University of Hohenheim

About: University of Hohenheim is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Population & Soil water. The organization has 8585 authors who have published 16406 publications receiving 567377 citations.

Tropical browses: contents of phenolic compounds, in vitro gas production and stoichiometric relationship between short chain fatty acid and in vitro gas production

Abstract: The contents of phenolic compounds, protein precipitation capacity (PPC) and in vitro gas production of tropical browse species were evaluated The stoichiometric relationship between in vitro gas measured on incubation of tannin-containing browses in buffered rumen fluid and calculated from short chain fatty acid (SCFA) production was investigated Crude protein (CP) contents in the browses ranged from 54 to 300 g/kg dry matter (DM) Total phenol (TP), tannins (T) and condensed tannins (TP and T as tannic acid equivalent; CT, as leucocyanidin equivalent) ranged from 17-250, 7-214, and 0-260 g/kg DM respectively, and PPC from 0 to 1066 μg BSA precipitated/g DM CP content of browses was negatively correlated with TP T, CT and PPC A significant correlation was observed between per cent change in gas production on addition of polyethylene glycol (PEG) and the contents of phenolics (r = 076 for both TP and T) Addition of PEG to tannin-containing browses increased in vitro gas production PPC was significantly correlated with TP (r = 087; P 005) The relationship between in vitro gas measured on incubation of browse leaves and that calculated from SCFA allows prediction of SCFA from gas production

Involvement of trichothecenes in fusarioses of wheat, barley and maize evaluated by gene disruption of the trichodiene synthase (Tri5) gene in three field isolates of different chemotype and virulence.

Abstract: SUMMARY Fusarium graminearum is the main causative agent of Fusarium head blight on small grain cereals and of ear rot on maize. The disease leads to dramatic yield losses and to an accumulation of mycotoxins. The most dominant F. graminearum mycotoxins are the trichothecenes, with deoxynivalenol and nivalenol being the most prevalent derivatives. To investigate the involvement of trichothecenes in the virulence of the pathogen, the gene coding for the initial enzyme of the trichothecene pathway was disrupted in three field isolates, differing in chemotype and in virulence. From each isolate three individual disruption mutants were tested for their virulence on wheat, barley and maize. Despite the different initial virulence of the three wild-type progenitor strains on wheat, all disruption mutants caused disease symptoms on the inoculated spikelet, but the symptoms did not spread into other spikelets. On barley, the trichothecene deficient mutants showed no significant difference compared to the wild-type strains: all were equally aggressive. On maize, mutants derived from the NIV-producing strain caused less disease than their wild-type progenitor strain, while mutants derived from DON-producing strains caused the same level of disease as their progenitor strains. These data demonstrate that trichothecenes influence the virulence of F. graminearum in a highly complex manner, which is strongly host as well as moderately chemotype specific.

The Native Rat Olfactory Cyclic Nucleotide-Gated Channel Is Composed of Three Distinct Subunits

Abstract: Cyclic nucleotide-gated (CNG) channels play central roles in visual and olfactory signal transduction. In the retina, rod photoreceptors express the subunits CNCa1 and CNCb1a. In cone photoreceptors, only CNCa2 expression has been demonstrated so far. Rat olfactory sensory neurons (OSNs) express two homologous subunits, here designated CNCa3 and CNCa4. This paper describes the characterization of CNCb1b, a third subunit expressed in OSNs and establishes it as a component of the native channel. CNCb1b is an alternate splice form of the rod photoreceptor CNCb1a subunit. Analysis of mRNA and protein expression together suggest coexpression of all three subunits in sensory cilia of OSNs. From single-channel analyses of native rat olfactory channels and of channels expressed heterologously from all possible combinations of the CNCa3, -a4, and -b1b subunits, we conclude that the native CNG channel in OSNs is composed of all three subunits. Thus, CNG channels in both rod photoreceptors and olfactory sensory neurons result from coassembly of specific a subunits with various forms of an alternatively spliced b subunit.

Breeding wheat and rye for resistance to Fusarium diseases

Abstract: Fusarium culmorum and F. graminearum Groups 1 and 2 cause seedling blight, crown rot, foot rot and head blight in wheat and rye that may affect grain yield and quality for baking and feeding. This review starts with an analysis of Fusarium populations with regard to their genetic variation for aggressiveness, mycotoxin production, and isolate-by-host genotype interaction. To assess resistance in the different host growth stages, quantitative inoculation and disease assessment techniques are necessary. Based on estimated population parameters, breeding strategies are reviewed to improve Fusarium resistance in wheat and rye. Epidemiological and toxicological aspects of Fusarium resistance that are important for resistance breeding are discussed. F. culmorum and F. graminearum display large genetic variation for aggressiveness in isolate collections and in naturally occurring populations. The production of mycotoxins, especially deoxynivalenol and its derivatives, is a common trait in these populations. Significant isolate-by-host genotype interactions were not found across environments in wheat and rye. Artificial infections in the field are indispensable for improving Fusarium crown rot, foot rot and head blight resistance in wheat and rye. For a reliable disease assessment of large populations, disease severity ratings were found to be the most convenient. The differentiation of host resistance is greatly influenced by an array of nongenetic factors (macro-environment, microclimate, host growth stage, host organ) that show significant interactions with host genotype. Selection for environmentally stable resistance has to be performed in several environments under a maximum array of different infection levels. Selection in early growth stages or on one plant organ does not in most cases allow prediction of resistance in adult-plant stages or another plant organ. Significant genetic variation for resistance exists for all Fusarium-incited diseases in breeding populations of wheat and rye. The patho-systems studied displayed a prevalence of additive gene action with no consistent specific combining ability effects and thus rapid progress can be expected from recurrent selection. In wheat, intensive testing of parental genotypes allows good prediction of the mean head blight resistance after crossing. Subsequent selection during selfing generations enables the use of transgression towards resistance. In hybrid breeding of winter rye, the close correlation between foot rot resistance of inbred lines and their GCA effects implies that selection based on the lines per se should be highly effective. This is not valid for F. culmorum head blight of winter rye caused by a greater susceptibility of the inbred lines compared to their crosses. For both foot rot and head blight resistance, a high correlation between the resistance to F. graminearum and F. culmorum was found in wheat and rye. Mycotoxin accumulation occurs to a great extent in naturally and artificially infected plant stands. The correlation between resistance traits and mycotoxin contents are medium and highly dependent on the environment. Further experiments are needed to clarify whether greater resistance will lead to a correlated reduction of the mycotoxin content of the grains under natural infection.

Contribution of the VA mycorrhizal hyphae in acquisition of phosphorus and zinc by maize grown in a calcareous soil

Abstract: An investigation was carried out to test whether the mechanism of increased zinc (Zn) uptake by mycorrhizal plants is similar to that of increased phosphorus (P) acquisition. Maize (Zea mays L.) was grown in pots containing sterilised calcareous soil either inoculated with a mycorrhizal fungus Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappe or with a mixture of mycorrhizal fungi, or remaining non-inoculated as non-mycorrhizal control. The pots had three compartments, a central one for root growth and two outer ones for hyphal growth. The compartmentalization was done using a 30-μm nylon net. The root compartment received low or high levels of P (50 or 100 mg kg−1 soil) in combination with low or high levels of P and micronutrients (2 or 10 mg kg−1 Fe, Zn and Cu) in the hyphal compartments. Mycorrhizal fungus inoculation did not influence shoot dry weight, but reduced root dry weight when low P levels were supplied to the root compartment. Irrespective of the P levels in the root compartment, shoots and roots of mycorrhizal plants had on average 95 and 115% higher P concentrations, and 164 and 22% higher Zn concentrations, respectively, compared to non-mycorrhizal plants. These higher concentrations could be attributed to a substantial translocation of P and Zn from hyphal compartments to the plant via the mycorrhizal hyphae. Mycorrhizal inoculation also enhanced copper concentration in roots (135%) but not in shoots. In contrast, manganese (Mn) concentrations in shoots and roots of mycorrhizal plants were distinctly lower, especially in plants inoculated with the mixture of mycorrhizal fungi. The results demonstrate that VA mycorrhizal hyphae uptake and translocation to the host is an important component of increased acquisition of P and Zn by mycorrhizal plants. The minimal hyphae contribution (delivery by the hyphae from the outer compartments) to the total plant acquisition ranged from 13 to 20% for P and from 16 to 25% for Zn.