Abstract
In view of major economic problems caused by viruses, the development of genetically resistant crops is critical for breeders but remains limited by the evolution of resistance-breaking virus mutants. During the plant breeding process, the introgression of traits from Crop Wild Relatives results in a dramatic change of the genetic background that can alter the resistance efficiency or durability. Here, we conducted a meta-analysis on 19 Quantitative Trait Locus (QTL) studies of resistance to viruses in plants. Frequent epistatic effects between resistance genes indicate that a large part of the resistance phenotype, conferred by a given QTL, depends on the genetic background. We next reviewed the different resistance mechanisms in plants to survey at which stage the genetic background could impact resistance or durability. We propose that the genetic background may impair effector-triggered dominant resistances at several stages by tinkering the NB-LRR (Nucleotide Binding-Leucine-Rich Repeats) response pathway. In contrast, effects on recessive resistances by loss-of-susceptibility—such as eIF4E-based resistances—are more likely to rely on gene redundancy among the multigene family of host susceptibility factors. Finally, we show how the genetic background is likely to shape the evolution of resistance-breaking isolates and propose how to take this into account in order to breed plants with increased resistance durability to viruses.
Highlights
In a given organism, the expression and effect of genes rely on a multitude of interactions within the genome and with the environment
We gathered scattered studies that have carried out a close examination of genetic background effects on plant resistance genes or Quantitative Trait Locus (QTL)
This question is of high and generic interest because the effect of genetic background determines the transferability of resistance genes or QTL, from one species to another, and the predictability and efficiency of genetic progress during breeding for resistance
Summary
The expression and effect of genes rely on a multitude of interactions within the genome and with the environment. In the view of a plant breeder, who aims at producing elite crops by introducing multiple traits originating from Crop Wild Relatives (CWR) into crops [4,5], it is understandable that the whole breeding process will be linked with numerous introgressions into the crop genome, resulting in profound changes in the genetic background. Plants have evolved sophisticated resistance mechanisms to pathogens, including viruses that can be responsible for heavy crop losses. Very briefly, those mechanisms can be categorized as resistance associated with pathogen recognition, followed by defense induction and resistance by the loss-of-susceptibility affecting plant factors on which the pathogen relies for infection. We discuss how the plant genetic background can affect the efficiency and durability of genetic resistance to viruses and what the potential underlying molecular mechanisms are. We will pay attention to what has been characterized on the resistance durability to other pathogens, as this may hint at future research directions
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