Improving the efficiency and effectiveness of global phosphorus use: focus on root and rhizosphere levels in the agronomic system

Phosphorus (P) is essential for life and for efficient crop production, but global P use with limited recycling is inefficient in several sectors, including agronomy. Unfortunately, plant physiologists, agronomists, farmers and end users employ different measures for P use efficiency (PUE), which often masks their values at different scales. The term P use effectiveness, which also considers energetic and sustainability measures in addition to P balances, is also a valuable concept. Major physiological and genetic factors for plant P uptake and utilization have been identified, but there has been limited success in genetically improving PUE of modern crop cultivars. In maize, studies on root architectural and morphological traits appear promising. Rhizosphere processes assist in mobilizing and capturing sparingly soluble phosphate from rock phosphate. Combinations of phosphate-solubilizing microorganisms with ammonium-based nitrogen fertilizer, as well as strategies of fertilizer placement near the roots of target crops, can moderately enhance PUE. The desired concentration of P in the products differs, depending on the final use of the crop products as feed, food or for energy conversion, which should be considered during crop production.     

Antibody titer against bovine viral diarrhea virus (BVDV) in bulk milk samples from Bavaria

A total of 5204 bulk milk samples were tested for antibodies against bovine viral diarrhea virus (BVDV) classified according to the scheme after Alenius. Forty-five percent of the samples from 2002 were classified as class 0 and class 1, 55% as class 2 and 3. 6420 bulk milk samples from 1997 were classified in an independent study in 65.6% class 0 and 1 and 34.4% in class 2 and 3. In class 0 and class 1 farms only very rarely persistent viremic animals have been found, whereas in class 2 and 3 their presence is highly likely. Our studies with non-selected sera defined the serological screening of bulk milk samples as a promising tool for a possible BVDV eradication program in Bavaria.     

Feasibility of serological bulk milk testing as a method for BVD surveillance

A commercial ELISA detecting antibodies against bovine viral diarrhoea Virus (BVDV) was analysed for its applicability for bulk-milk screening. Detection limits were analysed using native and concentrated milk samples (milk treated with rennet and ammonium sulfate precipitated) from 10 cows whose sera showed different reactivity levels in the ELISA and from two cows which gave birth to persistently infected calves during the last year. Further this and a second commercial ELISA were used to screen 591 randomly selected bulk-milk samples. To clarify discrepancies thirty-nine herds were included in a follow-up study. A second bulk-milk sample and serum samples from 10 young cattle of 6 to 28 month of age per herd were analysed for antibodies against BVDV. The results of this second testing and the detection of viremic animals in 4 herds confirmed the results from initial bulk-milk testing with both tests. The analysed test is suitable for bulk-milk testing although its application is limited by vaccination.     

Distribution of structure and lignin within growth rings of Norway spruce

A radial core from a Norway spruce (Picea abies (L.) Karst.) estimated to be about 107 years old was cut from a board and was analyzed for density and microfibril angle (MFA). Furthermore, cell geometry, wall thickness and lignin distribution were analyzed on three selected growth rings in detail. Intra-ring differences in the density profiles are also true for cell wall thicknesses as well as radial and tangential lumen diameters. A higher MFA was found for earlywood with a slow decrease toward the latewood region. The lignin was found to remain rather constant throughout the growth rings, which suggests a constant chemical composition of the cell wall material within the growth ring. From the recorded datasets on a cellular level, it can be concluded that the main adaptation regarding structure–property relationships toward the optimization of water transport and mechanical stability is mainly achieved at the cell level.     

Age estimation in the harbour seal (Phoca vitulina) based on the closure of skull sutures and synchondroses

Age estimation of individuals is an important tool for the management of marine mammals and is mostly done by microscopic analysis of growth layer groups (GLGs) in teeth (cementum and dentin) and bone. The present study evaluated the use of sutural and synchondrosal closure in the skull of the harbour seal (Phoca vitulina) as a potential non-destructive alternative for age estimation. For that, we scored the ectocranial closure of 12 selected sutures and synchondroses in a sample of 303 Eastern Atlantic harbour seals (P. v. vitulina; 138 males, 165 females), for which data on age at death were available, based on determined gross-morphological criteria in individuals younger than 1 year and cement layer analysis in canines in older individuals. A strong positive relationship between the sum of closure level scores (SCS) and age (males: r = 0.8797, females: r = 0.8825) was recorded, which was stronger than that for the relationship between age and condylobasal length (CBL, males: r = 0.7085, females: 0.7086) (all p-values <0.0001). In adult individuals (≥5 years), CBL was higher in males than females (p < 0.0001), while SCS did not significantly differ between the two sexes (p = 0.148). Our findings show that the analysis of sutural/synchondrosal closure is a valid alternative for age estimation in harbour seals, thereby confirming results of previous studies on other pinniped species.     

The Amazonian dwarf cichlid Apistogramma agassizii (Steindachner, 1875) is a geographic mosaic of potentially tens of species: Conservation implications

1. Assessing biodiversity and understanding how it works is a prerequisite for species conservation. The Amazon basin is one of the main biodiversity hotspots where fish are heavily exploited for ornamental purposes.
2. The ornamental trade heavily exploits the genus Apistogramma, which is one of the most species‐rich among Neotropical cichlids with 94 formally described species. This number is certainly underestimated owing to the limitations of conventional taxonomy, which is still too often based solely on morphological criteria and sometimes on few individuals.
3. Most species of this genus have a high degree of endemism and are highly prized on the ornamental market, which could put them at risk. A few species are supposed to have extensive distributions, and in particular Apistogramma agassizii, present from the Amazon estuary up to the Ucayali and Marañon rivers in Peru.
4. This study assessed the taxonomic status of 1,151 specimens of A. agassizii collected from 35 sites around Iquitos in the Peruvian Amazon. On the basis of molecular analyses (nuclear and mitochondrial DNA) and mate choice experiments, at least three biological species within the nominal A. agassizii were evidenced in the sampling area, which is extremely small compared with the known distribution of the species as initially described.
5. According to the molecular calibrations, these three species would have diverged during the Plio‐Pleistocene. Two of them seem to be endemic from small sub‐basins, one from the Nanay River and the other from the Apayacu/Ampiyacu systems. A possible scenario that may explain the evolutionary history of these species is proposed.
6. The conservation implications of these results on the estimation of the diversity of A. agassizii, of Apistogramma species in general, and of other Amazonian cichlids are discussed.

     

Chromosome location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L.) 1. Mlk and other alleles at the Pm3 locus

Summary Several wheat cultivars/lines were inoculated with isolates of Erysiphe graminis tritici to identify new genes/alleles for resistance. The wheats were tested with 13 isolates that had been characterized from responses on differential lines with known resistance genes. Gene Mlk which occurs in cultivars Kolibri, Syros, Ralle and several other European common wheats was found to be an allele at the Pm3 locus and is now designated Pm3d. The mildew resistance in an old Australian wheat, W150, is conferred by a single gene also allelic to Pm3 and now designated Pm3e. The near-isogenic line Michigan Amber/8^*Cc possesses another allele now designated Pm3f. A Syrian land variety of common wheat shows mildew resistance that is conditioned by the combination of genes Pm1 and Pm3a. Finally, two accessions of Triticum aestivum ssp. sphaerococcum appeared to possess the Pm3c allele.     

Carbon flow into microbial and fungal biomass as a basis for the belowground food web of agroecosystems

The origin and quantity of plant inputs to soil are primary factors controlling the size and structure of the soil microbial community. The present study aimed to elucidate and quantify the carbon (C) flow from both root and shoot litter residues into soil organic, extractable, microbial and fungal C pools. Using the shift in C stable isotope values associated with replacing C3 by C4 plants we followed root- vs. shoot litter-derived C resources into different soil C pools. We established the following treatments: Corn Maize (CM), Fodder Maize (FM), Wheat + maize Litter (WL) and Wheat (W) as reference. The Corn Maize treatment provided root- as well as shoot litter-derived C (without corn cobs) whereas Fodder Maize (FM) provided only root-derived C (aboveground shoot material was removed). Maize shoot litter was applied on the Wheat + maize Litter (WL) plots to trace the incorporation of C4 litter C into soil microorganisms. Soil samples were taken three times per year (summer, autumn, winter) over two growing seasons. Maize-derived C signal was detectable after three to six months in the following pools: soil organic C (C_org), extractable organic C (EOC), microbial biomass (C_mic) and fungal biomass (ergosterol). In spite of the lower amounts of root- than of shoot litter-derived C inputs, similar amounts were incorporated into each of the C pools in the FM and WL treatments, indicating greater importance of the root- than shoot litter-derived resources for the soil microorganisms as a basis for the belowground food web. In the CM plots twice as much maize-derived C was incorporated into the pools. After two years, maize-derived C in the CM treatment contributed 14.1, 24.7, 46.6 and 76.2% to C_org, EOC, C_mic and ergosterol pools, respectively. Fungi incorporated maize-derived C to a greater extent than did total soil microbial biomass.     

Estimation of clay content from easily measurable water content of air‐dried soil

Soil texture is one of the main factors controlling soil organic carbon (SOC) storage. Accurate soil‐texture analysis is costly and time‐consuming. Therefore, the clay content is frequently not determined within the scope of regional and plot‐scale studies with high sample numbers. Yet it is well known that the clay content strongly affects soil water content. The objective of our study was to evaluate if the clay content can be estimated by a simple and fast measure like the water content of air‐dried soil. The soil samples used for this study originated from four different European regions (Hainich‐Dün, Germany; Schwäbische Alb, Germany; Hesse, France; Bugac, Hungary) and were collected from topsoils and subsoils in forests, grasslands, and croplands. Clay content, water content of air‐dried soil, and SOC content were measured. Clay content was determined either by the Pipette method or by the Sedigraph method. The water content of air‐dried soil samples ranged from 2.8 g kg^–1 to 63.3 g kg^–1 and the corresponding clay contents from 60.0 g kg^–1 to 815.7 g kg^–1. A significant linear relationship was found between clay content and water content. The scaled mean absolute error (SMAE) of the clay estimation from the water content of air‐dried soil was 20% for the dataset using the Pipette method and 28% for the Sedigraph method. The estimation of the clay content was more accurate in fine‐textured than in coarse‐textured soils. In this study, organic‐C content played a subordinate role next to the clay content in explaining the variance of the water content. The water retention of coarse‐textured soils was more sensitive to the amount of organic C than that of fine‐textured soils. The results indicate that in our study the water content of air‐dried soil samples was a good quantitative proxy of clay contents, especially useful for fine‐textured soils.