Polyclonal rabbit antisera were produced to the coat protein of Bean golden mosaic virus Brazil isolate (BGMV), Cabbage leaf curl virus (CabLCV), Tomato yellow leaf curl virus (TYLCV), and Tomato mottle virus (ToMoV), all expressed in Escherichia coli by the pETh expression vector. The expressed coat protein of each virus was purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for use as an immunogen. The antisera to BGMV, CabLCV, TYLCV, and ToMoV reacted in indirect (plate-trapping) enzyme-linked immunosorbent assay (ELISA) with extracts from begomovirus-infected tissue. The antisera to BGMV, CabLCV, TYLCV, and ToMoV also reacted specifically with the test begomovirus antigens in leaf imprint blots and Western blots. The CabLCV and TYLCV antisera were used to detect Bean golden yellow mosaic virus antigens by immunogold labeling of thin sections of infected bean tissues. In tissue blot immunoassays, the TYLCV antiserum reacted well with TYLCV antigens but not with ToMoV antigens, while CabLCV antiserum reacted well with ToMoV antigens and weakly with TYLCV antigens. The results indicate that polyclonal antisera prepared to expressed begomovirus coat proteins were useful for the detection of begomoviruses in an array of assays.

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In September 2002, several unthrifty Verbena canadensis ‘Homestead purple’ plants were received at the Division of Plant Industry in Gainesville, FL. Symptoms included very subtle yellowing and distortion or stunting of the younger leaves, symptoms that could be overlooked as a nutritional problem. Symptomatic leaves were ground in phosphate buffer and mechanically inoculated to a variety of plants that included Antirrhinum majus, Chenopodium amaranticolor, Datura stramonium, Gomphrena globosa, Pisum sativum, Trifolium pratense, T. repens, Vicia faba, and Vigna unguiculata. These hosts showed symptoms similar to those described for infection by Clover yellow mosaic virus (ClYMV) (3). In addition, the virus systemically infected Arachis hypogaea, Catharanthus roseus, C. quinoa, Nicotiana benthamiana, and healthy seed-grown Verbena × hybrida. No symptoms were seen in inoculated Zinnia elegans, N. glutinosa, N. clevelandii, Lycopersicon esculentum, Cucumis sativus, or Capsicum annuum. However, back inoculations of Cucumis sativus to C. amaranticolor gave typical local and systemic symptoms. Microscopic examination of leaf strips of infected V. faba revealed banded inclusions typical of the genus Potexvirus (1). Reverse-transcription polymerase chain reaction (RT-PCR) using degenerate primers for the genus Potexvirus (2) produced a 750-bp product that is the expected product for the genus Potexvirus. The RT-PCR product was cloned in pGem-T easy (Promega, Madison, WI) and sequenced. BLAST ( http://www.ncbi.nlm.nih.gov/ BLAST/ ) analysis of the sequence showed an 82% identity at the nucleotide level with the RNA polymerase gene of ClYMV. Leaf extracts of the original verbena, several inoculated hosts, and a known sample of ClYMV in N. benthamiana were tested in sodium dodecyl sulfate immunodiffusion (4) against antiserum to the degraded capsid protein of ClYMV. A reaction of identity was seen with infected samples but not with samples for comparable virus-free plants. To our knowledge, this is the first time this virus has been found in the eastern United States. It is not known how or if the presence of this noninsect transmitted virus in an ornamental will affect the agricultural, forage, or ornamental industries in the east or how widely distributed Verbena sp. infected with this virus may be at this time. References: (1.) R. G. Christie and J. R. Edwardson. Fla. Agric. Exp. Stn. Monogr. 9, 1994. (2.) A. Gibbs et al. J. Virol. Methods 74:67,1998 (3.) M. J. Pratt. Can. J. Bot. 39:655. 1961. (4) D. E. Purcifull and D. L. Batchelor. Fla. Agric. Ext. Stn. Bull. 788, 1977.

Bacterial leaf spot of watermelon caused by Pseudomonas syringae has been an emerging disease in the southeastern United States in recent years. Disease outbreaks in Florida were widespread from 2013 to 2014 and resulted in foliar blighting at the early stages of the crop and transplant losses. We conducted a series of field trials at two locations over the course of two years to examine the chemical control options that may be effective in management of this disease, and to investigate the environmental conditions conducive for bacterial leaf spot development. Weekly applications of acibenzolar-S-methyl (ASM) foliar, ASM drip, or copper hydroxide mixed with ethylene bis-dithiocarbamate were effective in reducing the standardized area under the disease progress curve (P < 0.05). Pearson’s correlation test demonstrated a negative relationship between the average weekly temperature and disease severity (–0.77, P = 0.0002). When incorporated into a multiple regression model with the square root transformed average weekly rainfall, these two variables accounted for 71% of the variability observed in the weekly disease severity (P < 0.0001). This information should be considered when choosing the planting date for watermelon seedlings as the cool conditions often encountered early in the spring season are conducive for bacterial leaf spot development.