Decomposition of maize residues after manipulation of colonization and its contribution to the soil microbial biomass

A 28-day incubation experiment at 12°C was carried out on the decomposition of maize leaf litter to answer the questions: (1) Is the decomposition process altered by chemical manipulations due to differences in the colonization of maize leaf litter? (2) Do organisms using this maize material contribute significantly to the soil microbial biomass? The extraction of the maize straw reduced its initial microbial biomass C content by 25%. Fumigation and extraction eliminated the microbial biomass by 88%. In total, 17% of added maize straw C was mineralized to CO₂ during the 28-day incubation at 12°C in the treatment with non-manipulated straw. Only 14% of added C was mineralized in the treatment with extracted straw as well as in the treatment with fumigated and extracted straw. The net increase in microbial biomass C was 79 μg g^?1 soil in the treatment with non-manipulated straw and an insignificant 9 μg g^?1 soil in the two treatments with manipulated straw. However, the net increase did not reflect the fact that the addition of maize straw replaced an identical 58% (≈180 μg g^?1 soil) of the autochthonous microbial biomass C₃-C in all three straw treatments. In the two treatments with manipulated straw, the formation of maize-derived microbial biomass C₄-C was significantly reduced by 25%. In the three straw treatments, the ratio of fungal ergosterol-to-microbial biomass C ratio showed a constant 60% increase compared to the control, and the contents of glucosamine and muramic acid increased by 18%. The average fungal C/bacterial C ratio was 3.6 in the soil and 5.0 in the recovered maize straw, indicating that fungal dominance was not altered by the initial chemical manipulations of the maize straw-colonizing microorganisms.     

Amino sugars as specific indices for fungal and bacterial residues in soil

Amino sugars are important indices for the contribution of soil microorganisms to soil organic matter. Consequently, the past decade has seen a great increase in the number of studies measuring amino sugars. However, some uncertainties remain in the interpretation of amino sugar data. The objective of the current opinion paper is to summarize current knowledge on amino sugars in soils, to give some advice for future research objectives, and to make a plea for the correct use of information. The study gives an overview on the origin of muramic acid (MurN), glucosamine (GlcN), galactosamine (GalN), and mannosamine (ManN). Information is also provided on measuring total amino sugars in soil but also on compound-specific δ¹³C and δ¹⁵N determination. Special attention is given to the turnover of microbial cell-wall residues, to the interpretation of the GlcN/GalN ratio, and to the reasons for converting fungal GlcN and MurN to microbial residue C. There is no evidence to suggest that the turnover of fungal residues generally differs from that of bacterial residues. On average, MurN contributes 7% to total amino sugars in soil, GlcN 60%, GalN 30%, and ManN 4%. MurN is highly specific for bacteria, GlcN for fungi if corrected for the contribution of bacterial GlcN, whereas GalN and ManN are unspecific microbial markers.     

Long-term amendment of four different compost types on a loamy silt Cambisol: impact on soil organic matter,nutrients and yields

This study investigated the long-term effects of different composts (urban organic waste compost (OWC), green waste compost (GWC), cattle manure compost (MC) and sewage sludge compost (SSC)) compared to mineral fertilisation on a loamy silt Cambisol, after a 7-year start-up period. The compost application rate was 175 kg N ha^?1, with 80 kg mineral N ha^?1 and without. Soil characteristics (soil organic carbon (SOC), carbon-to-nitrogen (C/N) ratio and soil pH), nutrients (nitrogen (N), phosphorous (P) and potassium (K)) and crop yields were investigated between 1998 and 2012. SOC concentrations were increased by compost applications, being highest in the SSC treatments, as for soil pH. N contents were significantly higher with compost amendments compared to mineral fertilisation. The highest calcium-acetate-lactate (CAL)-extractable P concentrations were measured in the SSC treatments, and the highest CAL-extractable K concentrations in the MC treatments. Yields after compost amendment for winter barley and spring wheat were similar to 40 kg mineral N ha^?1 alone, whereas maize had comparable yields to 80 kg mineral N ha^?1 alone. We conclude that compost amendment improves soil quality, but that the overall carbon (C) and N cycling merits more detailed investigation.     

Rubber intercropping: a viable concept for the 21st century?

The last decades brought along a tremendous expansion of rubber plantations as well as respective socio-economic transformations. This paper reviews the historical development of rubber cultivation with special reference to intercropping and illustrates the major development steps. The agronomic challenges of intercropping are analyzed and a management classification scheme is suggested. Though the topic of labor always accompanied rubber management, it is nowadays of even higher relevance due to alternative income options, be it due to competing crops such as oil palm, or be it off-farm income opportunities. This development challenges labor intensive permanent intercropping systems. It can thus be concluded that the permanent integration of additional plants needs either to be highly profitable or at least be labor extensive to be adopted on a considerable scale. Given the large area of rubber plantations the latter seems to be more realistic. In this context timber trees might offer promising options if tree selection is properly adapted to site and plantation conditions. Nevertheless, without external interventions, such as land-use planning and implementation, or incentives, the development will be difficult to control.     

Extracellular Metabolites from Industrial Microalgae and Their Biotechnological Potential

Industrial microalgae, as a big family of promising producers of renewable biomass feedstock, have been commercially exploited for functional food, living feed and feed additives, high-value chemicals in nutraceuticals, cosmeceuticals, and chemical reagents. Recently, microalgae have also been considered as a group that might play an important role in biofuel development and environmental protection. Almost all current products of industrial microalgae are derived from their biomass; however, large amounts of spent cell-free media are available from mass cultivation that is mostly unexploited. In this contribution we discuss that these media, which may contain a remarkable diversity of bioactive substances are worthy to be recovered for further use. Obviously, the extracellular metabolites from industrial microalgae have long been neglected in the development of production methods for valuable metabolites. With the advances in the last ten years, more and more structures and properties from extracellular metabolites have been identified, and the potential utilization over wide fields is attracting attention. Some of these extracellular metabolites can be potentially used as drugs, antioxidants, growth regulators or metal chelators. The purpose of this review is to provide an overview of the known extracellular metabolites from industrial microalgae which might be of commercial interest. The attention mainly focuses on the reports of extracellular bioactive metabolites and their potential application in biotechnology.     

Two Severe Cases of Tungiasis in Goat Kids in Uganda

Tungiasis ensues from the penetration and burrowing of female sand fleas (Tunga spp.; Siphonaptera: Tungidae) in the skin of mammals. There are few case reports of severe tungiasis in goats and in these cases the Tunga species were not in most cases clearly identified. Two cases of severe tungiasis caused by Tunga penetrans in goat kids from tungiasis-endemic rural Uganda are reported. These are the first severe cases of tungiasis in goats reported from outside South America.     

Morphological and molecular identification of <Emphasis Type="Italic">Fusarium</Emphasis> species associated with head blight on wheat in East Croatia

Fusarium head blight (FHB) is an important fungal disease of wheat. The aim of this research was to determine the diversity of Fusarium species infecting winter wheat ears in East Croatia. In 2008 wheat kernels were obtained from three locations in the eastern part of Croatia (Tovarnik, Osijek, Pozega), and in 2009 from two additional locations (Slavonski Brod, Nova Gradiska). In total, 498 visually diseased kernels were selected for morphological identification of Fusarium spp. The identity of 226 selected isolates was further investigated by molecular techniques. The predominant species on wheat kernels in East Croatia in 2008 were F. graminearum, isolated and confirmed from more than 80% of sampled wheat kernels, followed by F. avenaceum (8%) and F. culmorum (7%). Incidence of F. poae was less than 2%. The most common species identified in 2009 were F. graminearum (50%), F. culmorum (13%), F. avenaceum (12%) and F. poae (7%). This is the first report on the identification of Fusarium species isolated from naturally infected wheat ears in Croatia.     

Temporal and spatial changes of chlorophyll fluorescence as a basis for early and precise detection of leaf rust and powdery mildew infections in wheat leaves

Temporal and spatial changes in parameters of fast chlorophyll fluorescence kinetics (ground fluorescence, Fo and maximal fluorescence, Fm) and red/NIR reflectance were assessed with a Pulse-Amplitude-Modulated (PAM)-Imaging system on a daily basis over a period of 2 weeks following inoculation of wheat leaves with powdery mildew and leaf rust. The early detection of these infections by means of fluorescence imaging was possible 2–3 days before visual symptoms or significant changes in normalised-differenced-vegetation index (NDVI) became apparent. The initial infection of both fungi caused an increase in Fo and decrease in photochemical efficiency (Fv/Fm, Fv/Fo). The appearance and development of fungal pustules was accompanied by reduction in Fo and Fm. This resulted mainly from lower absorption of fluorescence exciting light by the leaf mesophyll due to the shielding effect of fungal mycelium, and to lesser extent from the chlorophyll breakdown underneath pustules. Among the evaluated fluorescence parameters, Fv/Fo displayed the most pronounced response to both kinds of infection. Mildew infection influenced chlorophyll fluorescence neither in the direct vicinity of mycelium nor in the apparently healthy leaf regions. Rust infected plants, in contrast, displayed significantly reduced photochemical efficiency Fv/Fm and Fv/Fo in chlorotic tissue around pustules. The same, but less pronounced tendency was found in the apparently healthy regions of rust infected leaves in the last days of the experiment. Dark adaptation of leaves proved to be necessary for accurate detection of both pathogen infections by means of fluorescence imaging. Additional experiments are needed to estimate the potential of this technique for remote sensing under field conditions.     

Modulation of some estrogen-responsive genes in the vena cava of ovariectomised Wistar rats by griffonianone C, an isoflavone derived from Millettia griffoniana Baill. (Fabaceae)

In the present study, we investigated whether griffonianone C (Griff C), extracted from root bark of Millettia griffoniana, changes the expression of several estrogen-responsive genes in the vena cava of ovariectomised rats. For this purpose, we subcutaneously administered Griff C (2, 10, or 20 mg/kg/d BW), 17β-estradiol (E2: 10 μg/kg/d BW) as positive control, and a vehicle control respectively for three days. Relative expression levels of estrogen receptor α (ERα), progesterone receptor (PR), cyclooxygenase2 (Cox-2), vascular endothelial growth factor (VEGF), VEGF-receptor 2, angiotensin converting enzyme (ACE), endothelial NO synthase (eNOS), proliferating cell nuclear antigen (PCNA) and Ki67 mRNA extracted from the vena cava of these rats were quantified by real-time PCR. Results showed that Griff C up-regulated the expression of PR, ACE, ERα, VEGF, VEGFR2 and Ki67. However, the results of Cox-2, PCNA, and eNOS expression did not reach significance in the E2 and Griff C treated samples. These results show that griffonianone C regulated a few of the analysed genes in a similar fashion than estradiol; however, others showed a different pattern. This suggests that some of the biological effects attributed to M. griffoniana are mediated via ER pathway others may be mediated via other pathways.     

The variability between different analytical procedures and laboratories for measuring soil microbial biomass C and biomass N by the fumigation extraction method

The interlaboratory variations in the fumigation extraction method and the analytical procedures for measuring C and N in the soil microbial biomass were tested with one soil sample, and two soil extracts (non-fumigated and fumigated) sent to 25 different laboratories. Four groups of analytical procedures for organic C, i.e. (1) oven oxidation/ IR detection, (2) UV-persulfate oxidation/lR detection, (3) UV-persulfate oxidation/colorimetric detection and (4) dichromate oxidation/ titration, and three groups for total N, i.e. (1) Kjedahl reduction to NH₄⁺, (2) UV-persulfate and (3) persulfate-borate oxidation to NO₃^? were used by the different laboratories. The coefficient of variation for C and N measurements between different laboratories and analytical procedures varied between 15 and 34% in non-fumigated samples, between 13 and 20% in fumigated samples, and between 12 and 24% in the differences E_c and E_N. The average coefficients of variation between the replicate measurements within one laboratory were much smaller, i.e. they varied between 3.0 and 9.2% in non-fumigated samples, between 2.4 and 5.5% in fumigated samples, and between 4.5 and 12.8% in the differences E_c and E_n. Extraction and fumigation were not the major source of the variations observed. They were mainly a result of differences in the analytical procedures used to measure the low concentrations of C and N in the extracts. However, all of these analytical procedures should be able to measure correct values if they are properly calibrated and performed.