Evaluation of PCR markers for <Emphasis Type="Italic">Phytophthora infestans</Emphasis> mating type determination

Late blight is a devastating potato disease caused by Phytophthora infestans. This organism can reproduce asexually and sexually between the strains of two mating types named A1 and A2. Mating type is an important strain characteristic affecting the pathogen’s population structure. We validate different PCR markers for P. infestans mating type determination by comparison of the results obtained with the markers (W16, S1, PHYB) with the pairing test results for 26 isolates collected worldwide and for a group of 146 Polish isolates. This study identifies an interesting feature of the isolates of genotype US-1. For all these A1 mating type isolates, the product specific for A2 isolates is amplified using the marker W16. Analysis of sequences of W16 PCR products indicates high similarity of the US-1 isolates with modern A2 mating type isolates. When US-1 isolates are excluded from analysis, 95 and 96% of isolates are correctly assigned by markers W16 and S1, respectively, when compared with the pairing test results. Marker PHYB produces 14% of discrepant results with the pairing test. Our results show that molecular markers can be useful tools for P. infestans mating type determination, but their application should be preceded by validation in each local population since their efficiency may vary depending on a pathogen’s genotype.     

Recent spruce decline with biotic pathogen infestation as a result of interacting climate,deposition and soil variables

Decline or health deterioration of Norway spruce (Picea abies (L.) Karst.) dominated forest stands has recently been observed mainly in sub-mountainous parts of Central Europe. Forest inventory of 208 randomly distributed circular plots including field observations of spruce tree health and rot symptoms by honey fungus (Armillaria ostoyae) was used for assessing intensity of spruce forest health decline in a managed forest area of 12.7 th. ha located in Beskids Mts., NE Czech Republic. First, principal component analysis was used to separate inventory variables related to environmental stress (reduced apical increment, dry tree top and stem resin exudation due to A. ostoyae infestation) into PC1, and health deterioration symptoms associated with mechanical damage (peeling, crown breaks) into PC2. The first two principal components explained 59% of the total variability in health decline symptoms. Spatial variability of both principal components was explained using spatial lag regression model identified from a set of environmental variables including sulfur and nitrogen deposition, elevation, solar radiation, age of the forest stands and geological properties (geochemical reactivity index). Environmental stress (PC1) was associated with low elevations (sub-optimal for spruce), high level of nitrogen and sulfur deposition (their interaction), low geochemical reactivity and also stand age. On the other hand, mechanical damage (PC2) significantly increased with elevation and stand age. As the forest decline in Beskids Mts. is related to A. ostoyae spreading from local infestation hot spots, both principal components had a significant spatial autocorrelation, partly distorting the signal of environmental conditions. The results indicate that the disturbed forest soils by long-term acid deposition and subsequent nutrient degradation and more pronounced drought stress at low elevations are the most important drivers of the recent spruce health decline in Beskids Mts.     

Harvesting behaviour of three central European rodents: Identifying the rodent pest in cereals

In central Europe, rodent damage in cereal crops is usually attributed to the common vole but these are caused by other rodents such as Apodemus mice as well. This raises a practical problem of identifying the rodent pests causing the damage to cereals at the time of harvest. To facilitate field differentiation between the damage caused by voles or mice, we conducted laboratory experiments in which the common vole, wood mouse and pygmy field mouse were presented with standing culms of wheat. Harvesting behaviour in these rodents differed strikingly. Wood mice first climbed and then cut down the culm at a height of about 20 cm. Pygmy field mice climbed to the top of the culm, harvesting only the ear. Voles cut the culm close to the ground leaving the stubble of about 8 cm in height. Our observations provide a quick and simple clue for identifying a causal rodent species in cereals and help in adopting a proper strategy for population management of a pest rodent.     

Quantitative trait loci affecting intensity of violet flower colour in potato

Anthocyanins occur in potato tuber skin and flesh, sprouts, leaves, stems and flowers. The goal of this study was to identify genomic regions and candidate gene alleles key for accumulation of anthocyanins in potato corolla in various quantities. QTL analyses were performed in two mapping populations segregating for flower colour intensity and candidate genes were identified on the basis of function and location (chalcone isomerase, chi; chalcone synthase, chs) or location (RNA-dependent RNA polymerase 1, RDR1). We detected three and four QTL affecting the violet flower colour intensity using the two mapping populations, respectively. In both populations a locus F, necessary for violet flower colour, segregated and we used different approaches to differentiate the qualitative effect of this locus and to detect the genetic factors affecting the quantitative flower colour intensity. The strongest QTL and the only one common for the two mapping populations was located on chromosome V. The role of all three candidate genes, chi, chs and RDR1, in control of flower colour intensity is supported to different extents by the performed genetic analyses. The most important QTL on chromosome V is most likely in the same position as the QTL for anthocyanin tuber flesh coloration described previously, which indicates that the natural variation in some biosynthetic and/or regulatory genes may influence anthocyanin levels in multiple tissues.     

Professor Dr. v. Lorey

Ohne Zusammenfassung     

Root System Distribution of Highbush Blueberry Crops of Various Ages in Medium-Textured Soils

The paper deals with the spatial distribution of root density in highbush blueberry plantations of various ages for a proper planting distance recommendation and a better irrigation and fertilization management. The environmental conditions consist of sandy-loamy soils and a continental temperate climate. Two highbush blueberry cultivars were studied, ‘Bluecrop’ and ‘Blueray’. Root density (RD) and density of root cross-sectional area (RCSA) were investigated for various root diameters. It was found that the prevalent type of roots in highbush blueberry crops is the hair type, with root diameters less than 0.1?mm. Both RD and RCSA decreased with distance from plant and with soil depth; the 38-year-old crop showed a more developed root system versus the 8?year-old crop. In both cases the roots did not grow more than 0.6?m laterally and more than 0.7?m deep. According to these results, the planting distances in highbush blueberry could be reduced to substantially increase the number of plants/ha and fruit yield. Irrigation application should be carried out to wet a proper soil volume, about 0.6–0.7?m deep for older crops, and about 0.5?m deep for younger crops.     

A comparison of plotless density estimators using Monte Carlo simulation on totally enumerated field data sets

Background

Plotless density estimators are those that are based on distance measures rather than counts per unit area (quadrats or plots) to estimate the density of some usually stationary event, e.g. burrow openings, damage to plant stems, etc. These estimators typically use distance measures between events and from random points to events to derive an estimate of density. The error and bias of these estimators for the various spatial patterns found in nature have been examined using simulated populations only. In this study we investigated eight plotless density estimators to determine which were robust across a wide range of data sets from fully mapped field sites. They covered a wide range of situations including animal damage to rice and corn, nest locations, active rodent burrows and distribution of plants. Monte Carlo simulations were applied to sample the data sets, and in all cases the error of the estimate (measured as relative root mean square error) was reduced with increasing sample size. The method of calculation and ease of use in the field were also used to judge the usefulness of the estimator. Estimators were evaluated in their original published forms, although the variable area transect (VAT) and ordered distance methods have been the subjects of optimization studies.

Results

An estimator that was a compound of three basic distance estimators was found to be robust across all spatial patterns for sample sizes of 25 or greater. The same field methodology can be used either with the basic distance formula or the formula used with the Kendall-Moran estimator in which case a reduction in error may be gained for sample sizes less than 25, however, there is no improvement for larger sample sizes. The variable area transect (VAT) method performed moderately well, is easy to use in the field, and its calculations easy to undertake.

Conclusion

Plotless density estimators can provide an estimate of density in situations where it would not be practical to layout a plot or quadrat and can in many cases reduce the workload in the field.     

Some remarks on the role of vegetable plants of nutritional value in food production

Summary The influence of various factors of plants production upon the quality of vegetables was determined.Significant differences in the content of 9 mineral elements were found in 12 tested varieties of snap beans. Proper breeding can enhance the ability of accumulation of desired elements by snap bean varieties.The effect of different forms of nitrogen, phosphorus and potassium upon the carotenoid content in the carrots were examined. Nitrates were found better than urea form of nitrogen; monocalcium and tricalcium phosphates were similar in action and potassium sulphate had here greater influence than the chloride form.Experimental evidence, accumulated over a period of 3 years, is given that herbicides, recommended for particular kind of vegetables, do not decrease the nutritional values of the crop. Tomatoes, carrots, root parsley and onions were analysed for contents of dry matter, vitamin C, -carotene and total acidity.Effects of Betokson/-naphtoxy acetic acid, with a wetting agent/ and Ethrel upon the ripening of tomatoes on the vine were compared. Betokson increased more significantly the fruit set and the ripening rate of the fruits. Ethylene and Ethrel were compared in their influencing the ripening of harvested green tomatoes. Ethylene was found slighty better, but the differences were not significant.

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Zusammenfassung Es wurde der Einfluß verschiedener Anbaufaktoren auf die Qualität von Gemüsen dargelegt.Große Unterschiede im Gehalt an 9 Mineralstoffen ergaben sich in 23 analysierten Bohnensorten. Die Unterschiede an hohen erwünschten Mineralstoffgehalten sollen genetisch durch Züchtung fixiert werden.Es wurde der Einfluß von zwei Formen der Stickstoff-, Phosphor- und Kali-Verbindungen auf Gehalt von Carotinoiden in Möhren untersucht. Nitrat-Stickstoff hatte eine bessere Wirkung als Harnstoff-Stickstoff; Monocalcium-Tricalcium-Phosphate hatten einen ähnlichen Einfluß und mit Kali-Sulfat-Düngung war der Gehalt von Carotinoiden höher im Vergleich zur Düngung mit Kali-Chlorid.Dreijährige Versuchsergebnisse haben gezeigt, daß Herbizide, die zur Vernichtung von Unkraut in verschiedenen Gemüsearten empfohlen werden, den biologischen Wert der Gemüseprodukte nicht erniedrigen. Tomaten, Möhren, Wurzelpetersilie und Zwiebeln

     

Characterization of Clavibacter michiganensis subsp. michiganensis strains from recent outbreaks of bacterial wilt and canker in Serbia

Sixty-eight Clavibacter michiganensis subsp. michiganensis (Cmm) strains from recent outbreaks of bacterial wilt and canker in Serbia were collected from several tomato growing regions during a three-year period. The pathogen was identified based on bacteriological characteristics and pathogenicity tests and the identity of strains was confirmed by DAS ELISA and PCR amplification using primers CMM5/6 and PSA4/R. The strains showed homogeneity in biochemical and physiological properties. However, pathogenicity tests revealed differences in virulence that are presumably due to a loss of the pat-1 gene. Further strain characterization using DNA-based methods revealed a high diversity of the Serbian Cmm strains. Based on multi-locus sequence typing (MLST) analyses of five genes, Cmm strains were divided into seven groups. The pulsed-field gel electrophoresis (PFGE) pattern of a selection of strains supported the groupings based on trees of the kdpA/sdhA sequences. On the other hand, groupings made according to PFGE and MLST were not correlated to plasmid content in all cases. This study suggested that high genetic variability of the Serbian Cmm strains was detected both in MLST and PFGE analyses, and could have resulted either from new Cmm strains being introduced by seeds from different origins or as a consequence of an intraspecific hybridization process. In addition, this study proposed MLST as an efficient tool in epidemiological studies, population biology investigations and tracking the routes of transmission of pathogens. Four of the five house-keeping genes (kdpA, sdhA, ligA and gyrB) selected to characterize Cmm strains proved to be suitable for the MLST analysis. This is the first study carried out on the characterization of Cmm using MLST.