Beschreibung des Feuerbrandbefalls am Institut für Obstzüchtung in Dresden-Pillnitz im Jahr 2003

The orchard of the Institute of Fruit Breeding of the German Federal Centre of Breeding Research on Cultivated Plants in Dresden-Pillnitz was highly affected by fire blight in 2003. Infected pomefruit trees were observed over a period of nearly 3 months. The first symptoms on pear trees were found on May 19th. The pathogen Erwinia amylovora was confirmed officially on May 26, and the last infected apple trees were detected the 11th of August. The infected trees had to be grubbed at the decision of the Phytopathological Authority. In total, 1164 apple and 478 pear trees were grubbed, including the entire pear collection of the gene bank. Of 35 wild species of pear, 49 accessions, eight accessions of six species each, showed infections. The apple collection of the gene bank included 33 wild species, with 365 accessions, and 845 cultivars and clones. Ten accessions of nine wild apple species and 81 cultivars/clones of these collections showed fire blight infection. The source of infection was the pear collection, and the distance from that source was important for the occurrence of infection. Field plots close to the pear collection had tree losses of 10–34%, while more distant plots had losses of 0–6%. Around 80% of the lost apple trees were detected and grubbed from 27th May to 11th June. Some of the cultivars bred in Dresden-Pillnitz, e.g. ‘Pilot’ and ‘Rekarda’, were affected by fire blight in most field plots, whereas most others were affected mainly only in plots adjacent to the infection source. A correlation of r=?0.72 could be calculated for rating in artificial shoot inoculations and percentage of trees of resistant cultivars lost. The cultivars ‘Pirol’, ‘Reanda’, ‘Remo’, ‘Rene’, ‘Renora’, ‘Resi’, and ‘Retina’ showed only a very low numbers of infected trees. No tree of ‘Rewena’ showed symptoms of fire blight. Despite a tendency to postblooming, only 8.9% of ‘Pinova’ trees had to be grubbed.     

Potential of Borago officinalis, Sinapis alba L. and Phacelia boratus for Phytoextraction of Cd and Pb from Soil

Heavy metal phytoextraction is a soil remediation technique, which makes use of plants in removing contamination from soil. The plants must thus be tolerant to heavy metals, adaptable to soil and climate characteristics, and able to take up large amounts of heavy metals. Most of the high biomass productive plants such as, maize, oat and sunflower are plants, which do not grow in cold climates or need intensive care. In this study three “weed” plants, Borago officinalis; Sinapis alba L. and Phacelia boratus were investigated for their ability to tolerate and accumulate high amounts of Cd and Pb. Pot experiments were performed with soil containing Cd and Pb at concentrations of up to 180 mg kg^?1 and 2,400 mg kg^?1 respectively. All three plants showed high levels of tolerance. Borago officinalis; and Sinapis alba L. accumulated 109 mg kg^?1 and 123 mg kg^?1 Cd, respectively at the highest Cd spiked soil concentration. Phacelia boratus reached a Cd concentration of 42 mg kg^?1 at a Cd soil concentration of 100 mg kg^?1. In the case of Pb, B. officinalis and S. alba L. displayed Pb concentrations of 25 mg kg^?1 and 29 mg kg^?1, respectively at the highest Pb spiked soil concentration. Although the Pb uptake in P. boratus reached up to 57 mg kg^?1 at a Pb spiked soil concentration of 1,200 mg kg^?1, it is not suitable for phytoextraction because of its too low biomass.     

Detection of phloridzin in strawberries (Fragaria x ananassa Duch.) by HPLC-PDA-MS/MS and NMR spectroscopy

The phenolic profile of strawberry fruits (Fragaria x ananassa Duch., Rosaceae) was investigated by high-performance liquid chromatography with photodiode array detection. A peak displaying retention time and UV spectral data identical to those of phloridzin (phloretin 2'-O-beta-d-glucoside), a dihydrochalcone glucoside so far considered characteristic of apples, was monitored. For further characterization, crude extracts of strawberries were purified on polyamide, and the target compound was isolated by preparative and analytical HPLC. Structure elucidation was performed on the basis of APCI- and ESI-MS in the negative ion mode as well as by 1D and 2D NMR spectroscopy using authentic phloridzin for comparison. The d-configuration of the sugar moiety was established by HPLC analysis of the corresponding acyclic 1-deoxy-1-(N-acetyl-alpha-methylbenzylamino)alditol acetate. Apart from its chemotaxonomic relevance, this first report on the occurrence of phloridzin in strawberries is of particular interest for the authenticity control of strawberry products such as juices, jams, and fruit preparations since phloridzin has so far been used for the detection of fraudulent admixtures.     

Effects of nitrogen fertilization and irrigation on N2O emissions from a sandy soil in Germany

The aim of this study was to investigate the effect of supplemental irrigation on the amount of N₂O emissions on a sandy soil in north-east Germany. N₂O flux measurements were carried out over two vegetation periods from the emergence of plants to harvest. The level of N₂O emissions was low, which is typical for sandy soils in north-east Germany. In both periods, irrigation had no increasing effect on N₂O emissions. Relevant factors were the soil temperature and the soil water-filled pore space (WFPS), which were mainly influenced by weather conditions. This may indicate that nitrification was the main source of N₂O emissions. In conclusion, this study has confirmed that sandy soils under weather conditions of north-east Germany generally have a very low potential for N₂O emissions.     

Predictive relationship between polyphenol and nonfat cocoa solids content of chocolate

Chocolate is often labeled with percent cocoa solids content. It is assumed that higher cocoa solids contents are indicative of higher polyphenol concentrations, which have potential health benefits. However, cocoa solids include polyphenol-free cocoa butter and polyphenol-rich nonfat cocoa solids (NFCS). In this study the strength of the relationship between NFCS content (estimated by theobromine as a proxy) and polyphenol content was tested in chocolate samples with labeled cocoa solids contents in the range of 20-100%, grouped as dark (n = 46), milk (n = 8), and those chocolates containing inclusions such as wafers or nuts (n = 15). The relationship was calculated with regard to both total polyphenol content and individual polyphenols. In dark chocolates, NFCS is linearly related to total polyphenols (r2 = 0.73). Total polyphenol content appears to be systematically slightly higher for milk chocolates than estimated by the dark chocolate model, whereas for chocolates containing other ingredients, the estimates fall close to or slightly below the model results. This shows that extra components such as milk, wafers, or nuts might influence the measurements of both theobromine and polyphenol contents. For each of the six main polyphenols (as well as their sum), the relationship with the estimated NFCS was much lower than for total polyphenols (r2 < 0.40), but these relationships were independent of the nature of the chocolate type, indicating that they might still have some predictive capabilities.     

Negligible contribution from roots to soil-borne phospholipid fatty acid fungal biomarkers 18:2ω6,9 and 18:1ω9

The phospholipid fatty acid biomarkers 18:1ω9, 18:2ω6,9 and 18:3ω3,6,9 are commonly used as fungal biomarkers in soils. They have, however, also been found to occur in plant tissues, such as roots. Thus, the use of these PLFAs as fungal biomarkers in sieved soil, which may still contain small remains of roots, has been questioned. We used data from a recent beech tree girdling experiment to calculate the contribution of roots to these biomarkers and were able to demonstrate that not more than 0.61% of 18:1ω9 and 18:2ω6,9 in sieved soil samples originated from roots (but 4% of 18:3ω3,6,9). Additionally, the abundance of the biomarker 18:2ω6,9 in the soil was found to be highly correlated to ectomycorrhizal root colonization, which further corroborates its fungal origin. PLFA biomarkers were substantially reduced in vital roots from girdled trees compared to roots of control trees (by up to 76%), indicating that the major part of PLFAs measured in roots may actually originate from ectomycorrhizal fungi growing inside the roots. We calculated, that even a near to 50% reduction in fine root biomass - as observed in the girdling treatment - accounted for only 0.8% of the measured decrease of 18:2ω6,9. Our results demonstrate that both 18:1ω9 and 18:2ω6,9 are suitable biomarkers for detecting fungal dynamics in soils and that especially 18:2ω6,9 is a reliable biomarker to study mycorrhizal dynamics in beech forests.     

Chondrules with peculiar REE patterns: implications for solar nebular condensation at high C/O

Rare earth element (REE) data from two ordinary chondrite chondrules show distinct negative chondrite-normalized concentration anomalies of samarium, europium, and ytterbium. The peculiar patterns may be the result of REE gas/solid fractionation at an oxygen fugacity lower than has been assumed for the canonical solar nebula. We suggest that the two ordinary chondrite chondrules acquired the fractionated REE patterns by incorporation of highly reduced, ultrarefractory condensates in their precursors. This interpretation implies that high-temperature condensation processes occurred in nebular environments with a strong deficit in oxygen, such as regions with an enhanced carbon/oxygen ratio.     

Hydrogen isotopes in Eocene river gravels and paleoelevation of the Sierra Nevada

We determine paleoelevation of the Sierra Nevada, California, by tracking the effect of topography on precipitation, as recorded in hydrogen isotopes of kaolinite exposed in gold-bearing river deposits from the Eocene Yuba River. The data, compared with the modern isotopic composition of precipitation, show that about 40 to 50 million years ago the Sierra Nevada stood tall (>/=2200 meters), a result in conflict with proposed young surface uplift by tectonic and climatic forcing but consistent with the Sierra Nevada representing the edge of a pre-Eocene continental plateau.