Buchbesprechungen

Ohne Zusammenfassung     

Verbreitung der TannentrieblausDreyfusia Nüsslini C.B. in Österreich und neue Methoden der Bekämpfung

Ohne Zusammenfassung     

IPM Strategies and Their Dilemmas Including an Introduction to www. eurowheat.org

Information about disease management in winter wheat （Triticum aestiva） in eight European countries was collated and analysed by scientists and extension workers within the European Network for the Durable Exploitation of Crop Protection Strategies （ENDURE）. This included information about specific disease thresholds, decision support systems, host varieties, disease prevalence and pathogen virulence. Major differences in disease prevalence and economic importance were observed. Septoria tritici blotch （Mycosphaerella graminicola） was recognized as the most yield reducing disease in countries with intensive wheat production, but also rust diseases （Puccinia striiformis and Puccinia triticina）, powdery mildew （Blumeria graminis） and Fusarium head blight （Fusarium spp.） were seen as serious disease problems. Examples of current integrated pest management （IPM） strategies in different countries have been reported. Disease management and fungicide use patterns showed major differences, with an average input equivalent to 2.3 full dose rates （TFI） in the UK and a TFI of 0.6 in Denmark. These differences are most likely due to a combination of different cropping systems, climatic differences, disease prevalence, and socio-economic factors. The web based information platform www.eurowheat.org was used for dissemination of information and results including information on control thresholds, cultural practices which can influence disease attack, fungicide efficacy, fungicide resistance, and pathogen virulence, which are all elements supporting 1PM for disease control in wheat. The platform is open to all users. The target groups of EuroWheat information are researchers, advisors, breeders, and similar partners dealing with disease management in wheat.     

Podzol: Soil of the Year 2007. A review on its genesis,occurrence, and functions

The Podzol has been elected “Soil of the year 2007” in Germany. This article reviews the present knowledge on the development, functions, and threats of Podzols. The main theories on mobilization and transport of organic matter, Fe, Al, and Si are (1) metal‐organic migration, (2) metal reduction, and (3) inorganic sol migration. Immobilization theories include precipitation or polymerization due to increasing pH/abundance of base cations with depth, mechanical filtering in soil pores, oxidation of metal‐organic complexes, biodegradation of the organic part, decreasing C‐to‐metal ratios during translocation, adsorption to soil particles, and flocculation at the point of zero charge. Podzolization is discussed also on the catena scale, where vertical and lateral translocation processes (across pedon boundaries) need to be considered to understand Podzol patterns in landscapes. Chronosequence studies show that incipient podzolization usually becomes visible between 100 and 500 y and mature Podzols develop in 1,000–6,000 y. The occurrence of Podzols worldwide is concentrated mainly on the boreal zone and mountain regions within the humid temperate zone. Smaller Podzol areas are found in some perhumid tropical and subtropical regions. In Germany, Podzols occur in the Alps, in the glaciofluvial valleys and heathlands of N Germany, and in the mountain ranges. They fulfil several ecological functions, especially for groundwater recharge. Main threats for these mostly sandy soils are wind erosion and surface mining of sand. Two pedons which were chosen to represent the “Soil of the year 2007” are presented. Finally, some conclusions about podzolization processes are drawn, which may explain the diverse observations reported in the literature.     

Basaltverwitterung und Bodenentwicklung seit dem mittleren Tertiär auf Lanzarote,Kanarische Inseln (Profil Malaya Chica)

Basalt Weathering and Soil Development since the Middle Tertiary on Lanzarote, Canary Islands - The Profile Malaya Chica A polygenetic soil on tertiary (miocene) basalt in the north of Lanzarote (Canary Islands, Spain) was examined. Soil development was reconstructed, which took place in a semiarid climate since the end of the tertiary period. The interpretation of field and laboratory results (carbonate, grainsize distribution, oxalate and dithionithe soluble oxides, CEC, clay minerals, micromorphology) explained the history of development. Since the miocene at least seven consecutive phases of soil development took place induced by erosion, volcanic and colluvial sedimentation and/or climatic changes.     

Consequences of sodium exclusion for the osmotic potential in the rhizosphere – Comparison of two maize cultivars differing in Na+ uptake

According to the biphasic model of growth response to salinity, growth is first reduced by a decrease in the soil osmotic potential (Ψ_o), i.e., growth reduction is an effect of salt outside rather than inside the plant, and genotypes differing in salt resistance respond identically in this first phase. However, if genotypes differ in Na⁺ uptake as it has been described for the two maize cultivars Pioneer 3906 and Across 8023, this should result in differences in Na⁺ concentrations in the rhizosphere soil solution and thus in the concentration of salt outside the plant. It was the aim of the present investigation to test this hypothesis and to investigate the effect of such potential differences in soil Ψ_o caused by Na⁺ exclusion on plant water relations. Sodium exclusion at the root surface of intact plants growing in soil was investigated by sampling soil solution from the rhizosphere of two maize cultivars (Across 8023, Pioneer 3906). Plants were grown in a model system, consisting of a root compartment separated from the bulk soil compartment by a nylon net (30 μm mesh size), which enabled independent measurements of the change of soil solution composition and soil water content with increasing distance from the root surface (nylon net). Across 8023 accumulated higher amounts of sodium in the shoot compared to the excluder (Pioneer 3906). The lower Na⁺ uptake in the excluder was partly compensated by higher K⁺ uptake. Pioneer 3906 not only excluded sodium from the shoot but also restricted sodium uptake more efficiently from roots relative to Across 8023. This was reflected by higher Na⁺ concentrations in the rhizosphere soil solution of the excluder 34 days after planting (DAP). The difference in Na⁺ concentration in rhizosphere soil solution between cultivars was neither due to differences in transpiration and thus in mass flow, nor due to differences in actual soil water content. As the lower Na⁺ uptake of the excluder (Pioneer 3906) was only partly compensated by increased uptake of K⁺, soil Ψ_o in the rhizosphere of the excluder was more negative compared to Across 8023. However, no significant negative effect of decreased soil Ψ_o on plant water relations (transpiration rate, leaf Ψ_o, leaf water potential, leaf area) could be detected. This may be explained by the fact that significant differences in soil Ψ_o between the two cultivars occurred only towards the end of the experiment (27 DAP, 34 DAP).     

Male gamete development and early tapetal degeneration in cytoplasmic male-sterile pepper investigated by meiotic, anatomical and ultrastructural analyses

Cytoplasmic male‐sterile (CMS) pepper (Capsicum annuum L.) is a useful germplasm for heterosis breeding, however, the process of male gamete development and the sterility mechanism is unclear. In the present study, the developmental sequence in CMS pepper and the causative factors responsible for pollen abortion were investigated through combined meiotic analysis, paraffin section observations, and transmission electron microscopy. Results from meiotic analysis showed that meiosis in a male‐sterile inbred line, CMS 21A, was normal, and uni‐nucleate pollen could be released from the tetrads of both CMS 21A and the fertile maintainer line 21B. However, only the uni‐nucleate pollen from CMS 21B could develop into functional gametes, while the uni‐nucleate pollen from the 21A went through a process of rupture, and the cellular components were released into the anther sac. Observations of paraffin sections viewed with the light microscope showed that the tapetum of CMS 21A at the uni‐nucleate stage swelled abnormally and was pressed against pollen grains of the locule. Further observations with transmission electron microscopy revealed that the mitochondria in CMS 21A tapetum were highly vacuolated, and there was no accumulation of sporopollenin on the surface of CMS 21A pollen, suggesting a close relationship between early degeneration of tapetum and CMS.     

Meiotic chromosome behaviour in an allotriploid derived from an amphidiploid × diploid mating in Cucumis

A synthetic amphidiploid species Cucumis hyriviis Chen & Kirkbride (2n = 4x = 38; genome designated as HHCC) has recently been created from an interspecific mating between C. sativus L. (2n = 2x = 14: genome designated as CC) and C. hystrx. Chakr. (2n = 2x = 24; genome designated as HH). This amphidiploid is resistant to root knot nematode, tolerant to low irradiance, and has higher nutritional value than standard processing cucumber cultivars. An allotriploid (2n = 3x = 26; HCC) was derived from a cross between C. sativus L. and C. hytivus Chen & Kirkbride. Diploid meiotic behaviour in C. sativus and C. hystrix involves the development of seven and 12 metaphase bivalents respectively. In the derived allotriploid. univalents. bivalents, and trivalents (at relatively low frequency) were observed at metaphase I indicating that some homeologues from the C and H genomes can synapse. Based on a comparative karyotype analysis of cucumber (i.e. chromosome size and pairing behaviour) and aliotriploid plants, the seven bivalents observed at metaphase I were ascertained to be cucumber homologues, while the 12 univalents were of C. hystrix origin thus confirming the allotriploid karyotypic constitution to be HCC. On average, the frequency of trivalents was 0.24 at diakinesis and 0.22 in 100 meiocytes at metaphase I. indicating the possibility of genetic exchange due to the homoeology between the C and H genomes. After simultaneous cytokinesis, only polyads were observed in pollen mother cells (PMCs) at telophase II, which led to the production of sterile pollen grains. Multi‐polarization of chromosomes was dominant at anaphase II. However. in about 20% PMCs. chromosomes separated to form a 7C + 1‐2H complement, suggesting a possible method for the production of alien addition cucumber‐C hystrix lines through further backcrossing of the allotriploid to diploid cucumber.