Comparison of the specificty of human and bovine tuberculin PPD for testing cattle. 1--Republic of Ireland.

A tuberculin testing trial in cattle was carried out in the Republic of Ireland to compare the specificity for bovine tuberculosis of a human purified protein derivative (PPD) tuberculin (Weybridge) with that of a bovine PPD (Rotterdam), and to determine whether discrimination between specific and non-specific reactions to mammalian tuberculin is better with doses of tuberculins smaller than those traditonally used for testing cattle. Tests were carried out in 510 cattle, 395 of which were shown by post mortem examination to be tuberculous and 115 non-tuberculous. Three dilutions at five-fold intervals of both mammalian tuberculins were used together with two dose levels of avian tuberculin PPD (Weybridge), and all reactions were measured both by increase in skin fold thickness and by diameter of induration. In the environment of this trial, the bovine PPD was shown to be more specific for bovine tuberculosis than the human PPD, and particularly in differentiating from "skin tuberculosis". There was no indication of greater specificity at lower doses of tuberculin. Measurement of induration diameter proved a satisfactory alternative method of reading tuberculin reactions in cattle under field conditions.     

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.     

Beschreibung des Feuerbrandbefalls am Institut für Obstzüchtung in Dresden-Pillnitz im Jahr 2003

The orchard of the Institute of Fruit Breeding of the German Federal Centre of Breeding Research on Cultivated Plants in Dresden-Pillnitz was highly affected by fire blight in 2003. Infected pomefruit trees were observed over a period of nearly 3 months. The first symptoms on pear trees were found on May 19th. The pathogen Erwinia amylovora was confirmed officially on May 26, and the last infected apple trees were detected the 11th of August. The infected trees had to be grubbed at the decision of the Phytopathological Authority. In total, 1164 apple and 478 pear trees were grubbed, including the entire pear collection of the gene bank. Of 35 wild species of pear, 49 accessions, eight accessions of six species each, showed infections. The apple collection of the gene bank included 33 wild species, with 365 accessions, and 845 cultivars and clones. Ten accessions of nine wild apple species and 81 cultivars/clones of these collections showed fire blight infection. The source of infection was the pear collection, and the distance from that source was important for the occurrence of infection. Field plots close to the pear collection had tree losses of 10–34%, while more distant plots had losses of 0–6%. Around 80% of the lost apple trees were detected and grubbed from 27th May to 11th June. Some of the cultivars bred in Dresden-Pillnitz, e.g. ‘Pilot’ and ‘Rekarda’, were affected by fire blight in most field plots, whereas most others were affected mainly only in plots adjacent to the infection source. A correlation of r=?0.72 could be calculated for rating in artificial shoot inoculations and percentage of trees of resistant cultivars lost. The cultivars ‘Pirol’, ‘Reanda’, ‘Remo’, ‘Rene’, ‘Renora’, ‘Resi’, and ‘Retina’ showed only a very low numbers of infected trees. No tree of ‘Rewena’ showed symptoms of fire blight. Despite a tendency to postblooming, only 8.9% of ‘Pinova’ trees had to be grubbed.