A New Host Diagnosed with a Strain of Sugarcane mosaic virus in Florida: Red-Veined Prayer Plant (Maranta leuconeura erythroneura)

Prayer plants (Maranta spp.), which are indigenous to Brazil, are commercially produced in nurseries mainly to be sold as potted houseplants. However, in frost-free areas, they are also used as a ground cover. In March 2009, the Division of Plant Industry in Gainesville, FL received cuttings of red-veined prayer plant or red maranta (Maranta leuconeura erythroneura) from several nurseries in central Florida. The cuttings originated in Costa Rica. The presence of a viral infection was indicated by the mosaic pattern seen on the upper surface of the leaves and chlorotic lesions on the underside of leaves. Epidermal strips were taken and stained in Orange-Green (O-G) and Azure A (1). Microscopic examination revealed viral inclusions that stained only in O-G, indicating the presence of a potyvirus. Leaf dips were prepared for the electron microscope and flexuous rods consistent with a potyvirus were found. Indirect-ELISA using universal potyvirus antiserum (Agdia Inc., Elkhart, IN) confirmed the presence of a potyvirus infection. Total RNA was extracted from symptomatic tissue of five infected samples with Qiagen's RNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). Reverse transcription was conducted with the oligo d(T) primer M4T with AMV-RT at 37°C for 1 h. PCR was performed with primer M4 and a degenerate primer designed to amplify the 3′ end of all potyviruses (2). A target amplicon of 1.7 kb was produced from all five samples. Three of these samples were cloned and sequenced. Approximately 1,250 bp were sequenced from each sample. The sequenced regions include the 3′ end of the Nib gene, the complete coat protein, and the beginning of the 3′ untranslated region (UTR). The nucleotide (nt) sequences were deposited into GenBank (Accession Nos. GQ853403–GQ853405). The nt sequences of the three samples were 97 to 98% identical to each other. When compared with other potyviruses in the GenBank, the samples showed closest nt identity, 92 to 93%, with several isolates of Sugarcane mosaic virus (AJ278405, AY836523, U57357, and U57356). Of the plant species mechanically inoculated (Chenopodium amaranticolor, C. quinoa, Datura stramonium, Gomphrena globosa, Nicotiana benthamiana, and Zea mays), only Z. mays (corn) showed symptoms (a mild mosaic). The same type of viral inclusions were seen in leaf strips of infected corn as in the Maranta. The corn plant reacted positively in direct-ELISA against antiserum to Sugarcane mosaic virus (Agdia Inc.). Cuttings of infected Maranta were observed in the greenhouse and indoor situations for several months. The plants infected with Sugarcane mosaic virus lacked vigor and most eventually died. ELISA tests done on a few surviving plants were positive for Sugarcane mosaic virus, but the results were inconsistent, indicating a possible low titer of virus in the plants as they were dying. To our knowledge, this is a new host for Sugarcane mosaic virus, but it does not appear that Maranta will become a significant new reservoir of this virus for sugarcane or corn growers. However, infected cuttings can greatly decrease the production of this plant as an ornamental. References: (1) J. R. Edwardson and R. G. Christie. Univ. Fla. Inst. Food Agric. Sci. Bull. 894, 1966. (2) A. Gibbs and A. Mackenzie. J. Virol. Methods 63:9, 1997.

First Report of Botrytis cinerea Causing Gray Mold of Pomegranate (Punica granatum) in Greece

Pomegranate is rapidly increasing in production in Greece. During August of 2008 in the region of Larisa (central Greece), preharvest fruit rot was observed on pomegranate (cv. Kapmaditika) that caused losses estimated at 10%. Symptoms first appeared as small spots on the fruits that later increased in size and developed into expanded, dark brown lesions. Internally, tissues were soft and brown with gray mycelia and conidiophores observed. Affected fruits decayed completely during 2 months of storage (5 to 6°C), causing yield losses of up to 20%. To isolate the casual agent, conidia and conidiophores were scraped aseptically from the internal tissues, suspended in sterile water, and streaked onto the surface of potato dextrose agar (PDA). Single hyphal tips were transferred to PDA, and the isolated fungus was identified as Botrytis cinerea Pers.:Fr. on the basis of morphological characteristics (2). B. cinerea was consistently isolated from symptomatic tissues. Colonies of B. cinerea on PDA were at first colorless and became gray to brown with the development of lemon-shaped conidia (average 7.5 × 9 μm). Sclerotia were black and varied in size (1.4 to 4.5 × 1.5 to 2.7 mm) and shape (2). Pathogenicity of the isolated fungus was tested by wound inoculating five mature pomegranate fruits (cv. Kampaditika) after surface sterilization with 5% sodium hypochlorite. Plugs of the fungus (5 mm in diameter) obtained from the colony margins were transferred onto a 3- × 3-mm wound on the surface of sterilized fruit. Sterile PDA plugs were used to inoculate five control pomegranate fruits. Fruit were incubated at 22°C and 80% relative humidity in the dark. Extensive decay, similar to that observed on diseased fruits in the field, was observed on inoculated fruits 7 days after inoculation, whereas control fruits showed no decay. The pathogen was reisolated from internal rotten tissues of inoculated fruit, but not from the noninoculated control fruits. Fruit rot of pomegranate caused by B. cinerea has been reported previously in the United States (1) and China (3). However, to our knowledge, this is the first report of B. cinerea causing gray mold of pomegranate in Greece. References: (1) A. M. French. California Plant Disease Host Index. Calif. Dept. Food Agric., Sacramento, 1989. (2) W. B. Hewitt. Compendium of Grape Diseases. American Phytopathological Society, 1994. (3) Z. Zhang. Flora Fungorum Sinicorum 26:277, 2006.

Tomato spotted wilt virus Found in Five Species of the genus Tragopogon in a Florida Greenhouse

An obviously unhealthy plant identified as Tragopogon mirus Ownbey (remarkable goatsbeard) was sent for diagnosis to the Division of Plant Industry (DPI), Gainesville, FL in May of 2008. T. mirus is a recently formed allotetraploid that has T. dubius Scop. and T. porrifolius L. (goatsbeard or salsify) as parents. The parents (family Asteraceae) are diploid and originate from Eurasia. They were introduced to the northwest United States in the early 1900s. The allotetraploid T. mirus, which does not occur in Eurasia, was discovered in 1949 and named in 1950. It has been found in the northwest states of Washington and Idaho. It has also been found in Arizona (4). The plant sent to the DPI was grown in a greenhouse for research purposes at the Botany Department of the University of Florida (Alachua County). Symptoms exhibited on the leaves included mottling, chlorotic and necrotic spots, and mild distortion. Epidermal leaf strips from a mottled leaf were stained with the Orange-Green protein stain and Azure A nucleic acid stain (1). With a light microscope, granular inclusions typical for Tomato spotted wilt virus (TSWV) (1) were seen in leaf strips from both stains. The remainder of the leaf was ground in buffer and tested serologically for TSWV by TSWV-specific ImmunoStrips (Agdia, Elkhart, IN). The ImmunoStrip was positive for the presence of TSWV. This test was confirmed by double-antibody sandwich-ELISA using antiserum and conjugate for TSWV (Agdia). Further serological testing of other Tragopogon species with similar symptoms growing in the same greenhouse revealed that T. miscellus (another recently formed allotetraploid found in the northwestern United States; parents T. dubius and T. pratensis), T. dubius, T. porrifolius, and T. pratensis were also infected with TSWV. Total RNA was extracted from symptomatic leaves of T. mirus, T. dubius, T. porrifolius, and T. miscellus. Reverse transcription-PCR was performed with universal tospovirus primers BR60 and BR65 that amplify part of the nucleocapsid protein gene (2). Target amplicons of 454 bp were produced for all four samples. The PCR product from T. porrifolius was cloned and sequenced. The resulting sequence (GenBank Accession No. FJ655913) shows high homology, 98%, to several isolates of the Tomato spotted wilt virus deposited in the GenBank (Accession Nos. AY870391, AY744477, and AF020659). T. porrifolius has been reported to be naturally infected with TSWV in Italy (3); however, to our knowledge, this is the first report of this virus in the allotetraploids T. mirus and T. miscellus and in the diploids T. dubius and T. pratensis. This report adds five new Asteraceae weeds to the list of possible reservoirs of TSWV in the United States. References: (1) J. R. Edwardson and R. G. Christie. Univ. Fla. Inst. Food Agric. Sci. Bull. 894. 1996. (2) M. Eiras et al. Fitopatol. Bras. 26:170, 2001. (3) G. Parrella et al. J. Plant Pathol. 85:227. 2003. (4) D. E. Soltis et al. Biol. J. Linn. Soc. 82:2004.

Verticillium Wilt of African Daisy (Osteospermum sp.) in Italy Caused by Verticillium dahliae

During the winter of 2004, container-grown African daisy (Osteospermum sp.) plants, cv Seaside, showing symptoms of a wilt disease were observed in an open field in Albenga located in northern Italy. Symptoms were first observed on 120-day-old plants grown in a peat/composted bark/clay/pumice (50:20:10:20) substrate. The vascular tissues of affected plants appeared brown. These plants were stunted and developed yellow leaves with brown or black streaks in the vascular tissue. Verticillium dahliae was consistently and readily isolated from symptomatic vascular tissue when cultured on potato dextrose agar. Healthy rooted plants (40-day-old cv Seaside) were inoculated by root dip with a conidial suspension (5 × 107 CFU/ml) from one of three isolates of V. dahliae isolated from infected plants and transplanted into pots filled with steam-sterilized soil. Noninoculated plants served as control treatments. Plants (10 per treatment) were grown in a glasshouse at an average temperature of 25°C. First wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 15 days on each inoculated plant and become very evident after 50 days. Noninoculated plants remained healthy. V. dahliae was consistently reisolated from inoculated plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of V. dahliae on Osteospermum sp. in Italy and in Europe. Verticillium wilt has been previously reported on O. fruticosum in California (1). Reference: (1) A. M. French. California Plant Disease Host Index. Calif. Dep. Food Agric. 1989.