Can the extent of degradation of soil fungal mycelium during soil incubation be used to estimate ectomycorrhizal biomass in soil?

The extent of degradation of the fungal biomass in forest soil during laboratory incubation was investigated as a measure of ectomycorrhizal (EM) biomass. The method simulates the disappearance of fungal mycelium after root trenching, where the EM fungi, deprived of its energy source (the tree), will start to die off. Incubating a forest humus soil at 25 °C resulted in a decrease in the relative proportion (mol%) of the phospholipid fatty acid 18:2ω6,9 (a fungal marker molecule) within 3-6 months, indicating that fungal biomass was disappearing. Incubation at 5 °C resulted in essentially no change in the amount of 18:2ω6,9. The measurement of ergosterol, another fungal marker molecule, gave similar results. Incubation of different forest soils (pine, spruce and spruce/oak), and assuming that the disappearance of fungal biomass during this period of time was entirely due to EM fungi, resulted in an estimation of EM biomass of between 47 and 84% of the total fungal biomass in these soils. The humus layer had more EM biomass than deeper mineral layers.     

Influence of oxygen on production and consumption of nitric oxide in soil

Summary NO and N₂O release rates were measured in an acidic forest soil (pH 4.0) and a slightly alkaline agricultural soil (pH 7.8), which were incubated at different O₂ concentrations (<0.01 – 20% O₂) and at different NO concentrations (40 – 1000 ppbv NO). The system allowed the determination of simultaneously operating NO production rates and NO uptake rate constants, and the calculation of a NO compensation concentration. Both NO production and NO consumption decreased with increasing O₂. NO consumption decreased to a smaller extent than NO production, so that the NO compensation concentrations also decreased. However, the NO compensation concentrations were not low enough for the soils to become a net sink for atmospheric NO. The release of N₂O increased relative to NO release when the gases were allowed to accumulate instead of being flushed out. The forest soil contained only denitrifying, but not nitrifying bacteria, whereas the agricultural soil contained both. Nevertheless, NO release rates were less sensitive to O₂ in the forest soil compared to the agricultural soil.     

High-performance liquid chromatography (HPLC) analysis of phenolic compounds in berries with diode array and electrospray ionization mass spectrometric (MS) detection: ribes species

High-performance liquid chromatography combined with diode array and electrospray ionization mass spectrometric (MS) detection was used to study phenolic compounds in berries of black, green, red, and white currants (Ribes spp.). UV-visible spectrometry was a valuable tool for the identification of the class of the phenolic compound, whereas MS and MS-MS fragmentation data were useful for further structural characterization. Distinct similarities were found in the relative distribution of conjugated forms of phenolic compounds among the four currants. Phenolic acids were found mainly as hexose esters. Flavonol glycosides and anthocyanin pigments were mainly found as 3-O-rutinosides and second as 3-O-glucosides. However, cyanidin 3-O-sambubioside and quercetin hexoside-malonate were notable phenolic compounds in red currant. Flavonol hexoside-malonates were identified and quantified in the berries of currants for the first time.     

Structural characterization of oligosaccharides and polysaccharides from apple juices produced by enzymatic pomace liquefaction

Eight apple pomace liquefaction juices were produced to characterize soluble cell wall material released by the action of pectolytic and cellulolytic enzyme preparations. Very high colloid values from 9.7 to 19.6 g/L were recovered from the juices by ethanol precipitation. The crude polysaccharides consisted mainly of galacturonic acid (49-64 mol %), arabinose (14-23 mol %), galactose (6-15 mol %), and minor amounts of rhamnose, xylose, and glucose. Separation of the polysaccharides by anion-exchange chromatography yielded one neutral, one slightly acidic, and one acidic polymer accounting for 60% of total colloids. Preparative size exclusion chromatography of the acidic fractions resulted in four polymers of different molecular weights and different sugar compositions. Among them, high molecular weight arabinans and rhamnogalacturonans as well as oligomeric fractions consisting of only galacturonic acid could be found. Linkage studies were performed on neutral fractions from anion-exchange chromatography and size exclusion chromatography. They revealed highly branched arabinans, xyloglucans, and mainly type I arabinogalactans.     

Validation of the two-gene epistatic model for vernalization response in a winter × spring barley cross

A two gene epistatic model in which a dominant “winter growth habit” allele at Vrn-H2 encodes a repressor with a corresponding binding site in a recessive vrn-H1 allele explains the vernalization response phenotypes in an array of barley germplasm. In order to validate the model genetically, we developed an F ₂ population (and F ₂-derived F ₃ families) from the cross of Hardy (winter) × Jubilant (spring). Using gene-specific primers, we determined the Vrn-H1 and Vrn-H2 allele architecture of each F ₂ plant and we measured the growth habit phenotype of each F ₂ plant via phenotyping of its F ₃ progeny under controlled environment conditions. We used a set of treatments involving plus/minus vernalization under long photoperiod and vernalization under short photoperiod. Alleles at the two loci showed expected patterns of segregation and independent assortment. Under long day conditions, the two Vrn genes were the primary determinants of heading date, regardless of the vernalization treatment. Under short photoperiod, the effects of these loci were not significant. There was incomplete dominance at Vrn-H1: heterozygotes were significantly later to head than Vrn-H1Vrn-H1 genotypes. Vrn-H2 genotypes were also significantly later to head, even when plants were vernalized. These results validate the two-gene epistatic model for vernalization response under long-day conditions. The results under short photoperiod, and the variance in flowering with vernalization, confirm that while the two Vrn genes are the primary determinants of vernalization response, they are part of a larger interactome that determines the timing of the vegetative to reproductive transition.     

Agronomic performance of crosses between Nordic and exotic barleys

Exotic germplasm may be useful for the improvement of agronomic performance of barley breeding material. This study was conducted in order 1) to evaluate if it is possible to improve performance of Nordic barley breeding material by utilizing exotic germplasm sources (unadapted landraces and H. spontaneum), 2) to evaluate incorporation of exotic germplasm into a genetic base widely adapted to the agro-ecological conditions of the extreme Scandinavian north as well as to the base adapted to the conditions of the south of this geographical region, and 3) to evaluate whether an index composed of several traits corresponded to 'breeder's phenotypic evaluation' of the progenies. Earliness, straw length, number of ears/plant, yield/plant, seed shattering, persistence of awns and an index computed from these traits were studied in Swedish and Finnish 4-way crosses along with their adapted parents. Most of the crosses headed earlier than their adapted parents and none of the crosses outyielded the adapted parents. The most favorable frequency distributions for the index were found in the crosses with only cultivated barleys as parents. Transgressive segregates were also found in progenies with H. spontaneum parents. Incorporation of exotic barleys was most successful into the local genetic base. Comparisons between indices and breeder's phenotypic evaluation suggested reconsideration of evaluation methods early in parent development.     

Exotic barley germplasm: variation and effects on agronomic traits in complex crosses

Summary Utilization of exotic germplasm offers an approach to broaden genetic variability in breeding populations. This study was conducted in order to 1) compare germplasm of exotic origin with adapted Swedish barleys with respect to genetic differences and 2) to evaluate how exotic material affected agronomic performance in complex crosses. Allozyme studies showed the following Nei's gene diversities among parents: 0.13 (adapted parents), 0.16 (landraces) and 0.25 (H. spontaneum). Cluster analysis indicated that parental groups were genetically divergent. Earliness, straw length, number of ears per plant and thousand kernel weight (TKW) were studied. Variation in agronomic traits showed the following pattern: landraces > H. spontaneum > adapted lines. The best sources for earliness were adapted parents and landraces. Mean straw length was greatest in H. spontaneum lines. Number of ears per plant was quite similar in all groups. The highest TKW was among landraces and adapted parents. Hybrids from the complex crossing programme exceeded parents in earliness and TKW. An index composed from the four traits showed the most favorable frequency distributions for adapted parents and hybrids. Both genetic and agronomic studies indicate that new valuable variation from exotic germplasm may be introduced into barley breeding material.