鸡传染性鼻炎流行病学调查（Ⅱ）

利用鸡传染性鼻炎PCR试剂盒和阻断ELISA试剂盒，对29份菌株、136份临床样品和1019份血清进行了检验和分析，结果PCR阳性率为36.4%，A型阳性率为10.3%，C型阳性率为6.4%。     

Hydroxycinnamic acid ethyl esters as precursors to ethylphenols in wine

A method for determining ethyl coumarate and ethyl ferulate in wine using GC-MS with deuterium-labeled analogues has been developed and used to measure the evolution of these two esters during the production of two commercial monovarietal red wines, cv. Grenache and Shiraz. During fermentation, the concentration of ethyl coumarate rose from low levels to 0.4 mg/L in Grenache and 1.6 mg/L in Shiraz wines. These concentrations then increased further during barrel aging to 1.4 and 3.6 mg/L, respectively. The concentration of ethyl ferulate was much lower, reaching a maximum of only 0.09 mg/L. Conversion of ethyl coumarate and ethyl ferulate to their corresponding ethylphenols was observed during fermentations of a synthetic medium with two strains of Dekkera bruxellensis (AWRI 1499 and AWRI 1608), while a third (strain AWRI 1613) produced no ethylphenols at all from these precursors. Strains AWRI 1499 and 1608 produced 4-ethylphenol from ethyl coumarate in 68% and 57% yields, respectively. The corresponding yields of 4-ethylguaiacol from ethyl ferulate were much lower, 7% and 3%. Monitoring of ethyl coumarate and ethyl ferulate concentration during the Dekkera fermentations showed that the selectivity for ethylphenol production according to yeast strain and the precursor was principally a result of variation in esterase activity. Consequently, ethyl coumarate can be considered to be a significant precursor to 4-ethylphenol in wines affected by these two strains of Brettanomyces/Dekkera yeast, while ethyl ferulate is not an important precursor to 4-ethylguaiacol.     

Root infection of potato by Spongospora subterranea: knowledge review and evidence for decreased plant productivity

Information is reviewed on root infection of potato by the plasmodiophorid Spongospora subterranea f. sp. subterranea. This pathogen has long been recognized as the cause of root galls (hyperplasia) and the economically important disease powdery scab on tubers (modified stolons). The significance for plant productivity of the zoosporangium stages of the pathogen in potato roots has only recently begun to be documented. Two experiments are described that assessed effects of S. subterranea root infection on potato plant root function and productivity. A greenhouse experiment measured root function and plant parameters for eight potato cultivars with markedly different susceptibilities to tuber powdery scab. Water uptake and plant growth were reduced by S. subterranea inoculation in all eight cultivars. The magnitudes of these negative effects, and intensities of root hyperplasia, differed among the cultivars, but were not related to respective susceptibilities to tuber powdery scab. A field trial assessed root function and plant productivity for a cultivar (Iwa) that is very susceptible to Spongospora tuber and root diseases. Soil water content beneath uninoculated plants was consistently less than for inoculated plants, indicating that inoculation reduced water uptake (root function). Inoculation reduced shoot and root dry weights, and reduced weight of tubers per plant by 42%. Spongospora subterranea causes three diseases of potato: root membrane dysfunction, root hyperplasia and tuber powdery scab. The root diseases caused by the pathogen are likely to be important both for powdery scab management and for deleterious effects on potato crop yields.     

Origin of the pH-dependent cation exchange capacities of Irish soil clays

Values of cation exchange capacity determined at pH 4.8 and at pH 8.2 are reported for peroxidized clay separates from a group of Irish soils derived from a variety of parent materials. The correlation between the two measurements was poor. The differences between the values (pH-dependent CEC's) ranged from 0.1 to 58.6 mequiv./100 g, with a mean of 12.9 mequiv./100 g. The highest values were associated with clays from spodic horizons and clays from basalt-derived soils. CEC at pH 8.2 and pH-dependent CEC were highly correlated with citrate-dithionite-bicarbonate (CDB) extractable Al. In contrast, CEC at pH 4.8 was negatively correlated with this parameter, suggesting that hydrous oxides reduced CEC at low pH values.Values of CEC of pH 4.8 and pH 8.2 are also reported for a selection of 16 clays subjected to sequential extraction with CDB and NaOH. CDB treatment reduced mean pH-dependent CEC from 20.4 to 9.0 mequiv./100 g, which was reduced to 3.9 mequiv./100 g by subsequent extraction with NaCH. The material removed by CDB was apparently positively charged at pH 4.8 and negatively charged at pH 8.2. Most of the pH-dependent CEC remaining after CDB treatment was associated with the clays from spodic horizons. The material extracted by NaOH was apparently negatively charged at both pH 4.8 and pH 8.2. No direct evidence of the physical nature of this material was obtained but it was present in sufficient amounts to suggest that it existed in particular forms in some of the clays from the spodic horizons. Following the dissolution treatments, the correlation between CEC values at pH 4.8 and pH 8.2 was very good (r = 0.99).