樟疫多聚半乳糖醛酸酶Pcpg 1、Pcpg 2和Pcpg 4基因的克隆、测序及其遗传转化

研究优化了樟疫(Phytophthora cinnamomi)多聚半乳糖醛酸酶Pcpg1、Pcpg2和Pcpg4基因克隆的PCR条件，并对其进行了克隆、测序和遗传转化。克隆获得了3个基因，其大小均为1011bp；通过构建表达载体和遗传转化获得了3个基因的转基因菌系；3个基因均能指导合成相应的PG酶，其中转化Pcpg2基因的酵母菌(Saccharomyces cewvisiae)所分泌的多聚半乳糖醛酸酶(PG)酶活性最强，Pcpg4和对照Anpg(Aspergillus niger polygalacturonase)1次之，而Pcpg1基因所指导合成的PG酶无活性。Western blotting表明，所克隆的3个基因所指导合成的PG酶均有不同程度的糖基化。     

Sub-obliterative effects of mine-tailing on marine infaunal benthos

The effect of mine-tailing on benthic productivity in a threshold inlet was explored by studies on the polychaete Ammotrypane aulogaster Rathke, 1843. Ammotrypane was chosen as an indicator species of potentially reduced production in the area fringing total benthic obliteration due to its abundance (up to 1017 m^?2) at the time of the surveys. Densities, weights and lengths were inversely related to greater tailing deposition. These observations indicate that under light tailing there is some loss in benthic production. More detailed time-series studies are now required to measure the extent of the loss.     

Evaluation of pheromone release from commercial mating disruption dispensers

Pome fruit growers and crop consultants have expressed concerns about the seasonal release performance of commercial codling moth mating disruption dispenser products. Because of these concerns, we developed a laboratory flow-through volatile collection system (VCS) for measuring the volatile release of the codling moth sex pheromone, codlemone, from commercially available hand-applied dispensers. Under controlled air-flow and temperature conditions, the released vapor was trapped onto a polyurethane foam adsorbent followed by solvent extraction, solvent reduction, and GC/MS determination. Method recovery and breakthrough validations were performed to demonstrate system reliability before determining codlemone release from commercial dispensers field-aged over 140 days. The volatile collection was carried out in a consistent manner among five dispenser types most commonly used by growers, so that direct comparison of performance could be made. The comparison showed differences in the amount of pheromone released and in the patterns of release throughout the season between dispenser types. The variation in release performance demonstrates the need for routine evaluation of commercially marketed mating disruption dispensers. We believe that the simple and cost-effective volatile collection system can assist pheromone dispenser manufacturers in determining seasonal dispenser performance before new products are introduced into the commercial market and in rapidly verifying dispenser release when field-aged dispenser efficacy is in question.     

Dissolved organic nitrogen uptake by plants—an important N uptake pathway?

The direct uptake of dissolved organic nitrogen (DON) by plants has the potential to be a primary Factor in ecosystem functioning and vegetation succession particularly in N-limiting environments. Clear experimental evidence to support this view, however, is still lacking. Further, many of the experimental approaches used to assess whether DON is important may be compromised due to the use of inappropriate methods for comparing and quantifying plant available inorganic and organic soil N pools. In addition, experiments aimed at quantifying plant DON capture using dual-labelled (¹⁵N, ¹³C) organic N tracers often do not consider important aspects such as isotope pool dilution, differences in organic and inorganic N pool turnover times, bi-directional DON flows at the soil-root interface, and the differential fate of the ¹⁵N and ¹³C in the tracer compounds. Based upon experimental evidence, we hypothesize that DON uptake from the soil may not contribute largely to N acquisition by plants but may instead be primarily involved in the recapture of DON previously lost during root exudation. We conclude that while root uptake of amino acids in intact form has been shown, evidence demonstrating this as a major plant N acquisition pathway is still lacking.     

Carbon sequestration in a temperate grassland; management and climatic controls

Soil management practices that result in increased soil carbon (C) sequestration can make a valuable contribution to reducing the increase in atmospheric CO₂ concentrations. We studied the effect of poultry manure, cattle slurry, sewage sludge, NH₄NO₃ or urea on C cycling and sequestration in silage grass production. Soil respiration, net ecosystem exchange (NEE) and methane (CH₄) fluxes were measured with chambers, and soil samples were analysed for total C and dissolved organic C (DOC). Treatments were applied over 2 years and measurements were carried out over 3 years to assess possible residual effects. Organic fertilizer applications increased CO₂ loss through soil respiration but also enhanced soil C storage compared with mineral fertilizer. Cumulative soil respiration rates were highest in poultry manure treatments with 13.7 t C ha^?1 in 2003, corresponding to 1.6 times the control value, but no residual effect was seen. Soil respiration showed an exponential increase with temperature, and a bimodal relationship with soil moisture. The greatest NEE was observed on urea treatments (with a CO₂ uptake of ?4.4 g CO₂ m^?2 h^?1). Total C and DOC were significantly greater in manure treatments in the soil surface (0–10 cm). Of the C added in the manures, 27% of that in the sewage pellets, 32% of that in the cattle slurry and 39% of that in the poultry manure remained in the 0–10 cm soil layer at the end of the experiment. Mineral fertilizer treatments had only small C sequestration rates, although uncertainties were high. Expressed as global warming potentials, the benefits of increased C sequestration on poultry manure and sewage pellet treatments were outweighed by the additional losses of N₂O, particularly in the wet year 2002. Methane was emitted only for 2–3 days on cattle slurry treatments, but the magnitudes of fluxes were negligible compared with C losses by soil respiration.     

Modeling yield sustainability for different rotations in long-term barley trials

In crop rotation trials, the errors arising over time on the same plot are correlated. Often-used analyses assume zero or constant correlation between the errors while the actual covariance structure for the plot errors might be very different. The objective of this study was to identify the most suitable covariance structure and incorporate the error structure in assessment of the crop rotations in terms of yield productivity and yield sustainability. A set of five covariance structures were examined for barley yield data from a 14-year, two-course barley rotation trial conducted at two locations in northern Syria. Selection of the covariance structures was based on the Akaike information criterion (AIC, Akaike 1974) (a function of penalized log-likelihood) obtained from fitting the structure. Covariance structure with heterogeneous variances and with constant correlation between errors over cycles within the same plot was found to account for most variability in grain and straw yields at both locations. Modeling data with this covariance structure, the legume rotations gave higher productivity as well as higher annual increases compared with the continuous barley system. This implies that an agricultural production system based on a legume following a cereal is likely to be more sustainable for cereal production compared to cereal followed by cereals.     

High salt tolerance potential in Lycopersicon species during germination

Summary The potential to improve seed germination responses to salinity was evaluated for 13 accessions representing six wild Lycopersicon species and 20 accessions of L. esculentum. Germination response times increased in all accessions at 100 mM NaCl. Analysis indicated that one accession of L. peruvianum (PI126435) germinated faster under high salinity than all other accessions and was closely followed by L. pennellii (LA716). The fastest germinating L. esculentum accession, PI174263, ranked third. Additional wild ecotypes exhibiting rapid germination at 100 mM NaCl were identified among L. pimpinellifolium and L. peruvianum.     

The addition of a pair of chromosomes of the wild oat Avena barbata (2n=28) to the cultivated oat A. sativa L. (2n=42)

Summary The chromosome of A. barbata on which the gene controlling mildew resistance is located, has been added to the complement of the cultivated oat A. sativa. The breeding behaviour of the chromosome addition line is not sufficiently stable to allow the development of cultivars based on these aneuploid lines. However, the monotelocentric addition line involving only the appropriate arm of the barbata chromosome offers distinct possibilities for the development of oat cultivars incorporating the mildew resistance of A. barbata.