Pathotypes of <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis> causing damage to oilseed rape in the Czech Republic and Poland

Winter oilseed rape (Brassica napus) is an important crop in the Czech Republic and Poland. Clubroot disease caused by the pathogen Plasmodiophora brassicae is a serious and still-growing problem for oilseed rape growers in both countries. The aim of this study was to evaluate the pathotype composition of P. brassicae populations from the Czech Republic and Poland, according to the three evaluation systems, and to determine soil inoculum loads for representative fields via traditional end-point PCR as well as quantitative PCR analysis. There were considerable differences between the populations of P. brassicae from both countries, and the number of pathotypes varied depending on the evaluation system and the threshold used to distinguish susceptible vs. resistant plant reactions. This is the first study comparing the effect of different thresholds. Using an index of disease (ID) of 25 % to distinguish susceptible vs. resistant reactions, there was a total of seven pathotypes identified based on the differentials of Williams, five with the system of Somé et al., and 18 with the European Clubroot Differential (ECD) set. However, based on a threshold of 50 %, there were nine pathotypes according to the evaluation system by Williams, four based on the differentials of Somé et al., and 15 with the ECD set. Changing of the thresholds led to the reclassification of some pathotypes. Several pathotypes were common in both countries. High amounts of pathogen DNA were found in many of the field soils analysed by quantitative PCR. There was a weak correlation between soil pH and infestation of P. brassicae for the Polish soils.     

Population genetic structure of Mycosphaerella graminicola and Quinone Outside Inhibitor (QoI) resistance in the Czech Republic

Damage caused by the wheat pathogen Mycosphaerella graminicola increased rapidly during the last two decades in the Czech Republic. We collected isolates from naturally infected fields in seven wheat-growing locations and analysed these using eight microsatellite markers. All markers were highly polymorphic. We found a high degree of genetic diversity and low clonality within all sampled Czech populations. We identified 158 unique multilocus haplotypes among 184 isolates. Field populations showed weak genetic structure but we detected more differentiation between climatic regions within the Czech Republic. We compared the Czech field populations to populations from the United Kingdom, Germany and Switzerland and found a marked differentiation between Czech populations and Western European populations. We hypothesize that decades of different agricultural practices, including the use of different wheat cultivars, may explain this genetic differentiation. We detected a rapid increase in QoI fungicide resistance during the sampling period from 2005 to 2011, coinciding with the widespread application of this class of fungicides in the Czech Republic. M. graminicola populations in the Czech Republic underwent a rapid adaptive evolution from sensitivity to resistance similar to what was described earlier in Western Europe.     

Losing a staging area: Eastward redistribution of Afro-Eurasian ruffs is associated with deteriorating fuelling conditions along the western flyway

The fuelling performance of long-distance migrants at staging areas indicates local conditions and determines the viability of migration routes. Here we present a first case study where long-term fuelling performance was documented along two migration routes with differential population trends. Ruffs (Philomachus pugnax) are shorebirds of inland freshwater wetlands that migrate from the sub-Saharan wintering grounds, via Europe, to the northern Eurasian breeding grounds. Assessments from 2001 to 2008 of fuelling during northward migration at the major western and eastern staging site revealed that daily mass gain rates steeply declined across years in the grasslands for dairy production in Friesland, The Netherlands, and remained constant in the Pripyat floodplains in Belarus, 1500 km further east. Migrants in Friesland decreased from 2001 to 2010 by 66%, amounting to a loss of 21,000 individuals when counts were adjusted for length of stay as determined by resightings. In the same period numbers in Pripyat increased by 12,000. Ruffs individually ringed in Friesland were resighted in subsequent springs at increasingly eastern sites including Pripyat. Our results corroborate published evidence for an eastward redistribution of Arctic breeding ruffs and suggest that the decreasing fuelling rates in the westernmost staging area contribute to this redistribution. The shift implies that responses occur within a single generation. The hypothesis that the choice of route during northward migration may be driven by food availability can now be tested by creating greater areas of wet grasslands in Friesland. When local staging conditions improve we predict that ruffs will make the reverse shift.     

Dynamics of Atmospheric Aerosol Number Size Distributions in the Eastern Mediterranean During the ��SUB-AERO�� Project

Measurements of number size distributions of submicron aerosols have been performed at the Eastern part of Mediterranean as part of an extensive measurement campaign to study photo-oxidants and aerosols (SUB-AERO Project). The measurements were made at the Finokalia station on the island of Crete (Greece) and onboard the research vessel ??Aegaeon??. Two campaigns were performed during July 2000 and January 2001 using two scanning mobility particle sizers. The particle distributions measured in the range between 7.8 < d _p < 327 nm during the summer measurements and between 7.5 < d _p < 316 nm during the winter measurements, where d _p is the mobility particle diameter. The concentration of ultrafine particles (7.5 < d _p < 30 nm) was higher during the winter period and varied mainly between 5 × 10¹ and 2 × 10³?cm^?3 with concentration peak values for this mode exceeding 1 × 10⁴?cm^?3. During the summer campaign, an average number concentration of 1 × 10²?cm^?3 at Finokalia and about 5 × 10¹?cm^?3 aboard the ??Aegaeon?? vessel was measured. An average concentration of 1 × 10³?cm^?3 was measured for the particles in the size range between 30 and 100 nm, whereas in the size range 100?C300 nm, the measured concentration ranged between 1 × 10² and 5 × 10³?cm^?3. Diurnal patterns in number concentrations were observed in connection with the transport of air masses and local sources. During the winter period, three nucleation events were observed in connection with the appearance of a particle mode at 20 nm.     

Botanical pesticides and their human health safety on the example of Citrus sinensis essential oil and Oulema melanopus under laboratory conditions

Biopesticides derived from plants have recently received increasing interest as an alternative to conventional chemicals suitable for integrated pest management and organic farming. In this study, Citrus sinensis (Osbeck) essential oil was tested for its potential for wheat protection against Oulema melanopus (L.). The chemical composition of the essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). Twenty-four compounds were identified in the oil among which d-limonene was a predominant component, followed by myrcene, α-pinene, linalool, sabinene, decanal, and other minor components. Direct contact toxicity assay showed the effectiveness of the essential oil against O. melanopus larvae causing the mortality of 85% during 48 hours. The persistence study revealed high dissipation rate of the oil from treated plants, whereas concentrations lower than 0.01 g/kg were detected by GC-MS 5 min after the application of the oil, suggesting its environmental and food safety. These results, together with previous literature reports reviewed in this study, indicate the great potential of the C. sinensis essential oil for future use in crop protection against insect pests.     

Comparative assessment of five methods of determining sap flow in peach trees

Five different methods of determining sap flow (SF), three based on heat pulse (compensation heat pulse, New Zealand—cHP–NZ; compensation heat pulse, Greenspan/Australia—cHP–G (South oriented), and cHP–G–EW (East and West oriented, average); non-compensation heat pulse, Ariel/Israel—ncHP), one based on stem heat balance (Dynamax/USA—SHB), and another based on heat dissipation (Granier/France—HD) were compared in an experiment performed on peach trees in Northeast Spain. Two irrigation treatments (drip-irrigated) were applied: a control and a stress treatment, the latter consisting of withholding water from day 190 to 199. Between 1 and 3 different systems were installed in some trees of both, the control and stress treatments. All the techniques reflected the evolution of water stress in the stressed trees with a very similar tendency and in agreement with the evolution of predawn water potential (Ψp). Ψp correlated well with sap flow (SF) determined with all the systems (r² > 0.65) in the stress treatment, indicating that all the SF techniques detected changes in tree water status. The cHP–NZ system was the first to detect a SF reduction through the outer xylem vessels, as a response to water withholding. In control trees, daily SF rates provided by the three heat pulse and heat balance methods were well correlated with ETo and somewhat less with global radiation; all regressions improved on an hourly basis. Daily pattern and magnitude of mean SF rates monitored by the three heat pulse systems were quite similar in control trees. This was reflected by high regression coefficients when compared with each other. Higher SF rates recorded by ncHP methods in comparison with cHP–G and cHP–NZ might be attributed to technical limitations and to different sensor orientation. In an accompanying experiment, substantial differences between East and West location of the cHP–G sensors were observed, but when taking the mean value of those daily SF rates, differences between ncHP and cHP–G–EW were lower. Mean monthly crop coefficients, calculated by using SF data computed with ncHP method and soil evaporation as determined with microlysimeters, were 0.64 in July and 0.67 in August. SF systems can be used to detect plant water stress related to control, and might be useful for irrigation scheduling based on plant water status. The SF techniques analysed showed potential to better determine actual plant water necessities than other traditional methods, but a preceding calibration is needed.     

A rapid real-time PCR assay for detecting columnar growth in apples (Malus × domestica)

Columnar growth in apples can have considerable positive consequences for orchard maintenance, but the lack of columnar cultivars producing fruits with desired market quality prevents their broader utilization in orchards. New crossings focused on their breeding are therefore conducted throughout the world every year. Unfortunately, the reliable discrimination between columnar growth and normal phenotype is difficult until seedlings are 2–3 years of age. However, molecular marker–assisted selection (MAS) can be used in seedlings several weeks old providing immense help in breeding programmes focused on columnar apple production. Here, we describe a rapid and reliable method for the detection of both wild-type (WT) and columnar (Co) alleles originating from ‘McIntosh Wijcik’ in a single reaction using a real-time PCR allelic discrimination approach. Our assay was tested in 130 genotypes (80 normal and 50 columnar habit) from various crossings and their parents, and in all cases, genotype corresponded to phenotype. The assay is thus suitable for laboratories interested in high-throughput MAS for columnar tree habit breeding.