Impact of Stolbur Phytoplasmas on Potato Tuber Texture and Sugar Content of Selected Potato Cultivars

Potato stolbur is a phytoplasmal disease that seriously affects yield and tuber quality in South Eastern Europe, Russia and the Mediterranean areas. In 2007 and 2008, field experiments were carried out to determine stolbur resistance of processing potato cultivars at Sannicolau Mare (Romania) by determining consistency and concentration of reducing sugars (fructose and glucose), sucrose and phytoplasmas in potato tubers. In both years, non-symptomatic potato tubers showed sucrose levels in the range of 3,000 mg kg⁻¹ fresh weight (FW). In contrast, sucrose concentrations were up to 11,820 mg kg⁻¹ FW in 2007 and 19,560 mg kg⁻¹ FW in 2008 in tubers showing severe symptoms. These high values severely affect suitability of tubers for processing as sucrose serves as substrate for the formation of reducing sugars that are the limiting factor in fried potato production for Maillard-related discolouration. The cultivars examined differed considerably in susceptibility to stolbur disease. Whereas cvs. ‘Courage’ and ‘Lady Rosetta’ showed high numbers of diseased tubers and high sucrose concentrations, ‘Lady Claire’ had a lower incidence of symptomatic tubers and lower sucrose concentrations. However, fully resistant cultivars were not observed. Across all cultivars examined, phytoplasmal concentration was significantly higher in symptomatic tubers than in non-symptomatic ones.     

Local response of bacterial densities and enzyme activities to elevated atmospheric CO2 and different N supply in the rhizosphere of Phaseolus vulgaris L.

Altered flux of labile C from plant roots into soil is thought to influence growth and maintenance of microbial communities under elevated atmospheric CO₂ concentrations. We studied the abundance and function of the soil microbial community at two levels of spatial resolution to assess the response of microorganisms in the rhizosphere of the whole root system and of apical root zones of Phaseolus vulgaris L. to elevated CO₂ and high or low N supply.

At the coarser resolution, microbial biomass C, basal respiration and phospholipid fatty acid (PLFA) patterns in the rhizosphere remained unaffected by elevated CO₂, because the C flux from the whole root system into soil did not change [as shown by Haase, S., Neumann, G., Kania, A., Kuzyakov, Y., Römheld, V., Kandeler, E., 2007. Elevation of atmospheric CO₂ and N-nutritional status modify nodulation, nodule carbon supply, and root exudation of Phaseolus vulgaris L. Soil Biology & Biochemistry 39, 2208–2221]. At a higher spatial resolution, more low-molecular-weight compounds were released from apical root zones under elevated CO₂. Thus, at an early stage of plant growth (12 days after sowing), elevated CO₂ induced an increase of enzyme activities (xylosidase, cellobiosidase and leucine-aminopeptidase) in the rhizosphere soil of apical root zones. At later stages of plant growth (21 days after sowing), however, enzyme activities (those above as well as N-acetyl-β-glucosaminidase and phosphatase) decreased under elevated CO₂. The abundance of total and denitrifying bacteria in the rhizosphere soil of apical root zones was unaffected by CO₂ elevation or N supply. Plant age seemed to be the main factor influencing the density of the bacterial community. In conclusion, the soil microbial community in the apical root zone responded to elevated CO₂ by altered enzyme regulation (production and/or activity) and not by greater bacterial abundance.     

Non-invasive imaging of plant roots in different soils using magnetic resonance imaging (MRI)

Background

Root systems are highly plastic and adapt according to their soil environment. Studying the particular influence of soils on root development necessitates the adaptation and evaluation of imaging methods for multiple substrates. Non-invasive 3D root images in soil can be obtained using magnetic resonance imaging (MRI). Not all substrates, however, are suitable for MRI. Using barley as a model plant we investigated the achievable image quality and the suitability for root phenotyping of six commercially available natural soil substrates of commonly occurring soil textures. The results are compared with two artificially composed substrates previously documented for MRI root imaging.

Results

In five out of the eight tested substrates, barley lateral roots with diameters below 300 µm could still be resolved. In two other soils, only the thicker barley seminal roots were detectable. For these two substrates the minimal detectable root diameter was between 400 and 500 µm. Only one soil did not allow imaging of the roots with MRI. In the artificially composed substrates, soil moisture above 70% of the maximal water holding capacity (WHC_max) impeded root imaging. For the natural soil substrates, soil moisture had no effect on MRI root image quality in the investigated range of 50–80% WHC_max.

Conclusions

Almost all tested natural soil substrates allowed for root imaging using MRI. Half of these substrates resulted in root images comparable to our current lab standard substrate, allowing root detection down to a diameter of 300 µm. These soils were used as supplied by the vendor and, in particular, removal of ferromagnetic particles was not necessary. With the characterization of different soils, investigations such as trait stability across substrates are now possible using noninvasive MRI.

     

Anaerobic bacterial infections causing osteomyelitis/arthritis in a dog.

A 3-year-old German Shepherd Dog was examined for lameness, signs of pain, swelling, a draining fistulous tract, and osteolysis after a dog bite on the left carpus. After failure of the lesion to respond to several antibiotics, Peptostreptococcus sp and Propionibacterium sp were isolated from swab specimens and then from surgically collected bone and soft tissue specimens. The bone fragments had mild purulent osteomyelitis associated with numerous gram-positive rods and cocci. The dog was successfully treated by surgical debridement of the lesion and clindamycin administration.     

Age-period-cohort analysis of the Bovine Spongiform Encephalopathy (BSE) epidemic in Switzerland

Cattle born after animal-feed control measures were implemented in 1990 have become BSE cases in Switzerland, indicating sub-optimal effectiveness of these measures. To evaluate these measures, the incidence of BSE cases in Switzerland recorded through clinical case reporting from January 1991 to June 2000 (categorized into age groups and birth cohorts of 6-month duration) was analyzed by Poisson log-linear regression using an age–period–cohort model. The incidence was maximum in the cattle cohort born from October 1989 to March 1990, and dropped to zero in the cohort born from April to September 1991. A second peak was observed in a cohort born from April to September 1994. The first drop of incidence is interpreted as a result of initial implementation of the feed ban in 1990. The second peak might be related to exposure of cattle to feed intended for pigs and poultry.     

Neuropathological survey of fallen stock: active surveillance reveals high prevalence of encephalitic listeriosis in small ruminants

This paper describes the prevalence of brain lesions in the Swiss fallen stock population of small ruminants. 3075 whole brains (75% sheep, 25% goats) were collected as part of a year-long active survey of transmissible spongiform encephalopathies (TSEs) in small ruminants conducted by the Swiss authorities between July 2004 and July 2005. All fallen stock brains were systematically examined by histopathology to obtain reliable data on histologically identifiable brain lesions. Lesions were found in an unexpectedly high number of animals (8.1% of all examined brains). A wide spectrum of diseases was detected showing that this approach provides an excellent opportunity to screen for the prevalence of neurological diseases. Encephalitic listeriosis was by far the most frequent cause of CNS lesions in both species and its prevalence was unexpectedly high when compared to notified confirmed cases. In conclusion, the prevalence of listeriosis as estimated by passive surveillance based on the notification of clinical suspects has been underestimated in the past.     

Healthy Aspects of Potatoes as Part of the Human Diet

Potatoes are constituents of many diets. Nutritionalists identify several positive aspects but also discuss some adverse reactions. Therefore, healthiness of potato food has to be established taking into account new knowledge about natural constituents and food-borne substances. This paper presents data of three main areas: carbohydrates, toxins and antioxidants. The glycaemic behaviour of prepared potatoes has discredited the general understanding of potatoes as a healthy foodstuff. Boiled or steamed potatoes contain a large amount of rapidly available starch, but alongside genotype driven variability some preparation steps may also have an influence. The glycaemic load as the most relevant criterion for healthy subjects is relatively low. Potatoes may contain toxins, either natural (e.g. glycoalkaloids) or food-borne toxins (e.g. acrylamide). Minimization strategies have been developed for several potato dishes to reduce the intake substantially. Consumer handling particularly determines the specific level with those toxins. Antioxidants are a potent source of health promoting reactions in humans. They are present in potatoes, but specific concentrations are related to several aspects, e.g. plant growth, time interval after lifting, genotype, and kind of preparation. Again, the way in which consumers handle the potatoes is relevant. In summary, potatoes are very well suited for our modern diet, but consumers need advice to ensure that they are stored and prepared in the most appropriate way.     

Ecosystem service supply and vulnerability to global change in Europe

Global change will alter the supply of ecosystem services that are vital for human well-being. To investigate ecosystem service supply during the 21st century, we used a range of ecosystem models and scenarios of climate and land-use change to conduct a Europe-wide assessment. Large changes in climate and land use typically resulted in large changes in ecosystem service supply. Some of these trends may be positive (for example, increases in forest area and productivity) or offer opportunities (for example, "surplus land" for agricultural extensification and bioenergy production). However, many changes increase vulnerability as a result of a decreasing supply of ecosystem services (for example, declining soil fertility, declining water availability, increasing risk of forest fires), especially in the Mediterranean and mountain regions.