Host density dependence and environmental factors affecting laurel wilt disease incidence

Host size, density, and distribution, in addition to climate, can affect the likelihood a pathogen will invade and saturate landscapes. Laurel wilt, caused by the vector-borne pathogen Raffaelea lauricola, has devastated populations of native Lauraceae in the south-eastern USA, and continues to spread. We surveyed 87 plots in six coastal islands in South Carolina, Georgia, and north Florida, and one inland site (Archbold Biological Station) in south Florida for laurel wilt-affected and unaffected individual plants belonging to the genus Persea. The coastal island sites were surveyed once in 2008 or 2009, and the inland site was surveyed eight times from 2011 to 2013. Disease incidence per plot ranged from 0% to 96%, with mean disease incidence 42% across all sites. Disease incidence was positively correlated with trunk diameter and with density of hosts with trunk diameter >5 cm, but negatively correlated with the degree of clustering, which was highest for small trees. A recursive partitioning model indicated that higher disease incidence was associated with moderate temperatures, wider trunk diameter, lower relative humidity, and lower wind speeds. Disease progress over time at Archbold followed a Gompertz curve, plateauing at 3% in 2 years. The dispersal kernel for disease incidence from a focus followed a negative exponential distribution. The number of plots with diseased trees at Archbold was similar for redbay (P. borbonia) and swampbay (P. palustris) but was lower for silkbay (P. humilis). Understanding how host density, size, and diversity interact with environmental effects will help guide future risk prediction efforts.     

Prevalence of contagious mastitis pathogens in bulk tank milk in Prince Edward Island

The purpose of this study was to 1) estimate the herd prevalence of contagious mastitis pathogens in bulk milk from Prince Edward Island (PEI) dairy farms, 2) determine the association between bulk milk culture results and mean bulk milk somatic cell count (BMSCC), and 3) investigate the agreement of repeated bulk milk cultures. Three consecutive bulk milk samples were obtained at weekly intervals from all 258 PEI dairy herds and were cultured using routine laboratory methods. Cumulative prevalence of Staphylococcus aureus, Streptococcus agalactiae, and Mycoplasma spp. (M. bovis and M. alkalescens) was 74%, 1.6%, and 1.9%, respectively. Bulk milk somatic cell count of Staph. aureus-positive herds was higher than that of negative herds. Agreement for Staph. aureus isolation between 3 consecutive tests was moderate (kappa = 0.46). Mycoplasma bovis and M. alkalescens in bulk milk are being reported for the 1st time in PEI ever and in Canada since 1972.     

Cacao diseases: important threats to chocolate production worldwide

ABSTRACT Theobroma cacao, cacao, is an ancient, neotropical domesticate. It is now grown throughout the humid, lowland tropics and is the basis of a multibillion dollar confectionary trade. Diverse diseases impact production of the crop. They reduce yields by ca. 20%, but could cause far greater losses if certain highly damaging diseases were to become more widely distributed. Among the most potentially dangerous of these diseases are frosty pod, caused by Moniliophthora roreri, and witches' broom, caused by M. perniciosa (previously Crinipellis perniciosa). These two diseases occur only in the Western Hemisphere, and severe losses would follow their introduction to West Africa and Asia, where ca. 86% of all cacao production occurs. Elsewhere, Cacao swollen shoot virus and the damaging black pod agent, Phytophthora megakarya, are found in Western Africa; whereas vascular streak dieback, caused by Oncobasidium theobromae, is present only in Asia. Breeding programs are challenged by minimal resistance to some of the diseases. Progress that has been made is threatened by the "emergence" of other serious diseases, such as Ceratocystis wilt (Ceratocystis cacaofunesta). During this symposium, new insights are discussed on the biology, origins, pathology and phylogeny of the pathogens; as well as the biological, chemical and genetic management of the diseases that they cause.     

Widespread genetic switches and toxicity resistance proteins for fluoride

Most riboswitches are metabolite-binding RNA structures located in bacterial messenger RNAs where they control gene expression. We have discovered a riboswitch class in many bacterial and archaeal species whose members are selectively triggered by fluoride but reject other small anions, including chloride. These fluoride riboswitches activate expression of genes that encode putative fluoride transporters, enzymes that are known to be inhibited by fluoride, and additional proteins of unknown function. Our findings indicate that most organisms are naturally exposed to toxic levels of fluoride and that many species use fluoride-sensing RNAs to control the expression of proteins that alleviate the deleterious effects of this anion.     

Tolerance and accumulation of shikimic acid in response to glyphosate applications in glyphosate-resistant and nonglyphosate-resistant cotton (Gossypium hirsutum L.).

Measurement of shikimic acid accumulation in response to glyphosate inhibition of 5-enolpyruvylshikimate-3-phosphate synthase is a rapid and accurate assay to quantify glyphosate-induced damage in sensitive plants. Two methods of assaying shikimic acid, a spectrophotometric and a high-performance liquid chromatography (HPLC) method, were compared for their accuracy of recovering known amounts of shikimic acid spiked into plant samples. The HPLC method recovered essentially 100% of shikimic acid as compared with only 73% using the spectrophotometric method. Relative sensitivity to glyphosate was measured in glyphosate-resistant (GR) and non-GR cotton leaves, fruiting branches, and squares (floral buds) by assaying shikimic acid. Accumulation of shikimic acid was not observed in any tissue, either GR or non-GR, at rates of 5 mM glyphosate or less applied to leaves. All tissues of non-GR plants accumulated shikimic acid in response to glyphosate treatment; however, only fruiting branches and squares of GR plants accumulated a slight amount of shikimic acid. In non-GR cotton, fruiting branches and squares accumulated 18 and 11 times, respectively, more shikimic acid per micromolar of translocated glyphosate than leaf tissue, suggesting increased sensitivity to glyphosate of reproductive tissue over vegetative tissue. GR cotton leaves treated with 80 mM of glyphosate accumulated 57 times less shikimic acid per micromolar of translocated glyphosate than non-GR cotton but only 12.4- and 4-fold less in fruiting branches and squares, respectively. The increased sensitivity of reproductive structures to glyphosate inhibition may be due to a higher demand for shikimate pathway products and may provide an explanation for reports of fruit abortion from glyphosate-treated GR cotton.     

Nutrition and the burden of disease in New Zealand: 1997-2011

OBJECTIVE: To estimate the burden of disease due to selected nutrition-related risk factors (high total blood cholesterol, high systolic blood pressure, high body mass index (BMI) and inadequate vegetable and fruit intake) in 1997, as well as the burden that could potentially be avoided in 2011 if small, favourable changes in the current risk factor distribution were to occur. DESIGN: Data on risk factor levels, disease burden and risk associations were combined using comparative risk assessment methodology, a systematic approach to estimating both attributable and avoidable burden of disease. Disease outcomes assessed varied according to risk factor and included ischaemic heart disease, stroke, type 2 diabetes mellitus and selected cancers. SETTING: New Zealand. RESULTS: Approximately 4500 deaths (17% of all deaths) in 1997 were attributable to high cholesterol, 3500 (13%) to high blood pressure, 3000 (11%) to high BMI and 1500 (6%) to inadequate vegetable and fruit intake. Taking prevalence overlap into account, these risk factors were estimated jointly to contribute to approximately 11 000 (40%) deaths annually in New Zealand. Approximately 300 deaths due to each risk factor could potentially be avoided in 2011 if modest changes were made to each risk factor distribution. CONCLUSIONS: High cholesterol, blood pressure and BMI, as well as inadequate vegetable and fruit intake, are major modifiable causes of death in New Zealand. Small changes in the population distribution of these risk factors could have a major impact on population health within a decade.     

Characterization of Cry34Ab1 and Cry35Ab1 insecticidal crystal proteins expressed in transgenic corn plants and Pseudomonas fluorescens

Cry34Ab1 and Cry35Ab1 proteins, identified from Bacillus thuringiensis strain PS149B1, act together to control corn rootworms. Transgenic corn lines coexpressing the two proteins were developed to protect corn against rootworm damage. Large quantities of the two proteins were needed to conduct studies required for assessing the safety of this transgenic corn crop. Because it was technically infeasible to obtain sufficient quantities of high purity Cry34Ab1 and Cry35Ab1 proteins from the transgenic corn plants, the proteins were produced using a recombinant Pseudomonas fluorescens (Pf) production system. The two proteins from both the transgenic corn and the Pf were purified and characterized. The proteins from each host had the expected molecular mass and were immunoreactive to specific antibodies in enzyme-linked immunosorbent assay and Western blot analysis. Data from N-terminal sequencing, tryptic peptide mass fingerprinting, internal peptide sequencing, and biological activity provided direct evidence that the Cry34Ab1 and Cry35Ab1 proteins produced in Pf and transgenic corn were, respectively, comparable or equivalent molecules. In addition, neither protein had detectable glycosylation regardless of the host.     

Testing for trends when there are changes in methods

Data from monitoring projects often include sampling or analytical changes that preclude trend analysis on the entire period of record. A modification of the nonparametric Kendall's test for monotonic trends, which accounts for such changes in the period of record, is described here. This approach blocks the data so that only data collected or analyzed under similar circumstances are compared. Alternatively, when appropriate data exist, data collected using the old method may be calibrated to values expected from the new method. Traditional trend tests may then be applied to resulting data sets. Results from simulations assessing both the power of the blocked test and the standard test performed on calibrated data are presented. The power of the blocked test exceeded the power of the calibration approach only when the calibration error was extremely large. Both the blocking and calibration approaches were applied to and compared for chemical data from Vermont lakes.     

How much is enough? Landscape-scale conservation for the Florida panther

The Florida panther (Puma concolor coryi) is an endangered, wide-ranging predator whose habitat needs conflict with a rapidly growing human population. Our goal was to identify specific regions of the south Florida landscape that are of high conservation value to support a self-sustaining panther population. We used compositional and Euclidean distance analyses to determine relative importance of various land cover types as panther habitat and to investigate the role of forest patch size in habitat selection. A model of landscape components important to Florida panther habitat conservation was created. The model was used in combination with radio telemetry records, home range overlaps, land use/land cover data, and satellite imagery to delineate Primary and Secondary zones that would comprise a landscape mosaic of cover types sufficient to support a self-sustaining population. The Primary Zone generally supports the present population and is of highest conservation value, while the Secondary Zone is of lesser value but could accommodate expansion of the population given sufficient habitat restoration. Least-cost path models identified important landscape linkages, and model results were used to delineate a Dispersal Zone to accommodate future panther dispersal outside of south Florida. We determined that the three habitat zones could support 80-94 panthers, a population likely to persist and remain stable for 100 years, but that would be subject to continued genetic problems. The Primary, Dispersal and Secondary zones comprise essential components of a landscape-scale conservation plan for the protection of a viable Florida panther population in south Florida. Assessments of potential impacts of developments should strive to achieve no net loss of landscape function or carrying capacity for panthers within the Primary Zone or throughout the present range of the Florida panther.