Aphis glycines as a Vector of Persistently and Nonpersistently Transmitted Viruses and Potential Risks for Soybean and Other Crops.

The recently introduced soybean aphid (Aphis glycines), which is widespread in the soybean-growing regions in the United States, is the only aphid able to develop large colonies on soybean. Although its potential as a vector of plant viruses is recognized, reports on virus transmission efficiency by this aphid species are limited. In the present study, we examined the ability of A. glycines to transmit several economically important viruses. The results showed that A. glycines transmitted the potyviruses Bean yellow mosaic virus (BYMV) and Soybean mosaic virus from soybean to soybean more efficiently than Myzus persicae. However, M. persicae transmitted the alfamovirus Alfalfa mosaic virus and the potyviruses Tobacco etch virus (TEV) and Tobacco vein mottling virus (TVMV) from tobacco to tobacco more efficiently than A. glycines. This is the first report to demonstrate that the soybean aphid can vector TEV and TVMV, two economically important tobacco viruses. This also is the first report to document successful transmission of BYMV by A. glycines. All attempts to transmit the nepovirus Tobacco ringspot virus by A. glycines were unsuccessful, regardless of the length of the acquisition and inoculation feeding periods. Although the luteovirus Soybean dwarf virus (SbDV) was widely distributed in red and white clover in Kentucky, it was not detected in soybean. All transmission experiments of SbDV by A. glycines were unsuccessful. A reverse-transcription polymerase chain reaction (RT-PCR) assay was developed to detect SbDV in single aphids using a pair of primers designed to amplify a 372-bp PCR fragment in the coding region of SbDV coat protein. Although A. glycines was not a vector of SbDV, the virus was detected in 100% of tested aphids by RT-PCR after a 24- to 48-h virus acquisition access feeding. The practical applications of RT-PCR in detecting persistently transmitted viruses are discussed.

The route of tomato spotted wilt virus inside the thrips body in relation to transmission efficiency.

The route of tomato spotted wilt virus (TSWV) in the body of its vectors, Frankliniella occidentalis and Thrips tabaci (Thysanoptera: Thripidae) was studied during their development. First instar larvae were allowed, immediately upon hatching, to acquire virus from mechanically infected Datura stramonium plants for 24 h. The rate of transmission by adults was determined in inoculation access feeding test on Emilia sonchifolia leaf disks. Thrips tissues were analysed for infection at 24 h intervals after the acquisition-access feeding period, and assayed by the whole-mount immuno-fluorescent staining technique. The virus was initially detected in the proximal midgut region in larvae of both species, and then in the second and third midgut regions, foregut, and salivary glands. Occasionally the first infections of the salivary glands were already detected in one-day-old second stage larvae. The intensity of the infection in the various organs of the thrips of each species was positively related to the transmission efficiency. In both thrips populations good agreement was found between the percentage of second instar larvae and adults with at least one infected salivary gland lobe and the percentage of transmitting adults. These results support the contention that the virus must reach the salivary glands before thrips pupation in order to be transmitted by old second instar larvae and adults.

Distribution and Transmission of Iris yellow spot virus.

Iris yellow spot virus (IYSV), a new tospovirus associated with a disease in onion (Allium cepa) that is known to growers in Israel as "straw bleaching," was identified and further characterized by host range, serology, electron microscopy, and molecular analysis of the nucleocapsid gene. The transmissibility of IYSV by Thrips tabaci and Frankliniella occidentalis was studied. IYSV was efficiently transmitted by T. tabaci from infected to healthy onion seedlings and leaf pieces. Two biotypes of F. occidentalis, collected from two different locations in Israel, failed to transmit the virus. Surveys to relate the incidence of thrips populations to that of IYSV were conducted in onion fields. They revealed that the onion thrips T. tabaci was the predominant thrips species, and that its incidence was strongly related to that of IYSV. Forty-five percent of the thrips population collected from IYSV-infected onion and garlic fields in Israel transmitted the virus. IYSV was not transmitted to onion seedlings from infected mother plants through the seed, and was not located in bulbs of infected plants.

The frequency of Candida parapsilosis in onychomycosis. An epidemiological survey in Israel.

Candida albicans is regarded as the major pathogen in yeast-induced onychomycosis. Based on our impression of an increasing prevalence of Candida parapsilosis in this disease, we examined the data of two mycology laboratories in the same geographic location, from 1994 to 1996 in one (centre A) and for 1995 (6 months) in the other (centre B). A total of 954 and 230 toenails and 621 and 190 fingernails, respectively, underwent KOH microscopy and culture studies in each centre. Positive findings were noted in 45 and 65% of the toenails and 44 and 72% of the fingernails, respectively. In the toenails, Candida spp. were found in 22 and 15%, respectively, and in the fingernails, in 77 and 63%, respectively. The most frequent Candida species was C. parapsilosis (39.5% in toenails, 36.7% in fingernails), followed by C. albicans (19.5% in toenails, and 34.4% in fingernails). These results demonstrate a higher frequency of isolation of C. parapsilosis compared with C. albicans in onychomycosis. This might have important therapeutic implications.

Lisianthus Leaf Necrosis: A New Disease of Lisianthus Caused by Iris yellow spot virus.

Unusual viral symptoms were seen on lisianthus (Eustoma russellianum) grown in the Besor area in Israel. Symptoms included necrotic spots and rings on leaves and systemic necrosis. Preliminary analyses suggested that the disease was caused by a tospovirus. Virus particles typical of a tospovirus were observed with electron microscopy in samples taken only from symptomatic leaves. Double-antibody sandwich enzyme-linked immunosorbent assay tests of leaf sap, extracted from lisianthus and mechanically inoculated indicator plants, gave a strong positive reaction to Iris yellow spot virus (IYSV). Polyclonal antibodies prepared against IYSV enabled specific detection of the virus in crude sap from infected plants. Western blot analysis showed that IYSV was serologically distinct from Tomato spotted wilt virus (TSWV). Primers specific to the nucleocapsid gene of IYSV were used in a reverse transcription-polymerase chain reaction assay (RT-PCR) to verify the presence of IYSV. RT-PCR gave an expected PCR product of approximately 850 bp. The sequence of the cloned nucleocapsid gene confirmed the identity of IYSV, thus confirming IYSV infection of lisianthus. This is the first report of IYSV infection in dicotyledons.

Pittosporum tobira: A New Host for Tomato spotted wilt virus.

In July 1998, Pittosporum tobira shrubs, grown in a nursery in the Sharon Valley of Israel, developed foliar ring spots, mild mosaic, and tip necrosis. Of 15 samples tested for the presence of Tomato spotted wilt virus (TSWV) with a commercially available enzyme-linked immunosorbent assay (ELISA) kit (Loewe Biochemica, Otterfing, Germany), 14 were positive for TSWV. Virus in crude sap extracted from symptomatic tissue was mechanically transmitted to Emilia spp., Petunia hybrida, Nicotiana glutinosa, N. benthamiana, and N. rustica plants, which developed symptoms characteristic of TSWV infection (1). ELISA tests of leaf sap extracted from naturally infected P. tobira and mechanically inoculated indicator plants gave a strong positive reaction to TSWV. Leaf samples of P. tobira were analyzed by transmission electron microscopy in leaf-dip preparations and thin sections of leaf tissues. Virus particles typical of a tospovirus were observed only in samples taken from symptomatic leaves. Primers specific to the nucleocapsid gene of TSWV were used in a reverse transcription-polymerase chain reaction (RT-PCR) assay to verify the presence of TSWV. RT-PCR gave an expected PCR product of ≈850 bp. The amplicon was cloned in the pGEM-T vector, and the recombinant clone was sequenced. The sequence of the cloned PCR product confirmed the identity of TSWV, verifying TSWV infection of P. tobira. This is the first report of infection of P. tobira by TSWV. Reference: (1) Y. Antignus et al. Phytoparasitica 25:319, 1997.

First Report of Impatiens Necrotic Spot Tospovirus (INSV) in Israel.

In January 1999, Anemone coronaria L. imported from Europe and grown in open fields near Jerusalem in Israel developed foliar ringspots and foliar necrosis. Within a few weeks of the first appearance of these symptoms, further anemone plants in the surrounding area were affected and seriously damaged. Impatiens necrotic spot tospovirus (INSV) was detected in affected plants by enzyme-linked immunosorbent assay (ELISA; anti-INSV monoclonal antibodies were provided by H. T. Hsu, USDA, Beltsville, MD, and a polyclonal antibody to INSV was purchased from Loewe, Otterfing, Germany). Crude sap extracted from symptomatic tissue was mechanically transmitted to Emilia spp., Petunia hybrida, Nicotian glutinosa, N. benthamiana, and N. rustica plants that developed symptoms characteristic of INSV infection (1). ELISAs of leaf sap extracted from anemone plants and mechanically inoculated indicator plants gave a strong positive reaction to INSV. Leaf-dip preparations prepared from leaf samples of anemone plants were analyzed by transmission electron microscopy (TEM). Virus particles typical of a tospovirus were observed in samples taken only from symptomatic plants. TEM studies with ultrathin sections of infected anemone and Emilia spp. leaves revealed the presence of tospovirus-like particles. This first report of INSV interception in Israel brings the count of the Tospovirus members in Israel to three, including tomato spotted wilt virus (TSWV), which was found in the past to infect anemone and other ornamental crops, and the Iris yellow spot tospovirus, infecting onion (2). INSV is known to occur in Europe and in the U.S., mostly in flowers grown in greenhouses. The virus is transmitted by the Western flower thrips (WFT; Frankliniella occidentalis Pergande). Although all infected plants were destroyed, precautions to prevent further introduction of the virus must be made. INSV might spread by the WFT, which is abundant in Israel year round, and might also infect other greenhouse or field crops. References: (1) M. Daughtrey et al. Plant Dis. 81:1220, 1997. (2) A. Gera et al. Plant Dis. 82:127, 1998.

Treatment of Candida nail infection with terbinafine.

BACKGROUND: Terbinafine is a highly potent drug against dermatophytes. Data regarding its effectiveness against Candida species are few and variable. OBJECTIVE: Our purpose was to evaluate the efficacy and safety of oral terbinafine in patients with Candida nail infection. METHODS: In an open-label uncontrolled study, 20 patients completed 16 weeks of treatment with terbinafine, 250 mg/day, and an additional 8 weeks with placebo. Efficacy was assessed clinically and mycologically at weeks 0 (baseline), 4, 8, 16, 24, 36, and 48. Routine laboratory studies were performed at baseline and weeks 4, 8, and 16. RESULTS: At the end of the trial 60% of target nails were cured clinically and mycologically; in 10% there was mycologic cure with residual clinical signs, in 25% a moderate improvement (> 50%), and failure in only 5% (one patient). Most nails were infected by Candida parapsilosis. Two of 28 patients showed mild reversible elevation of liver enzymes 1 month after initiation of terbinafine treatment. CONCLUSION: The administration of terbinafine for 16 weeks is effective in the treatment of Candida nail infection. Liver enzyme values should be determined during the first month of treatment.