Genetic diversity and population structure of Raffaelea quercus‐mongolicae,a fungus associated with oak mortality in South Korea

Raffaelea quercus‐mongolicae is a fungus associated with oak wilt and deemed to cause extensive oak mortality in South Korea. Since the discovery of this fungus on a dead Mongolian oak (Quercus mongolica) in 2004, the mortality continued to spread southwards in South Korea. Despite continued expansion of the disease and associated significant impacts on forest ecosystems, information is lacking about the origin and genetic diversity of R. quercus‐mongolicae. Restriction‐site‐associated DNA (RAD) sequencing was used to assess genetic diversity and population structure among five populations (provinces) of R. quercus‐mongolicae in South Korea. In total, 179 single nucleotide polymorphisms (SNPs) were identified among 2,639 RAD loci across the nuclear genome of the 54 R. quercus‐mongolicae isolates (0.0012 SNPs per bp), which displayed an overall low expected heterozygosity and no apparent population structure. The low genetic diversity and no apparent population structure among South Korean populations of this ambrosia beetle‐vectored fungus support the hypothesis that this fungus was introduced to South Korea.     

Evaluation of Antioxidant,Lipid, and Protein Fractions of Accessions of Oryza Species

The genus Oryza has given rise to rice (Oryza sativa L.), a major source of food for much of the human population. The Oryza genus is small, including only 23 species, but it is remarkably diverse in terms of its ecological adaptation. This diversity may not be only restricted to ecological characteristics but also to kernel end‐use quality characteristics. This study was undertaken to evaluate Oryza species as a gene pool for improving the properties of rice bran for human consumption. Several accessions of 13 Oryza species were grown in a greenhouse, along with eight rice (Oryza sativa L.) accessions displaying low and high bran oil content, as well as low and high palmitic acid content. The total lipid content of the Oryza species was within the range found for Oryza sativa accessions. However, the level of palmitic acid in the O. species was as high as that reported for soybean high‐palmitic acid mutants. Oryza species also contained higher levels of the γ‐oryzanol and phenolic fractions compared to cultivated rice. Low or not significant phenotypic correlations between lipid, palmitic acid, and γ‐oryzanol suggest that these fractions in cultivated rice could be increased simultaneously using several of the Oryza species accessions identified in this study. A cultivar with enhanced levels of these fractions would be suitable for use in the production of high γ‐oryzanol margarine, shortening, and frying oils.     

A novel conceptual framework for long‐term leaching of autochthonous soil particles during transient flow

To date, most of the experimental and modelling research on the mobilization mechanisms of autochthonous colloidal‐sized soil particles has focused on single rainfall events. However, in the field, natural events interrupted by rainless periods of various durations follow one another. Some studies have shown that the amount of leached particles is much affected by the chronology of rainfall events. In this paper, we propose a model to compute the amount of mobilized particles during the transient flow regime of long series of successive rainfall events. Particles that can be mobilized are assumed to be located at the surface of preferential flow paths in contact with flowing water. As water passes, particles are mobilized, thus uncovering new particles and renewing the stock of mobilizable particles. We also report experimental data on the impact of long series of rainfall events on particle mobilization in undisturbed calcareous soil columns under controlled conditions. The model provides a framework to understand the variation of mobilization observed during the transient flow regime of these rainfall events. These variations resulted in part from the interplay between macropore water content at the onset of rain and the chronology of previous rainfall events. Additionally, the model provides a feedback loop between particle mobilization and minute macropore structure modifications. Once coupled with a particle transport model this feature may be useful to model soil structure changes during long series of successive rainfall events.     

Explaining Rice Milling Quality Variation Using Historical Weather Data Analysis

Rice quality, specifically head rice yield (HRY), can vary inexplicably from one lot to another, and from year to year. In an effort to correlate air temperatures during various growth stages to HRY, growth staging data expressed in degree day units was used to predict the occurrence of sequential growth stages within a set of 17‐year historical data, which included HRY and 50% heading dates for two long‐grain rice cultivars, (Oryza sativa L) Newbonnet and Lemont, and area weather data. HRY was most strongly affected by the average daily low temperature (or nighttime temperature) during the R8 developmental stage. Lower HRY were associated with high nighttime air temperatures during this stage for both Newbonnet and Lemont. When used as a single variable in a regression model, the nighttime temperature during the R8 developmental stage explained over 25% of the variation in HRY.     

Trends in relief design and construction in opencast mining reclamation

This paper examines trends in topography design and construction in opencast mining restoration. The greatest geomorphological focus is the protection of aquatic ecosystems downstream of reclaimed sites through the construction of topographies and structures that not only reduce sediments and contaminants to a minimum, but which soften the impact of maximum water flows. From the ecological point of view, the most important focus is the integration of the geomorphological component with those of the soil and vegetation, and the formation of a functional ecosystem with the capacity to maintain itself. The conceptual models of relief that have been used in practice are discussed and criticized: these include the platform‐bank model (geotechnically but not ecologically stable), faithful reproduction of the original topography (inadequate in steep areas), and understanding the hydrological basin as a restoration unit (now considered the most appropriate). Finally, erosion models are reviewed as tools for relief design. The practicality of ‘RUSLE 1.06 for Mined Lands, Construction Sites and Reclaimed Lands’ is underlined owing to its ease of use. Copyright © 2003 John Wiley & Sons, Ltd.     

Changes during winter in water‐stable aggregation due to crop residue quality

There is a need to develop practices that contribute to increased water‐stable aggregation (WSA) during winter in a humid temperate climate when soil is particularly prone to water erosion. Our objectives were to determine the effects of crop residue quality on WSA during winter and to relate these effects to biochemical indicators of fungal and bacterial biomass. Three graminae crop residues were selected for their different C/N ratios and biochemical characteristics (green oat residues, C/N = 18.8; wheat straw, C/N = 125.6; and mature miscanthus residues, C/N = 311.3). In October 2009, crop residues were added with an equivalent amount of C in the 0–10 cm layer to a Luvisol in north‐west France. WSA, expressed as mean weight diameter (MWD), amino sugar, soil mineral N and water contents were measured at regular intervals during 5 months. Aggregate MWD of the control soil decreased rapidly and remained low until the last sampling date in March which illustrates the structural vulnerability of bare soils in winter in this pedo‐climatic area. The incorporation of all three crop residues had significant positive impacts on aggregate MWD. Despite widely different C/N ratios, the maximum MWD under each treatment was similar (three times greater than the control soil). Maximum MWD occurred at times that clearly depended on residue quality. Maximum values occurred early for green oat (29 day), but were delayed to 50 day for wheat straw and to 154 day for miscanthus. Results from correlation analysis suggest that variations in WSA were partly mediated by microbial agents with a dominant effect of bacteria for green oat and a combined role of fungal and bacterial biomass for wheat straw. We suggest that the maximum MWD associated with the miscanthus late in the experiment is related to changes in the composition of the fungal community. Overall, our study shows that autumn application of crop residues increases WSA during winter with its effect being microbially mediated and determined by residue quality.     

Soil organic‐C accumulation and N availability under improved pastures established in Mediterranean oak woodlands

Long‐term effects of improved pasture establishment (with high proportion of legumes) on soil organic‐C status and N availability in Mediterranean cork oak (Quercus suber L.) woodlands were assessed. Soils were sampled beneath scattered crowns and in open areas, considering two systems: unmanaged and managed woodlands where improved pastures were installed 26 and 32 years ago. Total and labile C and N pools were measured and C and N mineralization were determined over 24 weeks laboratory incubation. Soils under improved pastures showed higher organic‐C, total‐N and net N mineralization than those under unmanaged pasture, mainly when established beneath trees. Potentially mineralizable C, C mineralization rate and microbial C were not statistically different between the unmanaged and improved pasture sites, but were higher closer to the tree than in the open area (1.8, 1.2 and 1.2 times, respectively). The qCO₂ was higher in improved pastures (1.7 times). Labile pool of C and N extracted with hot water increased under improved pasture (3.4 and 1.7 times, respectively). Results indicate that soil quality amelioration by improved pastures is stronger in the presence of oak trees. Management systems that favour oak tree maintenance and regeneration should be taken into account to reverse soil degradation.     

The rice soils of Cambodia. II. Statistical discrimination of soil properties by the Cambodian Agronomic Soil Classification system (CASC)

Abstract. A novel agronomic system of soil classification for managing rice soils in Cambodia (CASC) was developed recently. It integrates local knowledge about the soil with its conceptual and taxonomic understanding by soil scientists. Using quantitative soil survey data we evaluated the agronomic efficacy of the classification system. Although the CASC is based on simple field criteria it explained 25 to 44% of the variation in soil prop-erties relevant for agronomic decision making. It failed, however, to differentiate soil types based on pH (6% of variances explained). Despite its simplicity it performed as well or better than the most widely used soil map in Cambodia (Crocker, 1962), and unlike this small-scale soil map it allows classification on a field-specific basis. The average values of soil properties were often significantly different between groups. Organic carbon, clay content and plant available magnesium and calcium contributed most to the discrimination of CASC soil groups. The predictive accuracy when allocating new samples on the basis of quantitative survey data to soil groups of the CASC was 50% to 100%, except for soil groups Kein Svay (0%) and Kampong Siem (20%). The CASC is valuable for managing Cambodian rice soils and may also be used for up-scaling and mapping of soil information.     

Effects of Temperature,Sonication Time,and Power Settings on Size Distribution and Extractability of Total Wheat Flour Proteins as Determined by Size‐Exclusion High‐Performance Liquid Chromatography

The size‐exclusion (SE) HPLC profile of total protein extract obtained by sonication of flour samples at ambient temperature showed marked instability on reinjection. Instability was related to the presence of flour proteases that were inactivated by thermal treatment of flour samples at 60°C. Extraction of flour protein by sonication was a function of ultrasonic energy (sonication time × power product) delivered to flour sample. As protein solubility increased, the proportions of the earliest eluted SE‐HPLC fractions (F1 and F2) increased. Oversonication of proteins evidenced by a decrease in F1 amount at the benefit of F2 occurred below the sonication energy level needed for total protein extraction. Ultrasonic energy level was adjusted to allow total protein extraction while limiting oversonication. The sonication procedure was applied on 27 flour samples of contrasting dough strength to extract total proteins. Absolute amount of protein extractable by sonication, determined from SE‐HPLC area, was strongly correlated with flour protein content. Very significant and equivalent relationships were found between alveographic W index and absolute amount of either unextractable protein extract or F1 of SE‐HPLC profile from total protein extract.