Spatial heterogeneity,incidence-incidence and incidence-lesion density relationship of apple scab (<Emphasis Type="Italic">Venturia inaequalis</Emphasis>) in managed orchards

The spatial pattern of apple scab was characterized using 10 years of disease incidence and lesion density data collected in managed orchards located in Quebec, Canada. Distributional analyses indicated that scab incidence was better characterized by the beta-binomial than the binomial distribution in 53 and 65% of the data sets at the leaf and shoot scales, respectively. Median values of the beta-binomial parameter θ, a measure of small-scale aggregation, were near 0 (0.003 and 0.028) at both sampling scales, indicating that disease incidence was close to being randomly distributed (low degree of aggregation). For lesion density, the negative binomial distribution fitted the data better than the Poisson distribution in 86% of the data sets at the leaf scale. The median value of the index of dispersion k was 0.068, indicating that aggregation was present. For all apple scab measurements, the power law models provided a good fit to the data. The estimated slope and intercept parameters were significantly greater than 1 and 0, respectively, suggesting that spatial heterogeneity changed systematically with disease incidence. Results of a covariance analysis showed that spatial heterogeneity of scab incidence at both scales and lesion density was not dependent upon shoot type but that spatial heterogeneity of scab incidence and lesion density at the leaf scale was influenced by the sampling period. A hierarchical analysis showed that scab incidence at the tree scale increased as a saturation-type curve with respect to incidence at the leaf or shoot scales. A similar relationship was observed for incidences at the shoot and leaf scales. An effective sample size model based on the binary power law parameters (Madden and Hughes, Phytopathology 89:770–781, 1999) gave the best fit to the leaf and shoot data, respectively. The incidence-lesion density relationship at both scales was well described by a complementary log-log (CLL) and log transformation model ( R_adj² = 0.97 and R_adj² = 0.94 ) \left( {R_{{adj}}^2 = 0.97\,and\,R_{{adj}}^2 = 0.94} \right) , however, the models tended to underestimate lesion density. The information of the spatial relations of apple scab within and between hierarchical scales acquired from this study can be used in developing and evaluating practical disease management strategies and to improve apple scab assessments for fungicide or cultivar susceptibility trials.     

Mechanisms of resistance to fungicides in field strains of Botrytis cinerea

Field strains of Botrytis cinerea Pers ex Fr, the causal agent of grey mould diseases, were collected from French vineyards between 1993 and 2000. Several phenotypes have been characterized according to the inhibitory effects of fungicides towards germ-tube elongation and mycelial growth. Two types of benzimidazole-resistant strains (Ben R1 and Ben R2) could be detected; negative cross-resistance to phenylcarbamates (e.g. diethofencarb) was only found in Ben R1. Benzimidazole resistance was related to point mutations at codon 198 (Ben R1) or 200 (Ben R2) of the beta-tubulin gene. Most dicarboximide-resistant strains were also weakly resistant to aromatic hydrocarbon fungicides (e.g. dicloran) but remained sensitive to phenylpyrroles (e.g. fludioxonil). These resistant field strains (Imi R1) contained a single base pair mutation at position 365 in a two-component histidine kinase gene, probably involved in the fungal osmoregulation. Three anilinopyrimidine-resistant phenotypes have been identified. In the most resistant one (Ani R1), resistance was restricted to anilinopyrimidines, but no differences were observed in the amino-acid sequences of cystathionine beta-lyase (the potential target site of these fungicides) from Ani R1 or wild-type strains. In the two other phenotypes (Ani R2 and Ani R3), resistance extended to various other groups of fungicide, including dicarboximides, phenylpyrroles and sterol biosynthesis inhibitors. This multi-drug resistance was probably determined by over-production of ATP-binding cassette transporters. The hydroxyanilide fenhexamid is a novel botryticide whose primary target site is the 3-keto reductase involved in sterol C-4 demethylations. Apart from the multi-drug-resistant strain Ani R3, three other fenhexamid-resistant phenotypes have been recognized. For two of them (Hyd R1 and Hyd R2) fenhexamid-resistance seemed to result from P450-mediated detoxification. Reduced sensitivity of the target site could be the putative resistance mechanism operating in the third resistant phenotype (Hyd R3). Increased sensitivity to inhibitors of sterol 14 alpha-demethylase recorded in Hyd R1 strains was related to two amino-acid changes at positions 15 and 105 of this enzyme.     

Host species barriers to influenza virus infections

Most emerging infectious diseases in humans originate from animal reservoirs; to contain and eradicate these diseases we need to understand how and why some pathogens become capable of crossing host species barriers. Influenza virus illustrates the interaction of factors that limit the transmission and subsequent establishment of an infection in a novel host species. Influenza species barriers can be categorized into virus-host interactions occurring within individuals and host-host interactions, either within or between species, that affect transmission between individuals. Viral evolution can help surmount species barriers, principally by affecting virus-host interactions; however, evolving the capability for sustained transmission in a new host species represents a major adaptive challenge because the number of mutations required is often large.     

The global impact of scaling up HIV/AIDS prevention programs in low- and middle-income countries

A strong, global commitment to expanded prevention programs targeted at sexual transmission and transmission among injecting drug users, started now, could avert 28 million new HIV infections between 2005 and 2015. This figure is more than half of the new infections that might otherwise occur during that period in 125 low- and middle-income countries. Although preventing these new infections would require investing about U.S.$122 billion over this period, it would reduce future needs for treatment and care. Our analysis suggests that it will cost about U.S.$3900 to prevent each new infection, but that this will produce a savings of U.S.$4700 in forgone treatment and care costs. Thus, greater spending on prevention now would not only prevent more than half the new infections that would occur from 2005 to 2015 but would actually produce a net financial saving as future costs for treatment and care are averted.     

Fertigation rate,leaching fraction,and growth of potted poinsettia

Single‐pinched poinsettia (Euphorbia pulcherrima ’V‐14 Glory') in 15‐cm pots received constant fertigation with 50, 100, 200, and 300 mg.L^‐1 nitrogen (N) from a 20N‐4.4 phosphorus (P)‐16.6 potassium (K) fertilizer with a leaching fraction (LF) of 0, 0.2, or 0.4. Plants received 25 irrigations during the 13‐week study. The shoot fresh and dry masses with 50, 100, and 300 mg.L^‐1 N at the 0.4 LF were 30% larger than at the 0 LF. The 300 mg.L^‐1 N fertigated plants had approximately 15% more leaf area and almost 122% more bract area than the 50 mg.L^‐1 N fertigated plants. The leaf N concentration of plants fertigated with 100, 200, and 300 mg.L^‐1 N was near or in the normal range of 4 to 6%, but was below the critical level of 3.5% with 50 mg.L^‐1 N fertigation. In contrast, the leaf P concentration approached or exceeded the toxic level of 0.9% with 100 to 300 mg.L^‐1 N. The N fertigation of 100 to 200 mg.L^‐1 is adequate for producing a quality poinsettia crop. Quality poinsettias can be grown at a 0 LF if quality irrigation water is available. With 11 mg.L^‐1 P via fertigation, the leaf P concentration was in the acceptable range. The P concentration in the 20N‐4.4P‐16.6K complete fertilizer was excessive for poinsettia and would contribute to unnecessary P leaching.     

Polar constituents from the aerial parts of Origanum vulgare L. Ssp. hirtum growing wild in Greece

From the polar extracts of Origanum vulgare L. ssp. hirtum 19 compounds have been isolated. The structures and relative stereochemistry have been elucidated by spectroscopic analysis and determined as apigenin, luteolin, chrysoeriol, diosmetin, quercetin, eriodictyol, cosmoside, vicenin-2, caffeic acid, p-menth-3-ene-1,2-diol 1-O-beta-glucopyranoside, thymoquinol 2-O-beta-glucopyranoside, thymoquinol 5-O-beta-glucopyranoside, thymoquinol 2,5-O-beta-diglucopyranoside, 12-hydroxyjasmonic acid, 12-hydroxyjasmonic acid 12-O-beta-glucopyranoside, lithospermic acid B, rosmarinic acid, 10-epi-lithospermic acid, and epi-lithospermic acid B. The three latter products display unusual stereochemistry of the 3,4-hydroxyphenyllactic acid unit(s), which to the authors' best knowledge has never been reported before in similar compounds. Moreover, lithospermic acid B (and its stereoisomers), p-menth-3-ene-1,2-diol 1-O-beta-glucopyranoside, 12-hydroxyjasmonic acid, and 12-hydroxyjasmonic acid 12-O-beta-glucopyranoside were isolated for the first time from Origanum species.     

Effects of increased nitrogen supply on the lignification of poplar wood

The short-term influence of adequate and high nitrogen fertilization on poplar lignification was investigated. The high nitrogen supply decreased lignin staining in the newly formed secondary xylem, indicating that lignin deposition was affected. Acetyl bromide determinations gave a 9-10% decrease in lignin content; however, Klason lignin content was unchanged. Thioacidolysis showed that elevated N supply affected lignin structure such that there was a reduced frequency of lignin units involved in beta-O-4 bonds, a reduced syringyl/guaiacyl ratio, an increased frequency of p-hydroxyphenyl lignin units, more guaiacyl units with free phenolic groups, and more p-hydroxybenzoic acid ester-linked to poplar lignins. These features suggest that lignins from poplars grown under high N bear structural similarities to lignins formed during early stages of wood development. The findings also indicate that a gravitational stimulus inducing the formation of tension wood and high N availability lead to similar and additive effects on lignin content and structure.     

Using transgenic poplars to elucidate the relationship between the structure and the thermal properties of lignins

In an attempt to draw relationships between the molecular structure and the thermal behavior of lignins, thermomechanical analyses were run on six milled wood and enzyme poplar lignin fractions prepared from genetically modified and control woods. All the lignin samples displayed similar thermal profiles with a clear inflection point assigned to the glass transition point. The temperature (T(g)) at which this transition occurs showed large variations from 170 to 190 degrees C, depending both on the genetic modification and on the age of the tree. These variations were found to be closely related to the condensation degree of lignins evaluated by thioacidolysis.     

A morphological approach to understanding preferential flow using image analysis with dye tracers and X-ray Computed Tomography

A key problem facing soil physics and hydropedology at present is some of the standard theories of water flow in soils do not fully reflect the processes at the pore scale, and thus, cannot be adequately used for prediction. As such, examination of soil structure is vital for hydropedologists. Realisation that solutes move preferentially through soil into groundwaters has meant research in this area has increased in importance. This paper describes a multi-scale approach to analyse transport mechanisms using visualisation techniques. Chloride and Brilliant Blue tracers were applied to undisturbed soil cores to examine the physical and morphological properties associated with preferential flow in a range of soil types. Following collection of serial digital images, it was possible to examine and quantify the nature of active water flow mechanisms in terms of both dye-stained pathways and spatial distribution of dye concentration, using image analysis. Preferential flow linked to water potential and soil structural discontinuity was observed in all but the coarsest textured soil which conformed to uniform flow theory. A high level of variability in flow patterns was noted between the soil types. Such information as to how a soil dynamically re-wets is key for hydropedologists involved in applications such as pollution modelling. This is especially significant when considering a wetting mechanism, such as preferential flow, that cannot be adequately described by conventional soil physics.