Research topics

IRHS
IRHS
Apple and pear resistance to diseases and pests
Research topics

Research topics

Stimulating plant defenses in commercial orchards or breeding new resistant apple and pear varieties are operational disease and pest control methods for which we develop upstream research programs. We especially focus on the genetic and molecular determinants of apple and pear resistance to scab (Venturia inaequalis and Venturia pirina), fire blight (Erwinia amylovora), rosy apple aphid (Dysaphis plantaginea) and psylla (Cacopsylla pyri). Integrated defense responses, from perception to induced defenses as well as constitutive defenses are investigated. Durability of resistance factors against V. inaequalis is explored in collaboration with the team EcoFun, taking into account the pathogen variability and its potential evolution. In collaboration with the team QualiPom, genetic diversity of disease resistance and other major traits are explored in germplasm collection, together with the implementation of marker-assisted selection and genomic selection.

Four main interconnected projects are conducted in a continuum of upstream/applied researches:

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Targeted genome engineering has recently emerged as an alternative to classical transgenic methods to achieve functional studies of genes, and to improve crop plants. Among other methods (zinc finger nucleases or TAL effector nucleases) the CRISPR-Cas methods proved to be the most effective, convenient and least expensive ones. To increase its ability to study gene function, but also to be able to provide expertise on any new varieties created using these tools, the ResPom team has decided a few years ago to develop such methods on apple and pear (figure presentation edition).
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In France, apple and pear old cultivars are conserved by numerous actors and represent a diversity reservoir that must be characterized from both phenotypic and genotypic point of view in order to better manage it and exploit its potential, specifically in a climate change context. We have been contributing for many years to the characterization of these genetic resources using microsatellite markers (SSR), and more recently SNPs, in collaboration with the VaDiPom team in charge of apple and pear genetic resources management.
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The accurate characterization of the genetic architecture of apple and pear resistance to their main pests is useful both to identify the combinations of major genes and QTLs necessary to build durable resistance and to progress in the understanding of the underlying mechanisms.
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Genomic prediction relies on the use of statistical models enabling to identify interesting individuals stemming from crosses at their youngest age, using only genotypic data. The models are built using genotypic and phenotypic data obtained on a so called training or reference population. Our team, together with the VaDiPom team and the Experimental Horticultural unit of INRAE in Angers (UE Horti), is part of a European consortium that created such a reference population for apple and planted it in a multisite orchard trial consisting of six locations, in Belgium, Spain, France, Italy, Poland, and Switzerland, in order to generate the required data for this approach. This represents a unique network to date for apple.
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The knowledge of pedigree relationships between cultivars enables both to bring information about breeding history over the past centuries and to estimate heritabilities and genetic correlations of economically interesting traits in modern breeding programs.
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Plant resistance inducers (PRIs) are defined as any substance, any extract of various organisms, or any non-pathogenic living microorganism able of promoting a state of resistance in a plant facing biotic stresses (definition of the Elicitra RMT; https://elicitra.org/). Activities of Respom team are characterized by a translational research, from the screening of such products on apple plantlets to the optimization of their efficiency in the orchard. The main research questions are i) do products claiming PRI activity really induce apple defenses? ii) which diseases or pests can they control? iii) what are the molecular mechanisms underlying resistance? iv) what are the factors influencing their efficacy? and v) how can they be integrated into pest management programs?
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Plant defense responses are made of a succession of molecular events starting fromwith the detection of the invader, followed by the activation of signaling cascades (first at the cellular level, then throughout the entire organism), and finally leading to the production of a molecular cocktail harming the pest . A part of our research activity is focused on the identification of the different ingredients of this cocktail, and on the understanding of their mode of action. The question raised by these studies is: how do these apple immune end-players (effectors) finally work to modify the course of the plant/pest interaction in a way that is beneficial for the plant?

Modification date : 20 December 2023 | Publication date : 21 July 2011 | Redactor : CD