The infection of potatoes byPhytophthora infestans during simulated washing and its control using a hot water treatment

Summary A single blighted tuber released on average 1.39 mg ofP. infestans mycelia and sporangia during simulated washing. In subsequent experiments up to 100% of tubers were infected when healthy tubers were washed in a suspension ofP. infestans equivalent to a concentration of 1.65 μg ml⁻¹, i.e. that calculated to be in a commercial washing plant after washing a potato stock with approximately 1% of tubers infected with blight for 4 hours. Immature tubers were more prone to infection during washing than mature tubers. Damaging tubers, irrespective of their maturity, increased the incidence of tuber infection. The viability ofP. infestans isolates was significantly reduced byin vitro immersion in water at 44°C for 5 minutes. The infection of daughter tubers dipped in a suspension ofP. infestans for 3 minutes was prevented when the suspension temperature was 44°C. There was no indication of tuber damage at this temperature.     

Epidemiology of parasitic gastrointestinal nematode infections of ruminants on smallholder farms in central Kenya

In order to establish the infection pattern with gastrointestinal nematodes in ruminants in the central Kenya highlands, a study was carried out in 58 smallholder farms. The study involved monthly faecal examinations from sheep, goats and cattle and pasture sampling from eight communal grazing areas. Each month, six Dorper worm-free tracer lambs were introduced and four locally grazed cross-bred sheep were purchased for parasite recovery. The mean faecal egg counts (FEC) for cattle were low throughout the study period, whereas those for sheep and goats showed a seasonal pattern with high levels of infection occurring during the two main rainy seasons, especially in March, April and October. There were significant differences in egg counts over time and among farms. Haemonchus contortus was the most prevalent nematode in the tracer lambs whereas the previously exposed locally grazed sheep had significantly lower numbers of H contortus but significantly higher numbers of Trichostrongylus species The highest levels of infection in the tracer lambs occurred in November 1995 and January, May and June 1996. Based on this study, it is now possible to explore the possibility of using strategic treatments for the control of parasitic gastroenteritis in this area of Kenya.     

免疫失败兔群一株支气管败血波氏杆菌免疫原性及致病性初探

采用微量凝集试验（ＭＡＴ）〔１～３〕法,对免疫失败兔群分离的兔支气管败血波氏杆菌分离菌株（Ｂｒ－Ｓ９５）与本室保存的参考菌株（Ｓ８０１０３）制备的疫苗的免疫效果作了检测,比较结果表明,兔支气管败血波氏杆菌Ｂｒ－Ｓ９５菌株与本室保存的Ｓ８０１０３菌株制苗免疫后的抗体水平在各自高峰期差异不显著（Ｐ＞０．０５）。交叉免疫试验表明,分离菌株免疫的抗体水平在１∶２８．８７时,对Ｓ８０１０３菌株的攻毒具有保护力,而Ｓ８０１０３菌株免疫后的抗体水平达到１∶２９．６７时仍不能抵抗分离菌株的攻毒,因此分离菌株是一株毒力较强的支气管败血波氏杆菌。     

Integrated control of potato late blight: predicting the combined efficacy of host resistance and fungicides

Integrating cultivars that are partially resistant with reduced fungicide doses offers growers an opportunity to decrease fungicide input but still maintain disease control. To use integrated control strategies in practice requires a method to determine the combined effectiveness of particular cultivar and fungicide dose combinations. Simple models, such as additive dose models (ADM) and multiplicative survival models (MSM), have been used previously to determine the joint action of two or more pesticides. This study tests whether a model based on multiplicative survival principles can predict the joint action of fungicide doses combined with cultivars of differing partial host resistance. Data from eight field experiments on potato late blight (Phytophthora infestans) were used to test the model; the severity of foliar blight was assessed and scores used to calculate the area under the disease progress curve (AUDPC). A subset of data, derived from the most susceptible cultivar, King Edward, was used to produce dose–response curves from which parameter values were estimated, quantifying fungicide efficacy. These values, along with the untreated values for the more resistant cultivars, Cara and Sarpo Mira, were used to predict the combined efficacy of the remaining cultivar by fungicide dose combinations. Predicted efficacy was compared against observations from an independent subset of treatments from the field experiments. The analysis demonstrated that multiplicative survival principles can be applied to describe the joint efficacy of host resistance and fungicide dose combinations.     

Plasma adrenocorticotropin, cortisol, and adrenocorticotropin/cortisol ratios in septic and normal-term foals

BACKGROUND: Little information exists on the hypothalamic-pituitary-adrenal axis in septic foals. HYPOTHESIS: The plasma concentrations of adrenocorticotropin (ACTH) and cortisol are expected to be higher in septic foals as compared to normal foals. The concentrations of hormones in septic foals also are expected to differ further depending upon survival. ANIMALS: Twenty-eight control foals and 46 septic foals <14 days of age were included in this study. METHODS: Blood was collected in EDTA once from 28 normal foals born in the University of Georgia or Cornell University equine research herds and from 46 septic foals within 12 hours after admission to 1 of the 3 tertiary care referral centers involved in the study. Septic foal selection was based on a sepsis score of >11 or a positive blood culture. The control foals were age matched to the septic foals in the study. ACTH and cortisol concentrations were measured by a chemiluminescent immunoassay system. RESULTS: Cortisol concentrations in control foals did not vary with age. Septic foals had significantly higher mean ACTH, cortisol, and ACTH/cortisol ratios than did normal foals. Within the septic foal group, 28 foals survived to discharge, and 18 were euthanized or died. The mean age was not significantly different between the septic surviving and nonsurviving foals. The mean ACTH/cortisol ratio was significantly higher in the septic nonsurviving foals as compared to the septic surviving foals. CONCLUSIONS AND CLINICAL IMPORTANCE: Septic foals had higher hormone concentrations as compared to normal foals, which is an expected endocrine response to critical illness. The increased ACTH/cortisol ratio in nonsurviving septic foals in comparison to surviving septic foals could indicate hypothalamic-pituitary-adrenal axis dysfunction at the level of the adrenal gland in critically ill septic foals.     

Placing the pieces: Reconstructing the original property mosaic in a warrant and patent watershed

Recent research shows that land use history is an important determinant of current ecosystem function. In the United States, characterization of land use change following European settlement requires reconstruction of the original property mosaic. However, this task is difficult in unsystematically surveyed areas east of the Appalachian Mountains. The Gwynns Falls watershed (Baltimore, MD) was originally surveyed in the 1600-1700s under a system of warrants and patents (commonly known as ‘metes and bounds’). A method for the reconstruction and mapping of warrant and patent properties is presented and used to map the original property mosaic in the Gwynns Falls watershed. Using the mapped mosaic, the persistence of properties and property lines in the current Gwynns Falls landscape is considered. The results of this research indicate that as in agricultural areas, the original property lines in the Gwynns Falls watershed are persistent. At the same time, the results suggest that the property mosaic in heavily urbanized/suburbanized areas is generally ‘reset.’ Further, trends in surveying technique, parcel size, and settlement patterns cause property line density and property shape complexity to increase in the less urbanized upper watershed. The persistence of original patterns may be damping expression of heterogeneity gradients in this urban landscape. This spatial pattern of complexity in the original mosaic is directly opposite of hypothesized patterns of landscape heterogeneity arising from urbanization. The technique reported here and the resulting observations are important for landscape pattern studies in areas settled under unsystematic survey systems, especially the heavily urbanized areas of the eastern United States. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photo-induced changes in the concentrations of individual chlorogenic acid isomers in potato (Solanum tuberosum) tubers and their complexation with ferric ions

Summary Changes in the concentrations of 3-, 4- and 5-caffeoylquinic acids in potato tubers exposed to light have been determined by high-performance liquid chromatography. In the first 24 to 48 hours the observed increases in total chlorogenic acid content was due primarily to an increase in 5-caffeoylquinic acid content but thereafter the rate of accumulation of the other isomers increased gradually. After 24 hours exposure 4-caffeoylquinic acid accounted for 10% of the total chlorogenic acid content of the tubers compared with 33% after 168 hours. The significance of this change in isomeric ratio on the spectral characteristics of potential ferrichlorogenic acid complexes was investigated in vitro. It was concluded that potato quality, as reflected in the development of after-cooking blackening, was dependent on total chlorogenic acid content and was unaffected by the relative concentrations of the individual isomers.