Biology subjects

Fournet, S.

Publications and source records attributed to Fournet, S..

3 recordsLinked to original sources

bioRxiv2024

A diagnostic gap to fill: Development of molecular tools to distinguish the plant-parasitic nematode species Heterodera carotae and Heterodera cruciferae

The carrot-parasitic nematode, Heterodera carotae, is an important pest causing qualitative and quantitative production losses across several countries worldwide and must be carefully identified and monitored. Indeed, in culture crops, Heterodera carotae and Heterodera cruciferae, two genetically closely related species from the Goettingiana group, can be found in mixture and are virtually morphologically non-recognizable. However, only H. carotae is able to develop on carrot. To monitor carrot production and set up suitable H. carotae control plans, simple and reliable diagnostic methods to detect and identify these two species are needed. In this study, we developed and successfully tested two real-time PCR protocols (SYBR Green singleplex and TaqMan multiplex real-time PCRs) against both sister species: H. carotae and H. cruciferae. Using two specific sets of primers targeting the two species, which were designed from sequences containing microsatellite loci, we managed, whatever the methods, to distinguish the two species. Moreover, we showed a higher specificity using the TaqMan assays (test on cysts) but a better sensitivity (tests on J2 juvenile larvae) with the SYBR Green assays. In this study, we thus proposed two useful and reliable diagnostic tools to enable farmers and scientists to rapidly detect two plant-parasitic nematodes and supervise agricultural management.

molecular biology↗

bioRxiv2021

The quasi-universality of nestedness in the structure of quantitative plant-parasite interactions

AO_SCPLOWBSTRACTC_SCPLOWUnderstanding the relationships between host range and pathogenicity for parasites, and between the efficiency and scope of immunity for hosts are essential to implement efficient disease control strategies. In the case of plant parasites, most studies have focused on describing qualitative interactions and a variety of genetic and evolutionary models has been proposed in this context. Although plant quantitative resistance benefits from advantages in terms of durability, we presently lack models that account for quantitative interactions between plants and their parasites and the evolution of these interactions. Nestedness and modularity are important features to unravel the overall structure of host-parasite interaction matrices. Here, we analysed these two features on 32 matrices of quantitative pathogenicity trait data gathered from 15 plant-parasite pathosystems consisting of either annual or perennial plants along with fungi or oomycetes, bacteria, nematodes, insects and viruses. The performance of several nestedness and modularity algorithms was evaluated through a simulation approach, which helped interpretation of the results. We observed significant modularity in only six of the 32 matrices, with two or three modules detected. For three of these matrices, modules could be related to resistance quantitative trait loci present in the host. In contrast, we found high and significant nestedness in 30 of the 32 matrices. Nestedness was linked to other properties of plant-parasite interactions. First, pathogenicity trait values were explained in majority by a parasite strain effect and a plant accession effect, with no or minor parasite-plant interaction term. Second, correlations between the efficiency and scope of the resistance of plant genotypes, and between the host range breadth and pathogenicity level of parasite strains were overall positive. This latter result questions the efficiency of strategies based on the deployment of several genetically-differentiated cultivars of a given crop species in the case of quantitative plant immunity.

pathology↗

bioRxiv2017

Effective population size and durability of plant resistances in the potato cyst nematode Globodera pallida

O_LIThe effective size of a population is the size of an ideal population which would drift at the same rate as the real population. The balance between selection and genetic drift depends on the population size expressed as the genetically effective population size (Ne), rather than the real numbers of individuals in the population (N).\nC_LIO_LIThe objectives of the present study were to estimate Ne in the potato cyst nematode Globodera pallida using artificial populations and to explore the link between Ne and the durability of plant resistances.\nC_LIO_LIUsing a temporal method on 24 independent pairs of initial and final populations, the median Ne was 58 individuals.\nC_LIO_LINe is commonly lower than N but in our case the Ne/N ratio was extremely low because G. pallida populations deviate in structure from the assumptions of the ideal population by having unequal sex-ratios, high levels of inbreeding and a high variance in family sizes. The consequences of a low Ne could be important for the control of phytoparasitic nematodes because G. pallida populations will have a low capacity to adapt to changing environments unless selection intensity is very strong, which could be greatly beneficial for long-term use of plant resistances.\nC_LI

evolutionary biology↗