Salmonella Brandenburg--emergence of a variant strain on a sheep farm in the South Island of New Zealand

Salmonella Brandenburg was initially diagnosed in New Zealand in an aborted ewe from a Merino flock in mid-Canterbury in1996. The following year, the disease occurred on farms in mid-Canterbury and on one farm near Winton in Southland (Bailey1997). Since then, this bacterium has caused widespread abortion and deaths in pregnant ewes in Southland, coastal Otago and south- and mid-Canterbury. In cattle, the same organism has caused diarrhoea and dysentery in calves and adult cattle, and abortions and deaths in first-calving cows and, to a lesser extent, in second-calving and older cows. Salmonella Brandenburg has also caused diarrhoea and fetal deaths in dogs, and diarrhoea and deaths in foals. The outbreak strain has been extensively studied using pulsed-field gel electrophoresis (PFGE). All isolates tested to date have had an indistinguishable molecular pattern with the exception of a single isolate from a sheep-yard dust sample recovered in October 2000 that is the subject of this report. The molecular pattern of the variant strain differed from that of the epidemic strain by the absence of one high molecular weight band and the addition of three lower molecular weight bands.     

The challenges of maintaining wheat productivity: pests, diseases, and potential epidemics

Knowing pests and diseases that may cause injuries and are likely to affect plant health and quality is critical to minimizing the gap between attainable yield and actual yield. In this paper, we highlight concepts and strategies aimed at controlling major biotic constraints affecting wheat in intensive production systems and present emerging challenges, with a special attention to the developing world. Disease epidemics result from the combination of inoculum, favorable environment, and host susceptibility. Changes in cropping systems as a result of adoption of conservation agriculture may have serious implications. Necrotrophic pathogens such as those responsible for tan spot or septorias are likely to emerge, and Fusarium head blight may increase. However, resistance breeding combined with rotations, timely sowing, and irrigation or even fungicide utilization, if affordable, are part of integrated crop management practices that can minimize losses. In South Asia, the effect of spot blotch, a devastating foliar disease caused by Cochliobolus sativus, can be minimized by reducing physiological stress through timely sowing and adequate use of fertilizers, which demonstrates the complex relationships among crop physiology, disease resistance, and yield. Although some root rots that induce premature death of tillers in cooler high-yielding humid environments can be important, the dryland crown rot (Fusarium spp.), common root rot (C. sativus), and the cereal nematode (Heterodera spp. and Pratylenchus spp.) should not be ignored. These are all known to be much more damaging under suboptimal moisture (rainfed or supplementary irrigation), particularly where plant growth is stressed. Climate change is likely to modify the wheat disease spectrum in some regions, and pathogens or pests considered unimportant today may turn out to be potential new threats in future.     

Accumulation of Zn, Cd, Cu, and Pb in Chinese cabbage as influenced by climatic conditions under protected cultivation

Accumulation of heavy metals from agricultural soils contaminated by low levels heavy metals has important implications in the understanding of heavy metal contamination in the food chain. Through field experiments (1994-1996), the influence of thermal regime under different treatments on the accumulation of zinc, cadmium, copper, and lead in Chinese cabbage [Brassica pekinensis (Lour) Rupr. cv. Nagaoka 50] grown in a Calcareous Fluvisol (Xerofluvent) in Granada (southern Spain) was examined. Two floating row covers were used: T(1) (perforated polyethylene, 50 microm thick) and T(2) (17 g m(-2) polypropylene nonwoven fleece). An uncovered cultivation (T(0)) served as control. Zn, Cd, Cu, and Pb levels in the whole tops of experimental plants were analyzed. Treatments T(1) and T(2) gave rise to differences in environmental conditions with respect to T(0). The influence of environmental factors manipulated by floating row covers (particularly under T(1)) increased total heavy metal accumulation in the above ground plant biomass with respect to the open-air crop. The total contents of Zn, Cd, Cu, and Pb were 30, 50, 90, and 40% higher in T(1), respectively, than in T(0). This technique could be used in contaminated zones for different plant species because the thermal effect favors the process of phytoextraction and thus reduces the contamination.     

Using high resolution UAV thermal imagery to assess the variability in the water status of five fruit tree species within a commercial orchard

This paper deals with the assessment of heterogeneity in water status in a commercial orchard, as a prerequisite for precision irrigation management. Remote sensing-derived indicators could be suitable for mapping water stress over large areas, and recent studies have demonstrated that high resolution airborne thermal imagery enables the assessment of discontinuous canopies as pure tree crowns can be targeted, thus eliminating the background effects. Airborne campaigns were conducted over a drip-irrigated commercial orchard in Southwestern Spain composed of five different orchard tree crops. An unmanned aerial vehicle with a thermal camera onboard was flown three times during the day on 8 July 2010, at 9, 11 and 13 h (local time). Stem water potential was measured at the same time of the flights. In some irrigation units, irrigation was stopped prior to the measurement date to induce water deficits for comparative purposes. Several approaches for using the thermal data were proposed. Daily evolution of the differential between canopy and air temperature (T _c  ? T _a ) was compared to tree water status. The slope of the evolution of T _c  ? T _a with time was well correlated with water status and is proposed as a novel indicator linked with the stomatal behavior. The Crop Water Stress Index (CWSI) was calculated with the temperature data from the 13.00 h flight using an empirical approach for defining the upper and lower limits of T _c  ? T _a . The assessment of variability in water status was also performed using differences in relative canopy temperatures. Ample variability was detected among and within irrigation units, demonstrating that the approach proposed was viable for precision irrigation management. The assessment led to the identification of water-stressed areas, and to the definition of threshold CWSI values and associated risks. Such thresholds may be used by growers for irrigation management based on crop developmental stages and economic considerations.     

The Effect of the Organic Matter Composition on POP Accumulation in Soil

The effect of different humic fractions on polychlorinated biphenyl (PCB) contamination in soils was tested in the field by means of 53 soil samples from a high-altitude grassland plateau in the Italian Alps. Three humic fractions (humin, humic acids, and fulvic acids) were characterized in parallel by quantifying 12 PCB congeners to establish a direct relationship between PCB levels and humic fraction concentrations. Humin (the most hydrophobic fraction) appears to be the most closely correlated with the amount of PCBs in soil (R ²?=?0.83), while fulvic acid shows the lowest correlation (R ²?=?0.49). The idea of preferential sorption of hydrophobic compounds in the humin fraction is discussed, and the humin carbon content (f _huminC) is proposed as an improved parameter for evaluating the potential for POP accumulation in soils, replacing total organic carbon (f _oc). Congener studies revealed that penta- and hexa-substituted-CBs show the optimal combination of physicochemical properties for equilibrating with the humin content in soil. Moreover, f _huminC/f _oc is conceptually equivalent to the empirical coefficients used in predictive K _sa equations. In our samples, the f _huminC/f _oc was 0.55, a value in between the empirical coefficients proposed in the literature. In predictive equations, the use of f _huminC instead f _oc avoids the necessity of using an empirical parameter for a ??generic?? condition by introducing an experimental parameter (f _huminC) that takes into account local conditions (organic matter composition).     

Identification and characterization of genes differentially expressed in cherimoya (Annona cherimola Mill) after exposure to chilling injury conditions

Cherimoyas (Annona cherimola), like other subtropical/tropical fruits, are susceptible to damage from exposure to temperatures between 0 and 5 °C (chilling injury, CI), which may affect fruit quality. To increase our understanding of the molecular mechanisms involved in the CI response, a forward suppression subtractive hybridization (SSH) cDNA library was constructed. In this work, we obtained 75 genes that could potentially be involved in the CI response. The CI induced activation of genes that are involved in a range of metabolic pathways, such as primary metabolism, transport, and endomembrane traffic, among others. We also characterized the expression of 12 selected genes in different A. cherimola tissues by polymerase chain reaction (PCR), and we confirmed the differential expression of a subset in CI fruits by real-time quantitative PCR (qPCR). The expression of six A. cherimola genes: annexin (AcAnex), UDP-glucose pyrophosphorylase (AcUGP), syntaxin of plants 71 (AcSyp71), 1-aminocyclopropane-1-carboxylic-acid synthase (AcACS), ubiquitin carrier-like protein (AcUCP), and enolase (AcEnol), was up-regulated after cold storage for 12 days at 0 °C. These results imply that selected genes could be related to the development of internal browning observed in cherimoyas after exposure to CI conditions. The information generated in this study provides new clues that may aid in understanding the cherimoya ripening process.     

A MODIFIED CAPACITANCE PROBE TECHNIQUE FOR ESTIMATING PASTURE YIELD

An instrument for estimating pasture yield electronically was constructed. It was a modification of that described by Campbell et al (1). A transistorized crystal oscillator was incorporated to provide a highly stable frequency standard for use in the field. This provided a zero reference point for both the measuring head oscillator and the reading oscillator before and during use. The instrument is fully described and details are given of its field adjustment and operation.