Some fluorine-containing pheromone analogues

Two analogues of the aphid alarm pheromone (E)-β-farnesene, a trifluorofarnesene and a difluoro-1-norfarnesene, were found to be highly active and were more readily detectable than the parent compound. For (Z)-hexadec-11-enal, a component of some lepidopteran sex attractant pheromones, replacement of the carbonyl oxygen with a difluoromethyl group to give a difluoroheptadecadiene resulted in loss of activity. A trifluoroacetoxyhexadecanolide was a more volatile analogue of the mosquito oviposition pheromone (?)-(5R,6S)-6-acetoxy-5-hexadecanolide and was highly active.     

Using ground-penetrating radar to detect layers in a sandy field soil

Pollutant transport in sandy soils can be very complex due to the presence of coarse sand lenses. Water flows laterally over the coarse material and, subsequently, breakthrough occurs in concentrated pathways, called fingers. This (funneled) flow process is a form of preferential flow reducing solute travel time and degradation of organic chemicals.

In this paper, we test ground-penetrating radar (GPR) as a tool for detecting layers in the soil. Several GPR transects were established on a fine sandy loam soil throughout the growing season and subsequent fall period to find the best time to reveal layer structures. The effect of the spatially varying moisture content on the radar velocity was determined from actual measurements with soil samples and by using the Common Mid-Point (CMP) technique. The optimal time to find coarse layers with GPR in this soil was at the end of the fall season when the soil was wetted and evaporation had decreased. The depth of layers, as indicated by GPR, was highly sensitive to the soil moisture content and could be in error by as much as ±0.4 m on a depth scale of 1.5 to 2 m if an average propagation velocity was used. A satisfactory depth prediction of textural interfaces was obtained non-destructively by collecting data in both reflection and CMP mode.     

Engineering for disease resistance: persistent obstacles clouding tangible opportunities

The accelerating pace of gene discovery, coupled with novel plant breeding technologies, provides tangible opportunities with which to engineer disease resistance into agricultural and horticultural crops. This is especially the case for potato, wheat, apple and banana, which are afflicted with fungal and bacterial diseases that impact significantly on each crop's economic viability. Yet public scepticism and burdensome regulatory systems remain the two primary obstacles preventing the translation of research discoveries into cultivars of agronomic value. In this perspective review, the potential to address these issues is explained, and specific opportunities arising from recent genomics‐based initiatives are highlighted as clear examples of what can be achieved in respect of developing disease resistance in crop species. There is an urgent need to tackle the challenge of agrichemical dependency in current crop production systems, and, while engineering for disease resistance is possible, it is not the sole solution and should not be proclaimed as so. Instead, all systems must be given due consideration, with none dismissed in the absence of science‐based support, thereby ensuring that future cropping systems have the necessary advantage over those pathogens that continue to inflict losses year after year. © 2014 Society of Chemical Industry     

Animal treading stimulates denitrification in soil under pasture

The effects of animal treading on denitrification in a mixed ryegrass-clover pasture were studied. A single treading event of moderate or severe intensity was applied in plots during spring by using dairy cows at varying stocking rates (4.5 cows 100 m⁻² for 1.5 or 2.5 h, respectively). Treading caused a significant short-term 21 days) increase in denitrification. Denitrification rates reached a maximum of 52 g N₂O-N ha⁻¹ day⁻¹ at 8 days after severe treading compared to 2.3 g N₂O-N ha⁻¹ day⁻¹ under nil treading. Thereafter, denitrification rates declined, and were similar to non-trodden control plots after 28 days. Soil aeration, was significantly reduced by treading as expressed by water-filled porosity. In addition, soil NH₄⁺-N and NO₃⁻-N concentrations were also increased by treading. We propose that the underlying processes involved in increasing denitrification under treading were two-fold. Firstly, treading caused a temporary (e.g. 3 days after treading) reduction in soil aeration through soil physical damage, and secondly, reduced soil N utilisation prompted by reduced plant growth led to increased soil NH₄⁺-N and NO₃⁻-N availability. This study shows that treading, without the influence of other grazing animal factors (e.g. excretion), can cause a large short-term stimulation of denitrification in grass-clover pastures.     

The internet-based fungal pathogen database: a proposed model

ABSTRACT A better understanding of the phenotypic and genetic diversity of significant agricultural pathogens and how their populations change in the field is critical for designing successful, long-term disease management strategies. Although efforts to determine the genetic diversity of plant pathogens have substantially increased in recent years, mainly due to the availability of various molecular tools, complementary efforts to archive and integrate the resulting data have been very limited. As a consequence, it is often difficult to compare the available data from various laboratories because the data have been generated by diverse tools, often preventing any direct comparisons, and are saved in a format that is unsuitable for comparative studies. The establishment of an internet-based database that cross-links the digitized genotypic and phenotypic information of individual pathogens at both the species and population levels may allow us to effectively address these problems by coordinating the generation of data and its subsequent archiving. We discuss the needs, benefits, and potential structure of such a database.