Microbiology of normal and seborrheic canine skin.

Quantitative and qualitative bacterial assays were performed on the skin of 15 normal and 32 seborrheic dogs. Nonionic detergent scrubs were made on areas demarcated by glass sidearm cylinders. Quantitative analysis was accomplished by the serial dilution technique, and the bacteria were identified by individual and colonial morphology and by enzyme production. Areas measured on control dogs had a markedly lower total bacterial count than similar areas measured on seborrheic animals. Control dogs had a flora consisting primarily of coagulase-negative cocci, whereas seborrheic dogs usually had a cutaneous flora composed primarily of Stahylococcus aureus, coagulase-positive.     

The effects of ultraviolet-B (UV-B: 290–320 nm) radiation on blister blight disease of tea (Camellia sinensis)

Sunlight is known to reduce the incidence of blister blight disease of tea, caused by Exobasidium vexans . The effects of the ultraviolet-B (UV-B: 290–320 nm) component of solar radiation on the disease and the development of E. vexans were studied in the field in Sri Lanka using UV-screening filter materials held over a commercial crop. Exclusion of UV-B radiation by Polyester, which reduces fluxes in the UV-B region by approximately 75–85%, increased both the number of translucent spots (immature sites of infection) and number of sporulating blisters (mature sites of infection), but it had little or no effect on the sporulation of the pathogen. When basidiospores were artificially inoculated on leaves, and were exposed to full or filtered solar radiation, their survival and germination increased when UV-B wavelengths were removed; significant differences were found 62 h after inoculation. However, UV-B did not affect the extension of germ tubes. This study indicates that the UV-B component of solar radiation plays an important role in the natural regulation of blister blight disease in the field.     

Development of a powder formulation of Pseudomonas fluorescens for control of rice blast

Pseudomonas fluorescens strain Pf1, inhibitory to the growth of the rice blast pathogen Pyricularia oryzae in vitro , was developed as a talc-based powder formulation. When rice seeds were treated with this formulation, the bacteria spread to roots, stems and leaves of the plants and protected against leaf infection by P. oryzae . When applied as a foliar spray, the bacteria survived on the leaves. The powder formulation controlled leaf blast under greenhouse conditions. In tests as a seed treatment and foliar spray in four field trials it effectively controlled the disease and increased grain yield.     

Weed communities of winter wheat as influenced by input level and rotation

The influence of cropping systems constituted by the combination of three input levels (low, intermediate and high) and four 2-year rotations between a spring summer crop and winter wheat ( Triticum aestivum L.) on the density and composition of the winter wheat weed flora was evaluated from 1989 to 1992. Spring summer crops were maize ( Zea mays L.). soyabean ( Glycine max (L.) Merr.). sugar beet ( Beta vulgaris L.) and sunflower ( Helianthus and L.) Total weed density at the end of the wheat tillering stage ranged from 2.5 to 128.7 plants m^-2 and generally decreased with cropping intensity, although to a differing extent, depending upon rotation. Differences among weed communities of the 12 cropping systems were mostly dependent upon input level. The effect of the preceding crop on the weed flora composition of winter wheat was evident only with reduced herbicide use (low-input systems). Weed species could be ascribed to four categories: (a) species sporadically associated with cropping systems (most of the weeds); (b) species associated with a specific input level (e.g. Papaver rhoeas L. to low and intermediate input levels and Veronica persica Poiret to the high input ievel): (c) species associated with a specific rotation (e.g. Anm majus L. to sugar beet winter wheat): and (d) species associated with specitie plots that become important every other year (e.g. Convolvulus arvensis L. and Stellaria media (L.) Vill.).     

Changes in the content of steroidal glycoalkaloids in potato tubers grown in the field and in the greenhouse under different conditions of light, temperature and daylength

Differences in the content of steroid glycoalkaloids (SGA) were noted in the peels of potato tubers cultivars Alpha, Cara, Désirée and LT-7. Cultivar LT-7 had always the highest SGA content, Désirée was intermediate and Alpha and Cara had the lowest SGA content, regardless of growing conditions, tuber ageing and tuber treatments. Tubers grown during the summer developed the highest SGA content as compared to those grown in the spring and winter seasons, respectively. Tubers grown during winter showed an increase in SGA toward the end of the storage period. Similar results were obtained with tubers of LT-7 grown in a greenhouse under cool temperatures in combination with short days (which imitate the winter conditions in Israel). A decrease in SGA content was observed in tuber slices treated with a fungal cell-wall preparation fromPhytophthora citrophthora. This decrease was much stronger in the pith than in the peel, indicating a possible role for SGA in the defence mechanism because peels are the first part of the tuber to be invaded by pathogens. The above results were observed in tubers of all cultivars regardless of the growing season or tuber ageing.     

Biology of a new virus isolated from Lupinus nootkatensis plants in Alaska

A new virus named Nootka lupine vein-clearing virus (NLVCV) was isolated from Lupinus nootkatensis plants that were confined to a relatively small area in the Talkeetna mountains of south-central Alaska. Annual surveys (2000–03) consistently found leaf symptoms of pronounced vein clearing and mosaic on 3- to 4-week-old plants in late June. Spherical particles ≈30 nm in diameter were isolated from these leaves. Virions contained a single-stranded RNA of ≈4·0–4·2 kb and one species of capsid protein estimated to be ≈40 kDa. The double-stranded RNA profile from naturally infected leaves consisted of three major bands ≈4·2, 1·9 and 1·5 kbp. Protein extractions from either sap or virions of diseased plants reacted to polyclonal antiserum made against the virions in Western blot assays. A predicted PCR product ≈500 bp was synthesized from virion RNA using primers specific to the carmovirus RNA-dependent RNA polymerase (RDRP) gene. The nucleotide sequence of the amplified DNA did not match any known virus, but contained short regions of identity to several carmoviruses. Only species belonging to the Fabaceae were susceptible to NLVCV by mechanical inoculation. Based on dsRNA profile, size of virion RNA genome and capsid protein, and similarity of the RDRP gene to that of other carmoviruses, it is suggested that NLVCV is a member of the family Tombusviridae , and tentatively of the genus Carmovirus . As the host range, RDRP gene and dsRNA profile of NLVCV are different from those of known viruses, this is a newly described plant virus.