid sequences of the two isolates were 98% identical to PPV-Rec (No. No. AF421118.1), 93% identical to PPV-M (No. M92280.1), and 84% identical to PPV-D (No. AB576062.1). Analyzed samples were further transmitted from the diseased trees to peach seedlings (GF 305) by chip-budding in a greenhouse during the fall of 2009. Six months later, faint vein clearing on the leaves of inoculated seedlings was observed. The presence of PPV was confirmed by TAS-ELISA and PPV-Rec presence was shown by IC-RT-PCR (mD5/mM3 primers). One of the generated 605-bp products was sequenced and showed 100% nt identity with the isolate used for inoculation. To our knowledge, this is the first identification of PPV-Rec strain in naturally infected peach trees, a finding that calls for further large-scale investigations of PPV-Rec incidence in peach in Bulgaria. References: (1) M. Cambra et al. OEPP/EPPO Bull. 24:569, 1994. (2) S. Dallot et al. Acta Hortic. 781:227, 2008. (3). M. Glasa et al. J. Gen. Virol. 85:2671, 2004. (4) Z. Subr et al. Acta Virol. 48:173, 2004.

Biocompatible zwitterionic copolymer networks with controllable swelling and mechanical characteristics of their hydrogels.

The equilibrium swelling ratio in both water and physiological solution of the biocompatible copolymer networks of 3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate (DMAPS) and N-vinyl-2-pyrrolidone (NVP) is determined as a function of copolymer composition. It is established that equilibrium swelling ratio of the polymer networks in physiological solution increase with raise of zwitterionic monomer unit fraction. A sharp decrease of this ratio in water with increase of zwitterionic monomer unit fraction is related to the formation of thermolabile physical junctions produced by dipole-dipole interactions between the zwitterionic side groups. The same fact affects considerably the storage and loss moduli of the copolymer hydrogels as well as the morphology of the dried networks. Scanning electron microscopy images provided evidence of the occurrence of a lamellar structure forming the morphology of the polymers. This was corroborated by differential scanning calorimetry experiments. In this way a possibility for effective control on swelling ratio in different solutions and the mechanical properties of these novel biocompatible networks are established.

Bidens mottle virus Identified in Tropical Soda Apple in Florida.

Tropical soda apple (TSA) (Solanum viarum Dunal), a plant native to South America, was first identified in Florida in 1988 (4). It rapidly became a noxious weed in pastures throughout the state and it is known to be a reservoir for Cucumber mosaic virus, Potato leafroll virus, Potato virus Y (PVY), Tobacco etch virus (TEV), Tomato mosaic virus, and Tomato mottle virus, viruses that infect important vegetable crops in Florida (3). During a routine survey of Florida weeds during May of 2004, a TSA plant with chlorotic, young leaves found near Okeechobee, FL was determined to be infected with a potyvirus by using a commercially available enzyme linked immunosorbent assay kit (Agdia, Elkhart, IN). The results of a host range study indicated this potyvirus was neither PVY nor TEV. The virus caused local lesions in Chenopodium amaranticolor and systemic symptoms in C quinoa, Coreopsis sp. (C. A. Baker, unpublished), Helianthus annus, Nicotiana benthamiana, Petunia × hybrida, Verbena hybrida, and Zinnia elegans. It did not infect Gomphrena globosa, N. glutinosa, Pisum sativum, or Phaseolus vulgaris (1). Cylindrical inclusions consistent with those observed in plants infected with Bidens mottle virus (BiMoV) were observed in Z. elegans. Immunodiffusion tests with antiserum to BiMoV (Department of Plant Pathology, University of Florida) gave a reaction of identity with leaf extracts of the symptomatic zinnia, a known sample of BiMoV originally isolated from Bidens pilosa and a recent isolate of BiMoV from lettuce in Belle Glade, FL (C. A. Baker and R. Raid, unpublished). A partial polyprotein gene fragment (GenBank Accession No. EF467235) was amplified from total RNA of an inoculated C. quinoa plant by reverse transcription (RT)-PCR with previously described degenerate potyvirus primers (2). Analysis of the RT-PCR product sequence confirmed the host range results and indicated that the potyvirus infecting TSA was neither PVY nor TEV. However, the nucleotide and deduced amino acid sequences of a 247-bp portion of the RT-PCR product were 94 and 98% identical, respectively, with the coat protein sequence (GenBank Accession No. AF538686) of Sunflower chlorotic spot virus (SCSV). SCSV is a tentative potyvirus species described from Taiwan that is not yet recognized as an accepted species by the International Committee on Taxonomy of Viruses. On the basis of our concurrent host range, inclusion body, and serological data, it is likely that SCSV is in actuality the previously described and currently accepted potyvirus species BiMoV, for which no previous sequence data existed. As part of a comprehensive viral disease management plan, it is recommended that TSA plants growing in and around lettuce-production areas be controlled along with other weed hosts of this virus. References: (1) A. A. Brunt et al., eds. Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 20 at http://biology.anu.edu.au/Groups/MES/vide/ , 1996. (2) A. Gibbs and A. J. Mackenzie. Virol. Methods 63:9, 1997. (3) R. J. McGovern et al. Int. J. Pest Manag. 40:270, 1994. (4) J. J. Mullahey et al. Weed Technol. 7:783, 1993.