Sensitivity towards DMI fungicides and haplotypic diversity of their CYP51 target in the Mycosphaerella graminicola population of Flanders

Journal of Plant Diseases and Protection - Septoria leaf blotch, caused by the fungus Mycosphaerella graminicola, is the most important wheat disease in Northwestern Europe, and is currently...     

Invasion of Phytophthora infestans at the landscape level: how do spatial scale and weather modulate the consequences of spatial heterogeneity in host resistance?

Strategic spatial patterning of crop species and cultivars could make agricultural landscapes less vulnerable to plant disease epidemics, but experimentation to explore effective disease-suppressive landscape designs is problematic. Here, we present a realistic, multiscale, spatiotemporal, integrodifference equation model of potato late blight epidemics to determine the relationship between spatial heterogeneity and disease spread, and determine the effectiveness of mixing resistant and susceptible cultivars at different spatial scales under the influence of weather. The model framework comprised a landscape generator, a potato late blight model that includes host and pathogen life cycles and fungicide management at the field scale, and an atmospheric dispersion model that calculates spore dispersal at the landscape scale. Landscapes consisted of one or two distinct potato-growing regions (6.4-by-6.4-km) embedded within a nonhost matrix. The characteristics of fields and growing regions and the separation distance between two growing regions were investigated for their effects on disease incidence, measured as the proportion of fields with ≥1% severity, after inoculation of a single potato grid cell with a low initial level of disease. The most effective spatial strategies for suppressing disease spread in a region were those that reduced the acreage of potato or increased the proportion of a resistant potato cultivar. Clustering potato cultivation in some parts of a region, either by planting in large fields or clustering small fields, enhanced the spread within such a cluster while it delayed spread from one cluster to another; however, the net effect of clustering was an increase in disease at the landscape scale. The planting of mixtures of a resistant and susceptible cultivar was a consistently effective option for creating potato-growing regions that suppressed disease spread. It was more effective to mix susceptible and resistant cultivars within fields than plant some fields entirely with a susceptible cultivar and other fields with a resistant cultivar, at the same ratio of susceptible to resistant potato plants at the landscape level. Separation distances of at least 16 km were needed to completely prevent epidemic spread from one potato-growing region to another. Effects of spatial placement of resistant and susceptible potato cultivars depended strongly on meteorological conditions, indicating that landscape connectivity for the spread of plant disease depends on the particular coincidence between direction of spread, location of fields, distance between the fields, and survival of the spores depending on the weather. Therefore, in the simulation of (airborne) pathogen invasions, it is important to consider the large variability of atmospheric dispersion conditions.     

Dietary L-carnitine supplementation enhances the lipopolysaccharide-induced acute phase protein response in broiler chickens

The objective of the present study was to evaluate the potential effects of dietary L-carnitine supplementation on acute phase protein response upon a lipopolysaccharide (LPS) challenge of male broiler chickens receiving a commercial broiler diet supplemented with 15 or 100 mg L-carnitine/kg or an unsupplemented (control) diet from 14 days of age onwards. At 28 days of age, eight chickens per dietary treatment were weighed and subcutaneously injected with 300 microg LPS from E. coli (100 microg LPS/ml saline) or 3 ml saline (unsupplemented group only). During the next 10 days, blood samples were taken repeatedly and analysed for their hemopexin (HX) and alpha-1 acid glycoprotein (AGP) levels. Extra dietary L-carnitine did not affect broiler performance. At day 1 postinjection, plasma HX and AGP levels were significantly increased in all treatment groups. However, the elevations in circulating HX and AGP levels were more pronounced in the L-carnitine supplemented chickens, especially in the 100mg L-carnitine group. It is concluded that extra L-carnitine in the diet of broiler chickens enhances or advances the acute phase protein response. The exact mode of action needs to be elucidated but seems to be consistent with a glucocorticoid mimicking effect.     

Water erosion assessment using farmers' indicators in the West Usambara Mountains, Tanzania

The contribution of local knowledge to ecological sciences has not been fully exploited: there is still a gap between the recognition of farmers' knowledge as valid and an effective use of such knowledge in activities aimed at sustainable development. This study explores the use of farmers' indicators of erosion for developing a rapid tool for water erosion assessment at field level in the West Usambara Mountains (Tanzania). Two extensive field surveys were conducted in the research area concurrently. One survey consisted of applying an established erosion assessment method, the Assessment of Current Erosion Damage (ACED). According to the erosion features observed, fields were classified into five erosion classes, from very slightly eroded to very severely eroded. The second survey consisted of recording the type and number of indicators of erosion listed by farmers and present in the fields. The number of farmers' indicators per field increased with erosion intensity, from less than four in slightly eroded fields to more than eight in severely eroded fields. All farmers' indicators were positively correlated to the ACED erosion assessment classes. However, two groups of farmers' indicators could be distinguished in terms of erosion assessment: strong indicators, which were observed in more than 70% of cases in severely eroded fields, and weak indicators, which were observed more frequently in slightly and moderately eroded fields. Weak indicators appeared to be indicative of other land degradation phenomena, such as chemical fertility decline. Strong indicators and number of indicators were used to create a field erosion assessment tool in the form of a classification tree. The tree was built using one half of the field survey data and validated using the other half. The tree consisted of a hierarchical sequence of questions. Presence of rills and number of farmers' indicators were the most important factors of the tree. The validation yielded a highly significant Spearman's rho correlation coefficient (0.81). The contingency table showed that more than 80% of very severely eroded fields were correctly classified, whereas most misclassification occurred among slightly and moderately eroded fields. Farmers include land degradation phenomena and soil fertility decline in their definition of soil erosion. Soil and water conservation planning should address this broader farmers' perception by including, e.g., soil fertility improvements beside soil conservation. The distinction between strong and weak indicators of erosion is important in recommending the right intervention in the right spot, e.g., by counteracting soil erosion where strong indicators are present and by improving chemical fertility where weak indicators are present. The classification tree is of empirical nature and may need adaptation before being applied to other areas. The proposed methodology can be easily replicated and showed a high potential to provide extensionists with a field tool for erosion assessment. The classification tree was a successful example of integrating different types of knowledge for enhancing the co-operation between stakeholders involved in the erosion-control activities.     

Evaluation of dry ashing in conjunction with ion chromatographic determination of transition metal ions in pig feed samples

The contents of transition metal ions iron, copper, zinc, and manganese were simultaneously determined in pig feed using an ion chromatographic technique (IC) preceded by dry ashing. Employing ion exchange, the ions were separated on an IonPac CS5A column used in combination with a pyridine-2,6-dicarboxylic acid based eluent. The separation was followed by spectrophotometric detection after postcolumn reaction with 4-(2-pyridylazo)resorcinol. Dry ashing parameters were varied to assess their role in potential analyte loss. Quantitative recoveries (>95%) were obtained for all analytes with a dry ashing method that included a moderate temperature-time regime and ash leaching support in the form of sonication and heat treatment. The use of HCl as leaching acid and the presence of alkaline earths in the matrix solution did not interfere with the chromatographic separation.     

Formation and accumulation of alpha-acids,beta-acids,desmethylxanthohumol, and xanthohumol during flowering of hops (Humulus lupulus L.)

Important secondary metabolites, present in hops (Humulus lupulus L.), include alpha-acids and beta-acids, which are essential for the brewing of beer, as well as the prenylated chalcones, desmethylxanthohumol, and xanthohumol, which exhibit interesting bioactive properties. Their formation and accumulation in five selected hop varieties, Wye Challenger, Wye Target, Golding, Admiral, and Whitbread Golding Variety, were quantitatively monitored by high-performance liquid chromatography using UV detection. All target compounds were present from the onset of flowering, not only in female hop cones but also in male inflorescences, albeit in low concentrations. During development from female inflorescences to cones, levels of alpha-acids, beta-acids, desmethylxanthohumol, and xanthohumol gradually increased, while each hop variety exhibited individual accumulation rates. Furthermore, these compounds were present in leaves of fully grown hops as well. The study demonstrated that key compounds for flavor and potential beneficial health effects associated with beer not only reside in the glandular lupulin structures but also are distributed over various parts of the hop plant.     

Effect of Phosphorus and Arbuscular Mycorrhizal Fungi (AMF) Inoculation on Growth and Productivity of Maize (Zea mays L.) in a Tropical Ferralsol

Soil fertility in the Lubumbashi region often proves to be limiting factor for crop production due to their low nutrient reserves. The objective of this work was to evaluate the impact of arbuscular mycorrhizae on phosphorus uptake by maize on Ferralsol. The trial was conducted in pots with 30?kg or 60?kg of P₂O₅ ha^?1 and a control. These three levels of phosphorus were combined or not with arbuscular mycorrhizae. The combinations of 30?kg or 60?kg of phosphorus with the inoculum led to a male flowering of maize at 63 days after semi. Maize treated with 60?kg of phosphorus ha^?1 formed very few or almost no blisters in the roots. Cob weight, length, diameter, number of rows and kernel weight varied significantly with phosphorus on both inoculated and uninoculated pots. The inoculated plants had high averages for these yield parameters. Due to the lack of phosphate fertilizer, inoculum alone can be an alternative to phosphorus provided that nitrogen and potassium are added, resulting in small but seed-filled ears compared to the phosphorus-free control without mycorrhizae, which resulted in empty ears. Yield varied significantly with the addition of phosphorus (0.3 to 6.1 tons ha^?1) and less significantly with inoculum (3 to 3.7?t ha^?1). The combination of treatments showed a significant difference in favour of the 60?kg of phosphorus or 60?kg of phosphorus associated with the inoculum. The highest phosphorus content was obtained on the inoculum treatment alone, which provided 1.4?mg phosphorus?g^?1 maize compared to other treatments, which provided 0.69 to 0.71?mg phosphorus?g^?1 maize.

     

Exploring genetic diversity and disease response of cultivated rice accessions (<Emphasis Type="Italic">Oryza</Emphasis> spp.) against <Emphasis Type="Italic">Pyricularia oryzae</Emphasis> under rainfed upland conditions in Benin

The main goal of this study is to gain insight into the relationship between the genetic profile of cultivated rice (Oryza spp.) accessions and their resistance to rice blast. Therefore, the genetic and phenotypic variability of a set of 350 cultivated rice accessions originating from Africa (Benin, Mali and Nigeria, Ivory Coast etc.) was examined. Seventy-seven fluorescent amplified fragment polymorphism (AFLP) markers were used to gain insight into the genetic variation and to classify the germplasm collection. In addition, the rice germplasm was assessed for its resistance to blast disease caused by Pyricularia oryzae in upland field conditions. Huge differences in responses of rice accessions to P. oryzae were observed, ranging from highly susceptible to highly resistant. Twelve percent of all accessions were highly resistant to P. oryzae. Based on their AFLP marker profile these highly resistant accessions could be separated from the other accessions. Stepwise regression revealed that the best prediction of the blast resistance level was achieved with a maximum number of 13 AFLP markers. Marker CTA22 was the most important for accurate prediction of blast resistance, this marker was present in all highly resistant accessions. It can be concluded that AFLP markers are a valuable tool to screen rice accessions for their susceptibility towards blast disease and that, based on a subset of markers, it is possible to predict the resistance to rice blast.