First Detection of Phytoplasmas in Rhododendron in the Czech Republic.

A 10-year-old plant of rhododendron ('Cunningham's White' PS986) with leaf malformation and variegation was observed in Prague in 1997. This plant was micropropagated, and regenerants with severe, mild and no symptoms were obtained. Phytoplasma infection was detected using nested polymerase chain reaction (PCR) in the original PS986 plant and the symptomatic regenerants but not in nonsymptomatic plants. During 2002, phytoplasmas were also detected in rhododendron hybrids, PS2716 and PS2439, grown in Pruhonice that showed similar symptoms as the plant observed in Prague. In nested PCR, performed as described previously (1), primer pairs R16F1/R16R0 and R16F2/R16R2 were used. The phytoplasmas detected were classified by restriction fragment length polymorphism analysis using R16F2/R16R2 PCR fragments. Following digestion with restriction endonuclease MseI (Promega, Madison, WI), the restriction profiles obtained were identical with the pattern of the stolbur phytoplasma group (16SrXII group) as determined previously (2). To our knowledge, this is the first finding of stolbur-type phytoplasma in rhododendron worldwide. References: (1) R. Fialova et al. Plant Prot. Sci. 39(1):7, 2003. (2) I.-M Lee et al. Int. J. Syst. Bacteriol. 48:1153,1998.

Hydrocarbon deposition and soil microflora as affected by highway traffic.

The proximity of a busy highway (90,000 vehicles/day) increased the amount of polycyclic aromatic hydrocarbons (PAHs) in soil at the depth of 5-15 cm from 106 ng/g as a grassland background to 3095 ng/g dry soil at the highway verge (a sum of 10 PAH species). The PAH concentration was related to the distance from the source and exhibited a biphasic character, which is interpreted in terms of bimodal distribution of the exhaust microparticles with different rates of deposition. Similarly, the tendency of benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, and indeno(1,2,3-cd)pyrene to decrease their proportion with distance from the highway, in contrast to phenanthrene, fluoranthene, pyrene, benzo(a)pyrene, and benzo(g,h,i)perylene, was attributed to their prevalent localisation on the heavier particle fraction. The abundance of bacteria (8.33 x background) and fungi (3.17 x background) close to the highway is thought to be a consequence of hydrocarbon deposition from the traffic that serves as a significant energetic input into the soil. The elevated concentrations of hydrocarbon substrates, as indicated by PAHs, increased both the absolute and relative numbers of the microbial degraders of diesel fuel, biphenyl, naphthalene, and pyrene. Their maximum numbers at 0.5-1.5 m from the pavement reached 1.3 x 10(4), 1.2 x 10(5), 1.1 x 10(4), and 6.6 x 10(3) colony-forming units (CFU) or infection units per gramme dry soil, respectively. On the other hand, the number of anthracene degraders (1.1 x 10(3) CFU per g dry soil) remained close to the detection limit of the enumeration technique used (0.1-0.2 x 10(3) per g dry soil), consistently with the absence of anthracene and higher linear PAHs in the investigated soil samples. The amounts of persisting PAHs justify artificial inoculation with effective degrader strains in the vicinity of motorways.

First Report of Impatiens necrotic spot virus in the Czech Republic.

Impatiens necrotic spot virus (INSV) was found for the first time in the Czech Republic in 1999 in Columnea sp. and Curcuma sp. plants that were imported. They were grown in a garden among other ornamental crops. By June 2000, INSV was detected in 17 ornamental plant species in several gardening establishments never having received imported plants. Frankliniella occidentalis thrips were present at the sites of INSV infection. Natural INSV infection was found also in Stellaria media, which is an important weed species in our conditions. INSV was identified by enzyme-linked immunosorbent assay using polyclonal antibodies to INSV from Loewe Biochemica, Germany, and from Bioreba, Switzerland. The virus was transmitted in sap to Nicotiana benthamiana and Datura stramonium (1). Virus particles typical of a tospovirus were detected by electron microscopy. INSV is the second tospovirus member occurring in the Czech Republic. Tomato spotted wilt virus (TSWV) has occurred in this country since 1992 (2) and to date has been detected in more than 100 plant species including ornamentals, vegetables, and weeds. TSWV became a serious problem in glasshouse grown crops. From the epidemiological point of view the situation of INSV dissemination seems to be similar to that of TSWV. References: (1) M. Daughtrey et al. Plant Dis. 81:1220, 1997. (2) J. Mertelik and V. Mokra. Acta Virol. 42:348, 1998.

Tomato spotted wilt virus in ornamental plants, vegetables and weeds in the Czech Republic.

The occurrence of tomato spotted wilt virus (TSWV) in horticulture crops and weeds in the Czech Republic has been studied in 1992-1997. During this period TSWV was established in 91 plant species. Virus identity was based on the host range, serology and electron microscopy. Natural TSWV infection was detected in glasshouses where the main vector Frankliniella occidentalis was present too. The most frequently TSWV-infected plant species were Chrysanthemum morifolium and Zantedeschia sp. Among vegetable crops, the TSWV infection was very frequently detected in tomatoes and peppers. In all cases these plants were nursed or grown in glasshouses together with different species of ornamental plants, many of which were TSWV-infected. Among weeds, the TSWV infection occurred very often in Stellaria media and Galinsoga parviflora. These two plant species were prevalent in glasshouses and were also good hosts of F. occidentalis.