Der Einfluss des physiologischen Alters der Pflanzknollen auf die Ertragsbildung von Kartoffelsorten verschiedener Reifezeit

Zusammenfassung Durch kontinuierliche Untersuchungen wurden das Kraut- und Knollenwachstum bei 5 Sorten und 4 Varianten unterschiedlichen physiologischen Alters (Keimung zum Teil unter Licht) verfolgt. Das physiologische Alter beeinflusst die Ertragsbildung durch zwei entgegengesetzt wirkende Tendenzen. 1) Mit zunehmendem Alter wird die Vorauflaufentwicklung verkürzt und die Vegetationsperiode in günstigere meteorologische Bedingungen vorverlegt. 2) Durch altes Pflanzgut kann das Krautwachstum so stark gehemmt werden, dass die geringe photosynthetische Kapazit?t des Krautes verminderte Knollenwachstumsraten und damit einen geringeren Ertrag bei Abreife zur Folge hat. Bei frühen Sorten wurde durch junges Pflanzgut, bei sp?ten Sorten durch Pflanzgut mittleren Alters die günstigste Krautentwicklung erreicht. Die Zahl der oberirdischen Stengel (einschliesslich gr?sserer Verzweigungen) und Knollen der frühen Sorten nahmen mit zunehmendem Alter des Pflanzgutes ab.

---

Summary The effect of the physiological age of seed tubers on yield was studied using 4 treatments of various ages (extremes of treat ent: accumulated temperature, 300–400 day-degrees>0°C, chitting to 3 mm; 200 day-degree>0°C, light chitting to 30 mm). Five cultivars in maturity classes ‘first early’ to ‘mid-late’ were examined over a 4-year period by experimental liftings and measurements of haulm growth. Increased physiological age accelerated emergence, but the time between emergence and tuber initiation, and between emergence and senescence was not affected (Table 1; Figs 1, 2). The total stem number (above-ground stems including concealed ones, which were inserted below half the maximum plant height) and the tuber number per plant of early cultivars decreased significantly with increased age of the seed tubers in spring (Figs 3,6). In one year there were higher stem numbers, but not tuber numbers, with greatly increased physiological age, due to dying-off of the apices of light chitted material (Fig. 3). The total stem numbers and tuber numbers of the mid-late cultivars were not affected significantly by the physiological age of the seed tubers (Figs 3,6). Haulm elongation was checked by increased physiological age of the seed tubers (Table 2). The physiologically youngest seed of the early cultivars had the greatest quantity of haulm and leaf weight up to the time of tuber initiation (Tables 2, 3; Figs 1, 2a). With the mid-late cultivars, seed of more advanced physiological age gave as good or even better haulm development up to tuber set (Table 2; Fig. 2b) as the physiologically youngest treatment. The effect of physiological age on yield development stemmed from two main factors. Firstly, the acceleration of emergence with increased age brought forward the vegetative period, in general, towards better conditions with regard to light and water supply. Secondly, increased age restricted haulm development thereby giving lower photosynthetic performance of the haulms up to the time of tuber formation, leading to reduced tuber growth rates or to an extension of the exponential part of the yield curve (Figs 1, 2a). The physiologically youngest seed of the early cultivars showed by tuber set the best haulm development and with it the highest yield potential (Figs 1, 2a), but there was no such advantage of young seed over seed of intermediate age for the mid-late cultivars (Fig. 2b). The yield at the end of the vegetation period is a consequence of both factors. The yield of the very early cultivars was strongly affected by the first, while the mid-late cultivars were affected principally by the advancing of the vegetative period (Fig. 5). Allowances had to be made when interpreting harvest yields for extremely unfavourable soil moisture conditions during the second half of the vegetative period of the experimental year (Fig. 4).

---

Résumé L'influence de l'age physiologique des plants sur le rendement a été examinée à l'aide de 4 variantes de plants d'ages physiologiques différents (variantes extrêmes: somme des températures: 300–400°C>0°C, germes jusqu'à 3 mm; 200 °C>0°C, germes colorés jusqu'à 30 mm), et de 5 variétés des groupes très précoces à mi-tardives, pendant 4 ans. Les examens ont porté sur des échantillonnages de récolte et des mesures de la croissance des fanes. Un age physiologique avancé a activé la levée. Les durées entre la levée et la tubérisation ainsi que levée-maturité n'ont pas été influencées (tabl. 1, fig. 1 et 2). Le nombre total de tiges (tiges axillaires situées sur la moitié inférieure des fanes comprises) et le nombre de tubercules par plante diminuait de manière significative au printemps chez les variétés précoces d'un age physiologique avancé (fig. 3 et 6). Certaines années, une augmentation du nombre de tiges mais non de celui de tubercules avec des plants d'un age physiologique avancé pouvait résulter du dessèchement apical des germes exposés à la lumière. Chez les variétés mi-tardives, le nombre total de tiges et tubercules n'a pas été influencé par les différents ages physiologiques (fig. 3 et 6). Un age physiologique avancé des plants (tabl. 2) a freiné la croissance des fanes. Les plants jeunes de variétés précoces ont produit, jusqu'au moment de la formation des tubercules, la plus grande masse de tiges et feuilles (tabl. 2 et 3, fig. 1 et 2a). Chez les variétés mi-tardives les plants d'un age plus avancé donnèrent une croissance des fanes égale ou parfois meilleure que les plants les plus jeunes (tabl. 2, fig. 2b). L'effet de l'age physiologique sur le rendement se manifeste par deux facteurs principaux. Primo, par l'accélération de la levée due à un age plus avancé, la période de végétation se situera (en général) dans la saison la plus favorable pour ce qui concerne le rayonnement et le ravitaillement en eau. Secondo, l'age avancé des plants inhibe la croissance des fanes et parlà l'activité de la photosynthèse lors de la formation et la croissance des tubercules, ce qui a pour conséquence une prolongation de la partie exponentielle de la courbe de croissance (fig. 1 et 2a). Tandis que pour les variétés précoces, c'est le plant jeune qui a donné le meilleur rendement (fig. 1 et 2a). Chez les variétés mi-tardives le plant jeune ne présente aucun avantage par rapport au plant d'age moyen (fig. 2b). Le rendement en fin de période de végétation est la résultante des deux facteurs précités. Les rendements des variétés très précoces ont été très fortement influencés par le premier facteur, tandis que pour les variétés mi-tardives, c'est l'avancement de la période de végétation qui a principalement été profitable (fig. 5). Lors de l'interprétation des rendements il s'agit également de tenir compte des conditions du sol très défavorables pendant la seconde moitié de la période de végétation (fig. 4).

     

Lindgomycin,an Unusual Antibiotic Polyketide from a Marine Fungus of the Lindgomycetaceae

An unusual polyketide with a new carbon skeleton, lindgomycin (1), and the recently described ascosetin (2) were extracted from mycelia and culture broth of different Lindgomycetaceae strains, which were isolated from a sponge of the Kiel Fjord in the Baltic Sea (Germany) and from the Antarctic. Their structures were established by spectroscopic means. In the new polyketide, two distinct domains, a bicyclic hydrocarbon and a tetramic acid, are connected by a bridging carbonyl. The tetramic acid substructure of compound 1 was proved to possess a unique 5-benzylpyrrolidine-2,4-dione unit. The combination of 5-benzylpyrrolidine-2,4-dione of compound 1 in its tetramic acid half and 3-methylbut-3-enoic acid pendant in its decalin half allow the assignment of a new carbon skeleton. The new compound 1 and ascosetin showed antibiotic activities with IC₅₀ value of 5.1 (±0.2) µM and 3.2 (±0.4) μM, respectively, against methicillin-resistant Staphylococcus aureus.     

Soil solution chemistry in the rhizosphere of beech (Fagus silvatica L.) roots as influenced by ammonium supply

Roots can induce significant changes in the rhizosphere soil. The aim of the present study was to investigate the influence of beech (Fagus silvatica L.) roots on the chemistry of the rhizosphere soil solution. Special emphasis was given to the effect of the NH₄⁺ supply since many forest soils presently receive high NH₄⁺ inputs from atmospheric deposition. In a mature beech stand, a non‐mycorrhized long root was forced to grow into a rhizotrone filled with homogenized acidic forest soil from the Bw horizon of a Dystric Cambisol. Beside the control, a NH₄⁺ enriched treatment was installed. Thirty micro suction cups of 1 mm diameter and 0.5 cm length were placed in a systematic grid of 5 × 10 mm in each rhizotrone to enable root growth through the grid. The water potential of the soil was kept constant by supplying a synthetic soil solution. Small amounts of soil solution were sampled periodically from May to October 1999 and analyzed by capillary electrophoresis for major cations and anions. Furthermore, pH and conductivity were measured by micro electrodes. In the laboratory experiments, beech seedlings were grown in rhizotrones in a control and in a NH₄⁺ fertilized soil. The equipment for sampling soil solutions and the soil conditions in the laboratory was similar to the field experiment. In each rhizotrone a single long root grew through the lysimeter grid. The laboratory conditions induced higher rates of nitrification as compared to the field. Thus, the overall concentration range of the soil solution was not comparable between field and laboratory studies. In all treatments average soil solution concentrations of H⁺ and Al³⁺ were significantly higher in the rhizosphere than in the bulk soil. The NH₄⁺ treatment resulted, in the field and laboratory, in a strong increase of the H⁺ and Al³⁺ concentrations in the rhizosphere, accompanied by an accumulation of Ca²⁺, Mg²⁺, and NO₃^—. The observed rhizosphere gradients in soil solution chemistry were highly dynamic in time. The results demonstrate that the activity of growing beech roots results in an acidification of the soil solution in the rhizosphere. The acidification was enhanced after the addition of NH₄⁺.     

RNA‐based biocontrol compounds: current status and perspectives to reach the market

Facing current climate challenges and drastically reduced chemical options for plant protection, the exploitation of RNA interference (RNAi) as an agricultural biotechnology tool has unveiled possible new solutions to the global problems of agricultural losses caused by pests and other biotic and abiotic stresses. While the use of RNAi as a tool in agriculture is still limited to a few transgenic crops, and only adopted in restricted parts of the world, scientists and industry are already seeking innovations in leveraging and exploiting the potential of RNAi in the form of RNA‐based biocontrol compounds for external applications. Here, we highlight the expanding research and development pipeline, commercial landscape and regulatory environment surrounding the pursuit of RNA‐based biocontrol compounds with improved environmental profiles. The commitments of well‐established agrochemical companies to invest in research endeavours and the role of start‐up companies are crucial for the successful development of practical applications for these compounds. Additionally, the availability of standardized guidelines to tackle regulatory ambiguities surrounding RNA‐based biocontrol compounds will help to facilitate the entire commercialization process. Finally, communication to create awareness and public acceptance will be key to the deployment of these compounds. © 2019 Society of Chemical Industry     

Development of a dot blot assay for the rapid detection of central nervous system tissue on meat and contact surfaces

As a potential transmitter of bovine spongiform encephalopathy (BSE), tissue from bovine central nervous system (CNS) is not accepted in meat and meat products. Western blot analysis of the CNS marker myelin proteolipid protein (PLP) detects CNS contamination selectively and sensitively. In this study, a rapid dot blot assay using an anti-PLP antibody was developed to screen CNS contamination of meat and contact surfaces. The detection limit was 0.01% bovine brain in minced bovine muscle. When applied to a swab test, down to 0.5 mg of CNS tissue on meat or other surfaces was detectable. Other offal tissues or peripheral nerves did not interfere with the assay. The test allows a differentiation between mammalian and avian CNS but not among mammalian species. The swab test was applied immediately after slaughtering at several areas of the bovine head. CNS was not detectable at any region which may enter the food chain.     

Growth response of 98 barley (Hordeum vulgare L.) genotypes to elevated CO2 and identification of related quantitative trait loci using genome‐wide association studies

Elevated CO₂ (eCO₂) concentrations can stimulate crop growth, but little is known about intraspecific variability in the response to eCO₂ and the underlying genetics in cereals. Field experiments over two years with 98 barley genotypes were conducted in open‐top chambers (OTCs) under ambient CO₂ (400 ppm) and eCO₂ (700 ppm) concentrations. At crop maturity, different fractions of aboveground biomass (AGB) were measured, and genome‐wide association studies (GWASs) were conducted to identify quantitative trait loci (QTL). Averaged across all genotypes, eCO₂ significantly enhanced AGB by 15%, while the increase in culm and ear biomass alone was not significant. The AGB response to eCO₂ of the individual genotypes ranged from c. ?36% to +95% compared with ambient CO₂ (aCO₂), showing a large variability of growth responses. In GWAS, 51 associations between SNP markers and the relative changes (eCO₂/aCO₂) in biomass were detected on different chromosomes. Loci potentially involved in biomass alterations under eCO₂ were identified. The wide range of variability in responses might be exploited by marker‐based breeding for climate‐resilient barley.     

The raccoon (Procyon lotor) as potential rabies reservoir species in Germany: a risk assessment

Terrestrial wildlife rabies has been successfully eliminated from Germany predominantly as a result of the distribution of oral rabies vaccine baits. In case that wildlife rabies would re-emerge among its known reservoir species in Germany, swift action based on previous experiences could spatially and temporally limit and subsequently control such an outbreak. However, if rabies emerged in the raccoon population in Germany (Procyon lotor), there are no tools or local experience available to cope with this situation. This is especially worrisome for urban areas like Kassel (Hesse) due to the extremely high raccoon population density. A rabies outbreak among this potential reservoir host species in these urban settings could have a significant impact on public and animal health.     

Fungal colonisation of outside weathered modified wood

Specimens of Scots pine sapwood (Pinus sylvestris L.) and beech wood (Fagus sylvatica L.) were treated with an amino-alkyl-functional oligomeric siloxane, a sodium water glass solution and 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU). Treated and untreated wood specimens were exposed outdoors without ground contact. After 9?months of outside exposure, all specimens showed discolouration caused by infestations of mould and staining fungi on the exposed wood surface. Fungi grown on the sample surface were isolated and identified by microscopic technique and sequencing of PCR-amplified DNA from the ITS region. Primarily, an infestation by ascomycetes and related deuteromycetes was found. The most dominant fungi were Trichoderma sp. and Epicoccum sp.. An infestation of Aureobasidium pullulans was only detected on untreated and DMDHEU-treated samples. There were only marginal differences of fungal infestation between the two wood species.