Distribution of the airborne inoculum of wheat leaf rust and septoria tritici blotch : impact on epidemics in wheat fields and implications for integrated pest management

Like pollen, spores of pathogenic fungi can take to the air in order to disperse. We have hypothesized that a quantitative analysis of the airborne inoculum of wheat pathogens would lead, first, to a better understanding of the epidemiology of wheat diseases and, second, to an improvement in short-term predictions, as a guide to farmers. Two major foliar diseases of wheat in Belgium were chosen: septoria tritici blotch (STB) and wheat leaf rust (WLR), which differ in propagation, development and survival mechanisms. STB occurs early in the wheat development, mainly through airborne contamination by ascospores, produced by the sexual cycle. Its spread to the upper leaves during wheat development is known to be mainly due to asexual pycnidiospores dispersed by rain splashes. However, airborne inoculum analysis indicated that STB inoculum was present throughout the growing season, with a seasonal pattern. Using mechanistic models, the study showed that contamination of the upper leaves could be better explained by taking account of the airborne inoculum, particularly when asexual reproduction was impeded (e.g., resistant varieties or early fungicide treatments). The detection profiles for WLR, a biotrophic pathogen, indicated the possible existence of a ‘green bridge’, whereby WLR overwinters on the seedlings and volunteers (self-sown) of wheat. It was also shown that the pathogen’s survival from one cropping season to the next one was highly dependent on weather conditions in autumn and winter. Airborne WLR inoculum, however, can be a limiting factor in the development of severe epidemics. The prediction of WLR infection of upper leaves was improved by analyzing the airborne inoculum data or the predicted concentrations at critical points in time. The inclusion of airborne inoculum profiles, as well as weather conditions, in the monitoring of STB and WLR development in the field led to a review of the conditions needed for the upper leaves of wheat to be infected by these two important pathogens. Taking account of airborne inoculum data emerged as an important factor in the choice of fungicide treatments and the application of integrated pest management strategies, which would potentially have important economic and environmental benefits.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 201

L’implication des étudiants dans la formation médicale

Objectifs : Présenter un panorama général des diverses modalités selon lesquelles les étudiants s’impliquent dans les réflexions et les décisions académiques relatives à l’organisation des études médicales et présenter les structures institutionnelles dédiées à cette action. Exégèse : Au niveau international, les étudiants en médecine sont regroupés dans la Fédération internationale des associations d’étudiants en médecine (International Federation of Medical Students’ Associations – IFMSA). Celle-ci entretient de multiples relations avec plusieurs organisations dans le domaine de l’enseignement médical, avec l’intention de représenter la voix des étudiants au niveau international (Association pour l’éducation médicale en Europe (Association for medical education in Europe – AMEE), Fédération mondiale pour l’enseignement de la médecine (World Federation of Medical Education – WFME). Au niveau national français, les étudiants en médecine sont représentés par l’ANEMF (Association nationale des étudiants en médecine de France), dont les activités sont présentées dans cet article

Real-time PCR quantification and spatio-temporal distribution of airborne inoculum of Puccinia triticina in Belgium

In order to better understand the epidemiology of Puccinia triticina and the relationship between airborne inoculum and disease severity, a method for quantifying airborne inoculum was developed using volumetric Burkard 7-day spore traps and real-time PCR. The method was applied using a spore trap network from 1 March to 30 June over a 5-year period. At one site, the inoculum was quantified continuously over 3 years, during which it showed a seasonal distribution, with the highest quantities and detection frequencies occurring between May and June. High mean daily quantities (65.8–121.2 spores/day) and detection frequencies (±20 % of days) were also reported after harvest from September to December. In the coldest months of the year, almost no detection was recorded (1–6 % of days). The study results indicate that the absence of inoculum in the air when upper leaves are emerging could be a limiting factor for the risk of epidemics. Mean daily quantities of airborne inoculum (0–131.4 spores/day) were measured from the beginning of stem elongation (GS30) to the flag leaf stage (GS39). These values were well correlated with the disease severity levels measured during grain development. A multiple regression analysis showed that total rainfall in late summer and autumn and mean minimum temperature in winter positively influence spore density between GS30 and GS39 in the following spring (R2 = 0.73). This relationship and the patterns of airborne inoculum observed in fields strongly suggest the existence of a ‘green bridge’ phenomenon in Belgium. Our study also showed that the quantification of airborne inoculum or its estimation using a weather-based predictive model could be useful for interpreting disease severity models and avoiding over-estimates of disease risk

Real-time PCR quantification and spatio-temporal distribution of airborne inoculum of Mycosphaerella graminicola in Belgium

Two kinds of propagules play a role in Mycosphaerella graminicola dissemination: splash-dispersed pycnidiospores and airborne sexual ascospores. A method based on real-time polymerase chain reaction (PCR) assay and using Burkard spore traps was developed to quantify M. graminicola airborne inoculum. The method was tested for its reliability and applied in a spore trap network over a 2-year period in order to investigate the spatio-temporal distribution of airborne inoculum in Belgium. At four experimental sites, airborne inoculum was detected in both years. A seasonal distribution was observed, with the highest mean daily quantities (up to 351.0 cDNA) trapped in July and with clusters detected from September to April. The first year of trapping, a mean daily quantity of 15.7 cDNA of M. graminicola airborne inoculum was also detected in the air above a building in a city where the spatio-temporal distribution showed a similar pattern to that in the field. Mean daily quantities of up to 60.7 cDNA of airborne inoculum were measured during the cereal stem elongation and flowering stages, suggesting that it contributes to the infection of upper leaves later in the season. Most detection, however, tended to occur between flowering and harvest, suggesting significant production of pseudothecia during that period. Variations in mean daily quantities from 1.0 to 48.2 cDNA were observed between sites and between years in the patterns of airborne inoculum. After stem elongation, the quantities detected at a site were positively correlated with the disease pressure in the field. Quantities trapped at beginning of the growing season were also well correlated with the disease level the previous year. Multiple regressions revealed that some factors partly explain the daily variations of airborne inoculum