Role of the Genetic Background in Resistance to Plant Viruses

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.

A complex eIF4E locus impacts the durability of va resistance to Potato virus Y in tobacco

“…Some potyviruses can also use several eIF4E isoforms in a given host (Gauffier et al , ; Jenner et al , ; Mazier et al , ; Xu et al , ). This suggests that in the absence of a functional eIF4E‐1 in va ‐resistant genotypes, RB PVY variants may use another eIF4E isoform, similar to the situation when TuMV overcomes an eIFiso4E loss‐of‐function in Arabidopsis through VPg mutations allowing recruitment of eIF4E1 (Bastet et al , ; Gallois et al , ). However, our data suggest that the situation is even more complex in tobacco, and that besides the potential use of an eIF(iso)4E copy by RB PVY, as suggested by Takakura et al (), at least two other eIF4E copies may play a role in va resistance durability.…”

“…It is not currently possible to order in a cause and effect model these elements but, with its multiple levels, the durability/ eIF4E‐2 correlation appears to be the most promising. It should be noted that homeostatic control feedback mechanisms between eIF4E family members to compensate loss of function has been demonstrated in plants (Gallois et al , ). This was previously reported in Arabidopsis, where eIF4E‐1 protein concentration increases to compensate for loss of eIFiso4E in the KO‐eIF(iso)4E (Duprat et al , ).…”

“…Even if the exact mechanism(s) involved in eIF4E ‐mediated resistance are still unclear (Wang and Krishnaswamy, ), it has been shown that the viral genome linked protein (VPg) can interact with eIF4E, mimicking the 5’ cap structure of messenger RNAs (mRNAs). In addition, potyviruses can evolve towards resistance breaking through the acquisition of mutations that either restore compatibility of their VPg with the host mutant eIF4E or allow an interaction with another member of the eIF4E family (Charron et al , ; Gallois et al , , ; Lebaron et al , ; Takakura et al , ).…”

A Major QTL Located in Chromosome 8 of Cucurbita moschata Is Responsible for Resistance to Tomato Leaf Curl New Delhi Virus

“…The role of the genetic background in resistance to plant viruses is considered determinant in breeding programs when transferring QTLs from one species to another. Gallois et al (2018) have studied and reviewed the effect of epistatic relationship with QTL analysis on virus resistance, suggesting that a major-effect QTL (proportion of phenotypic variance explained by the QTL R 2 > 0.60) could be more susceptible to genetic background influence than minor-effect QTLs. This statement supports the incomplete penetrance obtained when we tried to transfer the QTL conferring resistance to ToLCNDV from chromosome 8 of C. moschata into C. pepo background.…”

Appraisal of Genetics and Heterosis of Important Traits in Chilli Pepper Cultivated under the Influence of Chilli Leaf Curl Virus Disease

“…Screening of germplasm under natural epiphytotic and glasshouse conditions using viruliferous whiteflies is followed to identify the source of resistance against the ChiLCV [18]. However, a clear understanding of the underlying genetics of disease resistance and its inheritance pattern helps to select appropriate breeding strategies for successful introgression of the resistance genes [19][20][21].…”