Diversité des ressources génétiques chez le piment (Capsicum sp.) au sein de la collection INRA

* INRA, Centre d'Avignon, Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9 Diffusion du document : INRA, Centre d'Avignon, Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9National audienc

Impact of selection, genetic drift and viral accumulation on the evolution of a plant RNA virus

Genetic control is an efficient way to fight against crop disease, but this method is limited by the pathogen ability to evolve and break the resistance down. In the pepper-Potato virus Y (PVY) pathosystem, studies have demonstrated that the plant genetic background can increase the durability of the major resistance gene (Palloix et al., 2009), especially by constraining pathogen evolution (Quenouille et al., 2013). We conducted an experimental evolution to (i) measure the pathogen ability to adapt to plants combining major resistance gene and partially resistant genetic background and (ii) identify the role of the evolutionary forces induced by the genetic background on virus evolution

Vers une lutte durable contre les virus de plantes

National audienc

Transfer by marker-assisted backcross of QTLs confering resistance to Phytophthora capsici Leon originating from different accessions

* INRA Centre d'Avignon, Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9 Diffusion du document : INRA Centre d'Avignon, Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9National audienc

Quantitative trait loci in pepper control the effective population size of two RNA viruses at inoculation

International audienceInfection of plants by viruses is a complex process involving several steps: inoculation into plant cells, replication in inoculated cells and plant colonization. The success of the different steps depends, in part, on the viral effective population size (Ne), defined as the number of individuals passing their genes to the next generation. During infection, the virus population will undergo bottlenecks, leading to drastic reductions in Ne and, potentially, to the loss of the fittest variants. Therefore, it is crucial to better understand how plants affect Ne. We aimed to (i) identify the plant genetic factors controlling Ne during inoculation, (ii) understand the mechanisms used by the plant to control Ne and (iii) compare these genetic factors with the genes controlling plant resistance to viruses. Ne was measured in a doubled-haploid population of Capsicum annuum. Plants were inoculated with either a Potato virus Y (PVY) construct expressing the green fluorescent protein or a necrotic variant of Cucumber mosaic virus (CMV). Newas assessed by counting the number of primary infection foci on cotyledons for PVY or the number of necrotic local lesions on leaves for CMV. The number of foci and lesions was correlated (r=0.57) and showed a high heritability (h2=0.93 for PVY and h2=0.98 for CMV). The Ne of the two viruses was controlled by both common quantitative trait loci (QTLs) and virus-specific QTLs, indicating the contribution of general and specific mechanisms. The PVY-specific QTL colocalizes with a QTL that reduces PVY accumulation and the capacity to break down a major-effect resistance gene

The durability of a major resistance gene is affected by quantitative trait loci which also confer quantitative resistance to virus

Communication oraleNational audienc

Quantitative trait loci in pepper genome control the effective population size of two RNA viruses at inoculation

International audienceInfection of plants by viruses is a complex process that involves several steps: inoculation into plant cells, replication in inoculated cells, cell-to-cell movement during leaf colonization and long-distance movement during systemic infection. The success of the different steps is conditioned by the effective viral population size (Ne) defined as the number of individuals that pass their genes to the next generation. During the infection cycle, the virus population will endure several bottlenecks leading to drastic reductions in Ne and to the random loss of sorne virus variants. If strong enough, these bottlenecks could act against selection by eliminating the fittest variants. Therefore, a better understanding of how plant affects Ne rnay contribute to the developrnent of durable virus-resistant cultivars. We aimed to (i) identify plant genetic factors that control Ne at the inoculation step, (ii) understand the mechanisms used by the plant to control Ne and (iii) compare these genetic factors with other genes controlling virus life cycle and plant resistance durability. The virus effective population size was measured in a segregating population of 152 doubled-haploid lines of Capsicum annuum. Plants were inoculated mechanically either with a Patata virus Y (PVY) construct expressing the green fluorescent protein (OFP), or a necrotic variant of Cucumber mosaic virus (CMV), the CMV-N strain of Fulton. Ne was assessed by counting the number ofprimary infection foci observed on inoculated cotyledons under UV light for PVY -OFP or the number of necrotic local lesionsobserved on inoculated leaves for CMY-N. The numbers of primary infection foci and locallesions were correlated arnong the doubled-haploid lines (r=0.57) and showed a high heritability (h2=0.93 and 0.98 for PVY and CMV, respectively). The effective population size of the two viruses was shown to be controlled by botb common quantitative trait loci (QTLs) and virus-specifie QTLs, indicating the contribution ofboth general and specifie mechanisms. The PVY-specific QTL colocalizes with a QTL that had previously been shown to be involved in PVY accumulation and capacity to break amajor-effect resistance gene down

Genome-wide association mapping of loci implied in Potato virus Y resistance and tolerance in the pepper germplasm

National audienc

Genome-wide association mapping of QTLs implied in potato virus Y population sizes in pepper: evidence for widespread resistance QTL pyramiding.

International audienceIn this study, we looked for genetic factors in the pepper (Capsicum annuum) germplasm that control the number of potato virus Y (PVY) particles entering the plant (i.e. effective population size at inoculation) and the PVY accumulation at the systemic level (i.e. census population size). Using genotyping-by-sequencing (GBS) in a core collection of 256 pepper accessions, we obtained 10 307 single nucleotide polymorphisms (SNPs) covering the whole genome. Genome-wide association studies (GWAS) detected seven SNPs significantly associated with the virus population size at inoculation and/or systemic level on chromosomes 4, 6, 9 and 12. Two SNPs on chromosome 4 associated with both PVY population sizes map closely to the major resistance gene pvr2 encoding the eukaryotic initiation factor 4E. No obvious candidates for resistance were identified in the confidence intervals for the other chromosomes. SNPs detected on chromosomes 6 and 12 colocalized with resistance quantitative trait loci (QTLs) previously identified with a biparental population. These results show the efficiency of GBS and GWAS in C. annuum, indicate highly consistent results between GWAS and classical QTL mapping, and suggest that resistance QTLs identified with a biparental population are representative of a much larger collection of pepper accessions. Moreover, the resistance alleles at these different loci were more frequently combined than expected by chance in the core collection, indicating widespread pyramiding of resistance QTLs and widespread combination of resistance QTLs and major effect genes. Such pyramiding may increase resistance efficiency and/or durability

Constructing multiresistant genotypes of sweet pepper for cultivation in the tropics

* INRA Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9 Diffusion du document : INRA Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9International audienc