Biology subjects

Gelisse, S.

Publications and source records attributed to Gelisse, S..

3 recordsLinked to original sources

bioRxiv2018

Sexual reproduction in the fungal foliar pathogen Zymoseptoria tritici is driven by antagonistic density-dependence mechanisms

This study provides empirical evidence for antagonistic density-dependence mechanisms driving sexual reproduction in the wheat fungal pathogen Zymoseptoria tritici. Biparental crosses with 12 increasing inoculum concentrations, in controlled conditions, showed that sexual reproduction in Z. tritici was impacted by an Allee effect due to mate limitation and a competition with asexual multiplication for resource allocation. We found that asexual multiplication was itself affected by competition for host resources between the two parental isolates, as illustrated by the decrease in asexual fruiting body density and sporulation intensity observed with increasing lesion density. Consistent with these results for controlled co-inoculation, we found that the intensity of sexual reproduction varied with both cropping period and the vertical position of the host tissues in the field. An optimal lesion density maximizing offspring (ascospores) number was established, and its eco-evolutionary consequences are considered here. Two ecological mechanisms may be involved: competition for resources between the two modes of reproduction (decrease in the host resources available for sexual reproduction due to their prior use in asexual multiplication), and competitive disequilibrium between the two parental isolates, due to differential interaction dynamics with the host, for example, leading to an imbalance between mating types. Conceptual models based on these results suggest that sexual reproduction plays a key role in the evolution of pathogenicity traits, including virulence and aggressiveness. Ecological knowledge about the determinants of sexual reproduction in Z. tritici may, therefore, open up new perspectives for the management of other fungal foliar pathogens with dual modes of reproduction.

microbiology↗

bioRxiv2018

Optimized real-time qPCR assays for detecting and quantifying the Fusarium and Microdochium species responsible for wheat head blight, as defined by MIQE guidelines

In order to better understand the Fusarium head blight disease, reliable real-time PCR assays for detection and quantification of fungal species belonging to the Fusarium and Microdochium genus are needed. Specific qPCR assays were developed for nine of those species. All criteria required for reproducing the assays are presented. The assays were species specific and allow quantification of at least 5 pg of fungal DNA and detection of 0.5 pg of fungal DNA per PCR reaction. Moreover we showed that the quantification performances of the tests were not altered in the presence of DNA of closely related species in the sample. The assays were tested on field samples and have been already used in greenhouse experiments.

molecular biology↗

bioRxiv2017

Trade-off between intra- and interannual scales in the evolution of aggressiveness in a local plant pathogen population

This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100039). The efficiency of plant resistance to fungal pathogen populations is expected to decrease over time, due to its evolution with an increase in the frequency of virulent or highly aggressive strains. This dynamics may differ depending on the scale investigated (annual or pluriannual), particularly for annual crop pathogens with both sexual and asexual reproduction cycles. We assessed this time-scale effect, by comparing aggressiveness changes in a local Zymoseptoria tritici population over an eight-month cropping season and a six-year period of wheat monoculture. We collected two pairs of subpopulations to represent the annual and pluriannual scales: from leaf lesions at the beginning and end of a single annual epidemic, and from crop debris at the beginning and end of a six-year period. We assessed two aggressiveness traits - latent period and lesion size - on sympatric and allopatric host varieties. A trend toward decreased latent period concomitant with a significant loss of variability was established during the course of the annual epidemic, but not over the six-year period. Furthermore, a significant cultivar effect (sympatric vs. allopatric) on the average aggressiveness of the isolates revealed host adaptation, arguing that the observed patterns could result from selection. We thus provide an experimental body of evidence of an epidemiological trade-off between the intra- and inter-annual scales in the evolution of aggressiveness in a local plant pathogen population. More aggressive isolates were collected from upper leaves, on which disease severity is usually lower than on the lower part of the plants left in the field as crop debris after harvest. We suggest that these isolates play little role in sexual reproduction, due to an Allee effect (difficulty finding mates at low pathogen densities), particularly as the upper parts of the plant are removed from the field, explaining the lack of transmission of increases in aggressiveness between epidemics.

epidemiology↗