Implementation of an artificial reaction control in a TaqMan method for PCR detection of <Emphasis Type="Italic">Ralstonia solanacearum</Emphasis> race 3 biovar 2

A previously published TaqMan PCR test for R. solanacearum race 3 biovar 2 was modified to enable both the validation of negative results and the confirmation of positive results in a closed-tube system. Negative results were validated through the use of a reaction control plasmid, designated pRB2C2, which was designed to generate a 94bp product using the same amplimers targeting the primary diagnostic 68bp sequence in R. solanacearum race 3 biovar 2 DNA. SYBR Green was included in the reaction mix to facilitate the identification of post-reaction products using melt peak analysis. The 94bp reaction control had a melt peak temperature of about 90°C, while the diagnostic target amplicon had a melt peak temperature of about 83°C; thus positive results could be easily confirmed and distinguished from the reaction control product. Addition of pRB2C2 at 100 copies per reaction had no effect on the sensitivity of the TaqMan assay for R. solanacearum race 3 biovar 2, and the modified assay successfully detected R. solanacearum race 3 biovar 2 in infected, asymptomatic tomato stems and leaves as well as in potato tubers and stems.     

Understanding Family Forest Land Future Ownership and Use: Exploring Conservation Bequest Motivations

Due to an aging landowner population, there will be an unprecedented ownership shift in land-based assets in the USA. Approximately 2.7 million family forest owners (FFOs) in the USA over the age of 55 years old, reflecting 80 % of all FFO-owned land, will be deciding the future ownership and use of their land, having significant implications for the landscapes and public benefits these forests provide. Little is known about how FFOs plan for the future ownership and use of their land. This study draws from life-cycle theory and FFO decision cycle research to propose a future ownership and use decision-making framework and to explore the presence of and motivation for FFOs to make “conservation bequests” designed to maintain land in its current, forested form. Qualitative interviews with professionals working with over 1000 FFOs explore what triggers FFOs to consider their options and influence their decisions. Findings suggest triggers are universally-held (e.g. age, health) and can happen any time in an FFO’s life. FFO decisions are complex and often made in the context of family goals and dynamics. FFOs holding deep attachments to their land may be more likely to make conservation bequests. However, despite conservation preferences, due to the complex nature of the process or external influences, decisions may not always lead to conservation bequests. The framework that this study adopts allows future in-depth research on these critical decisions. In particular, additional research with landowners is required to examine the framework in more detail.     

Soil soluble organic carbon and nitrogen pools under mono- and mixed species forest ecosystems in subtropical China

Purpose  

The objective of the present study was to assess the differences in soil total C and N, microbial biomass C and N, soil soluble organic C and N among eight mono- and mixed species forest ecosystems (18-year-old restoration) in subtropical China.     

Influence of iron plaque on accumulation of lead by yellow flag (<Emphasis Type="Italic">Iris pseudacorus</Emphasis> L.) grown in artificial Pb-contaminated soil

Purpose  

The relationship between plant absorption and accumulation of heavy metals and the effect of iron plaque on roots of wetland plants are unknown, especially for plants grown in heavy metal-contaminated soil. This experiment was designed to study the effects of iron addition on the formation of iron plaque in the rhizosphere of the wetland plant species Iris pseudacorus L. in artificial Pb-contaminated soil and the effects of iron plaque on Pb accumulation by plants.     

Land Application Effects of a High-Calcium,Dry Flue Gas Desulfurization By-Product on Trace Elements in Runoff from Natural Rainfall

Due to low cost and large abundance, coal continues to be one of the major energy sources for electricity generation in the USA. The dry desulfurization of flue gases during coal combustion produces a by-product that may be potentially useful as a soil amendment. However, the influence of dry flue gas desulfurization (DFGD) by-products on trace element losses with runoff from treated fields has not been well investigated. The objective of this study was to evaluate the effects of land application of a high-Ca, DFGD by-product on trace elements lost in runoff from natural rainfall events. The by-product was applied once on May 18, 2015 at 9 Mg DFGD ha^?1 to small plots of a highly weathered Ultisol under managed-grassland land use in northwest Arkansas. Runoff was collected following each runoff-producing precipitation event for 1 year. Seasonal (i.e., summer (May to August), fall (August to November), winter (November to February), and spring (February to May)) runoff, annual runoff, runoff pH, and electrical conductivity did not differ significantly between DFGD treatments. Seasonal flow-weighted mean Ni concentrations and seasonal V loads were significantly greater in runoff when amended versus the unamended control when compared during at least one 3-month season by 44.5 and 86.9% for Ni and V, respectively. Based on the results of this study, it appears that land application of a high-Ca DFGD by-product at rates ≤?9 Mg ha^?1 has minimal effects on trace elements in runoff.     

Behaviors of Organic and Heavy Metallic Pollutants during Supercritical Water Oxidation of Oil-Based Drill Cuttings

Oil-based drill cuttings (OBDCs), which contain various petroleum hydrocarbons, heavy metals, and alkaline salts, will significantly affect the local ecosystem if left untreated. Supercritical water oxidation (SCWO) is regarded as a potential end-of-pipe technology that is able to degrade organic compounds, stabilize heavy metals, and neutralize alkaline salts simultaneously. In this paper, SCWO of OBDCs was carried out using a batch reactor. Six organic compounds and eight elements were selected as representatives of the petroleum hydrocarbons and heavy metals, respectively, in OBDCs. The effects of the oxygen coefficient (OC), temperature (T), and reaction time (t) on the degradation of petroleum hydrocarbons and the stabilization of heavy metals were evaluated in detail. The results indicated that nearly 100% of naphthalenes and more than 97% of alkanes could be destroyed when T?>?475 °C, t?>?2 min, and OC?>?2.5. The elements Ba, Cr, and Pb were almost completely stabilized in the solid products, and small amounts of Zn and Cu were detected in the liquid products. More than the original contents of Fe, Cr, and Ni were found in the solid products due to the corrosion of the SCWO reactor. The content of alkaline salt in the feed was too low to affect the pH of the liquid products. The results of X-ray diffractometer (XRD) and scanning electron microscope (SEM) analyses suggested that SCWO can efficiently remove organic pollutants from OBDCs but does not obviously affect the microstructure and composition of the inorganic compounds.     

Using a wheat-rye amphihaploid population to map a rye gene responsible for dwarfness

Gene identification in cross-pollinating plants such as rye can be arduous and time consuming because of the difficulties involved with genetic population construction. Here, we provide an alternative approach for the construction of mapping populations to rapidly map genes in cross-pollinated cereal rye. The aim of the present experiments was to genetically analyze the dwarf stature expressed by a germplasm accession of rye. The dwarf phenotype was reversible when the seedlings were exposed to gibberellic acid; the reductions in plant height occurred via reductions in cell size. A mapping population was constructed by generating a set of wheat-rye amphihaploids bred from a single rye plant heterozygous for the dwarfing gene(s). The dwarfness phenotype was expressed in the amphihaploid background, and segregation in the mapping population was consistent with the presence of a single gene. Using rye SSR markers, the gene responsible was located on chromosome arm 1RL, which is also the location of the known rye dwarfing gene Ddw3. This gene is valuable for dwarf breeding of wheat as well as rye.     

An appreciation of the contribution of Frank Stevenson to the advancement of studies of soil organic matter and humic substances

Purpose

The aims of this paper are to outline the state of knowledge with regard to the chemistry of soil organic matter (SOM) prior to 1950; then, to review and evaluate the contributions made by Frank Stevenson during Stevenson’s research period (1950–1994); and subsequently to outline advances that are being made in the modern era.

Progress in the Stevenson period

Frank Stevenson’s research career began in the middle of the twentieth century when a number of techniques of colloid chemistry were available to him, but relatively few of the recently developed instrumental techniques and other procedures of analytical organic chemistry that have enabled significant advances to be made in the chemistry and properties of SOM components.The contributions that Frank Stevenson has made to the chemistry of SOM and of humic substances (HSs) are an integral part of his book (first and second editions) Humus Chemistry: Genesis, Composition, Reactions. The validity of the terms humus and HSs are being questioned as legitimate terms that describe definable components, and SOM is being viewed as a ‘continuum of progressively decomposing organic compounds’. The legitimacy of isolating the organic matter components from their native soil environment is questioned. Those who pose such questions would do well to consider how progress could have been made in the vital life sciences areas of, for example, proteomics and genomics, without the isolation of the relevant cellular components. We recognise the importance of clear and rigorous definitions of HS components and stress the need to isolate these components from the SOM matrix as a prerequisite to the study of the composition, structure and reactivity of these components. We disagree with proposals or suggestions that do not recognise HSs as a scientific entity, and we feel sure that Frank Stevenson would have supported this stance. Various studies of SOM and of HSs have taken place over the centuries, but progress was slow because the tools required to study such complex systems were not available. Frank Stevenson’s research involved many areas of humic chemistry, and his major advances were in aspects of functionality and in the interactions of humic functional groups with metals and to a lesser extent with anthropogenic organic chemicals. His studies of nitrogen and of ammonia in relation to organic matter also had a very great impact.

Progress in the modern era

Frank Stevenson can be said to have provided the stimulation that enabled beginners and established scientists to obtain a good grasp of the fundamentals of SOM and the humic sciences. His scientific contributions have catalysed many of the significant advances that have been made in the field since he retired. In the final section, some of the advances that have been made using modern analytical techniques are addressed and some of the controversial topics that have recently arisen are discussed.