Report of a collecting mission to the Georgian SSR 1983 for the study of indigenous material of cultivated plants

Summary In the summer 1983 the joint activities for the collection of autochthonous material of cultivated plants have been continued in the outermost western regions of Georgia (Abkhazia, Megrelia). Altogether 434 accessions could be obtained, more than one third of them being grain legumes, and one fourth vegetables and spice plants, resp. The remaining part includes mainly maize. Gene-erosion is very advanced especially for cereals and some grain legumes besidesPhaseolus vulgaris for which an astonishing genetic variability could be confirmed within the local material. Some details of the accessions regarding botanical interest and breeding value have been outlined. The collecting work should be continued.

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Bericht über eine Reise in die Georgische SSR 1983 zur Sammlung indigenen Materials von Kulturpflanzen

Zusammenfassung Im Sommer 1983 wurde eine weitere gemeinsame Reise zur Sammlung autochthonen Kulturpflanzenmaterials unternommen, die in die westlichen Teile von West-Georgien (Abchasien, Megrelien) führte. Es konnten insgesamt 434 Proben gesammelt werden, von denen mehr als ein Drittel Körnerleguminosen und je etwa ein Viertel Gemüse- und Gewürzpflanzen waren. Getreide war fast ausschließlich durch Mais vertreten. Die Gen-Erosion ist bei Getreide und einigen Körnerleguminosen bereits sehr weit fortgeschritten, während beiPhaseolus vulgaris wiederum eine erstaunliche Vielfalt an Formen festgestellt werden konnte. Besonders interessantes Material von Knoblauch, Blattkohlformen und einigen Spinatgemüsen wird kurz vorgestellt. Die Sammeltätigkeit sollte fortgesetzt werden.

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1983 .

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Oberflächenstrukturen und Eigenschaften von Permafrostböden im nordsibirischen Lena-Delta

Patterned ground and properties of permafrost soils of the Northsiberian Lena Delta The land surface of the Lena Delta is covered by polygon structures with scattered pingos and dunes. There exist so-called aerated, swampy and open polygons (open water surface) with Gelic Gleysols and Gelic Histosols (gelundic phase). The soils show only minor signs of cryoturbation and weathering. They contain high amounts of silt and slightly decomposed organic matter down to soil depths far beyond the permafrost table during summer. The soil surface is rising due to accumulation of organic matter and periodic flooding. This leads to a continuous rise of the permafrost table and subsequently to a permafrost freeze storage of plant material. The soils are therefore effective carbon sinks. On top of an investigated pingo a Gleyi-gelic Cambisol developed due to windexposed position, good drainage and higher soil temperatures connnected with a deeper permafrost table. This soil did not show any signs of cryoturbation. It has a relatively low content of organic matter due to a higher mineralization. As a consequence of frost effected sorting and wind erosion the soil material near to the surface is rich in sand and has a reduced silt content.     

Chromatographische Trennung von teerbürtigen PAK in einem Boden

Chromatographic separation of tarborne PAH in a soil At coal gas production sites soils are frequently infiltrated by fluid coal tar. From tar-filled pores a further diffusive and/or convective dispersion of PAH into the soil matrix occurs. Results from a contaminated site indicate, that the systematic change of the PAH congener pattern along the transport vector is due to differences in solubility and adsorption. This leads to a chromatographic fractionation of the initial PAH mixture with the least adsorbed congeneres forming the front of PAH translocation and the strongest adsorbed congeneres moving clearly slower.     

Taxonomic status and geographic provenance of germplasm accessions in the Solanum nigrum L. complex: AFLP data

Amplified Fragment Length Polymorphisms (AFLPs) were employed within the taxonomically difficult Solanum nigrum L. complex in order to characterize the genetic diversity present in a collection of the Gatersleben Genebank, to classify taxonomically unknown material, and to correlate the clustering of the examined accessions with their geographic origin. The results from AFLP analyses using two primer combinations on 44 entries from five species led to the detection of four major clusters, simultaneously uncovering significant differences in the levels of genetic diversity within or between species. S. americanumexhibited the highest infraspecific variation despite close geographic origins, simultaneously being placed in a clearly separated cluster in comparison to the other examined species of the complex. In addition, these other species showed even less interspecific variation than was found at the infraspecific level in S. americanum. In terms of taxonomy, the application of AFLPs helped in the classification of 13 black nightshade accessions formerly only listed as Solanum sp. This also was confirmed by morphological determination. Furthermore, one accession formerly classified as S. physalifolium var. nitidibaccatum i) clustered with AFLPs and ii) was identified morphologically as S. villosum. Contradictory classifications remain for two further entries from the same species, found within the S. nigrum cluster after AFLP analyses, while belonging to S. physalifolium var. nitidibaccatum according to herbarium specimen. Finally, as indicated by the information on provenance in geographically separated subclusters in S. americanum and partially in S. villosum, clues on the currently unknown origin of accessions from the genebank seem feasible by AFLP data.     

Irrigation with plant extracts in ecofarming increases biomass production and mineral and organic nitrogen content of plants

Seedlings of alfalfa, rape, spinach, and wheat, potted on sandy soil, were irrigated with an aqueous extract of pea shoot (PE, 9.84 g dry weight l^–1) or a solution of Ca, K, Mg, P, and NO₃‐N salts (SS) in a concentration similar to that in PE, for 31–48 days. In comparison to water‐irrigated controls, both SS and PE treated plants showed nearly equal increases in shoot dry weight (29–40 %), whereas PE‐treated plants had higher fresh weights (38–84 %) due to increased succulence. Treatment with SS did not enhance, but sometimes even reduce, the concentrations of Ca, K, Mg, and several trace elements in shoot tissues. In contrast, PE‐treated plants had higher Ca, K, Mg, and organic N, but lower As and Ni contents and were thus of higher nutritive value. Reduced contents of metals in plant tissue correlated with their reduced solubility in the soil solution, which was not due to changes in pH. Fertilizer components such as K and Mg (metals of lower exchange intensity) were incorporated into the soil to release Ca, Sr, and Ba (metals of higher exchange intensity) and reduce the solubility of most trace elements and metal‐complexing humic substances. In addition, application of Ca precipitated heavy metals and humic complexes directly from the soil solution. This effect was partially overcome by PE. Its carboxylic acids could act as phytochelators of metal ions and as mobilizers of the highly diffusible humic substances which carry metals to roots. It is concluded that continuous PE application replaces the quantities of Ca, K, Mg, P, and organic N, but not of NO₃‐N consumed during plant growth. Using PE does not add any relevant quantities of toxic metals to the plant‐soil system.     

Generation of gut-homing IgA-secreting B cells by intestinal dendritic cells

Normal intestinal mucosa contains abundant immunoglobulin A (IgA)-secreting cells, which are generated from B cells in gut-associated lymphoid tissues (GALT). We show that dendritic cells (DC) from GALT induce T cell-independent expression of IgA and gut-homing receptors on B cells. GALT-DC-derived retinoic acid (RA) alone conferred gut tropism but could not promote IgA secretion. However, RA potently synergized with GALT-DC-derived interleukin-6 (IL-6) or IL-5 to induce IgA secretion. Consequently, mice deficient in the RA precursor vitamin A lacked IgA-secreting cells in the small intestine. Thus, GALT-DC shape mucosal immunity by modulating B cell migration and effector activity through synergistically acting mediators.     

Characterization and PCR-based Typing of Xanthomonas campestris pv. vesicatoria from Peppers and Tomatoes in Serbia

During the last two decades bacterial strains associated with necrotic leaf spots of pepper and tomato fruit spots were collected in Serbia. Twenty-eight strains isolated from pepper and six from tomato were characterized. A study of their physiological and pathological characteristics, and fatty acid composition analysis revealed that all of the strains belong to Xanthomonas campestris pv. vesicatoria. Being non-amylolytic and non-pectolytic, pathogenic on pepper but not on tomato, containing lower amounts of fatty acid 15 : 0 ante–iso, the pepper strains were designated as members of the A group of X. campestris pv. vesicatoria. However, the tomato strains hydrolyzed starch and pectate, caused compatible reactions on tomato but not on pepper, had higher percent of 15 : 0 ante–iso fatty acid, and were classified into B phenotypic group and identified as X. vesicatoria. PCR primers were developed which amplified conserved DNA regions related to the hrp genes of different strains of X. campestris pv. vesicatoria associated with pepper and tomato. Restriction analysis of the PCR product resulted in different patterns and enabled grouping of the strains into four groups. When xanthomonads isolated from pepper and tomato in Serbia were analyzed, they clustered into two groups corresponding to the grouping based on their physiological and pathological characteristics. According to the reaction of pepper and tomato differential varieties, the strains from pepper belong to races P7 and P8 and tomato strains belong to the race T2. All strains were sensitive to copper and streptomycin. Advantages and disadvantages of various bacterial spot management practices are discussed.     

Relation between soil organic matter and yield levels of nonlegume crops in organic and conventional farming systems

The aim of this study was to evaluate the interaction between yield levels of nonleguminous crops and soil organic matter (SOM) under the specific conditions of organic and conventional farming, respectively, and to identify implications for SOM management in arable farming considering the farming system (organic vs. conventional). For that purpose, correlations between yield levels of nonlegume crops and actual SOM level (C_org, N_t, C_hwe, N_hwe) as well as SOM‐level development were examined including primary data from selected treatments of seven long‐term field experiments in Germany and Switzerland. Yield levels of nonlegume crops were positively correlated with SOM levels, but the correlation was significant only under conditions of organic farming, and not with conventional farming treatments. While absolute SOM levels had a positive impact on yield levels of nonlegumes, the yield levels of nonlegumes and SOM‐level development over time correlated negatively. Due to an increased demand of N from SOM mineralization, higher yield levels of nonlegumes obviously indicate an increased demand for OM supply to maintain SOM levels. Since this observation is highly significant for farming without mineral‐N fertilization but not for farming with such fertilization, we conclude that the demand of SOM‐level maintenance or enhancement and thus adequate SOM management is highly relevant for crop production in organic farming both from an agronomical and ecological point of view. Under conventional management, the agronomic relevance of SOM with regard to nutrient supply is much lower than under organic management. However, it has to be considered that we excluded other possible benefits of SOM in our survey that may be highly relevant for conventional farming as well.     

Physical carbon‐sequestration mechanisms under special consideration of soil wettability

The protective impact of aggregation on microbial degradation through separation has been described frequently, especially for biotically formed aggregates. However, to date little information exists on the effects of organic‐matter (OM) quantity and OM quality on physical protection, i.e., reduced degradability by microorganisms caused by physical factors. In the present paper, we hypothesize that soil wettability, which is significantly influenced by OM, may act as a key factor for OM stabilization as it controls the microbial accessibility for water, nutrients, and oxygen in three‐phase systems like soil. Based on this hypothesis, the first objective is to evaluate new findings on the organization of organo‐mineral complexes at the nanoscale as one of the processes creating water‐repellent coatings on mineral surfaces. The second objective is to quantify the degree of alteration of coated surfaces with regard to water repellence. We introduce a recently developed trial that combines FTIR spectra with contact‐angle data as the link between chemical composition of OM and the physical wetting behavior of soil particles. In addition to characterizing the wetting properties of OM coatings, we discuss the implications of water‐repellent surfaces for different physical protection mechanisms of OM. For typical minerals, the OM loading on mineral surfaces is patchy, whereas OM forms nanoscaled micro‐aggregates together with metal oxides and hydroxides and with layered clay minerals. Such small aggregates may efficiently stabilize OM against microbial decomposition. However, despite the patchy structure of OM coating, we observed a relation between the chemical composition of OM and wettability. A higher hydrophobicity of the OM appears to stabilize the organic C in soil, either caused by a specific reduced biodegradability of OM or indirectly caused by increased aggregate stability. In partly saturated nonaggregated soil, the specific distribution of the pore water appears to further affect the mineralization of OM as a function of wettability. We conclude that the wettability of OM, quantified by the contact angle, links the chemical structure of OM with a bundle of physical soil properties and that reduced wettability results in the stabilization of OM in soils.