Impacts of Resistance Gene Genetics, Function, and Evolution on a Durable Future

Abstract

Studies on resistance gene function and evolution lie at the confluence of structural and molecular biology, genetics, and plant breeding. However, knowledge from these disparate fields has yet to be extensively integrated. This review draws on ideas and information from these different fields to elucidate the influences driving the evolution of different types of resistance genes in plants and the concurrent evolution of virulence in pathogens. It provides an overview of the factors shaping the evolution of recognition, signaling, and response genes in the context of emerging functional information along with a consideration of the new opportunities for durable resistance enabled by high-throughput DNA sequencing technologies.

Rationalization of genes for resistance to Bremia lactucae in lettuce

“…The plethora of known resistance genes and those now in multiple public and commercial breeding pipelines provides the opportunity for rational deployment of resistance genes (Dm and QTLs; Michelmore et al 2013b). Pyramids of resistance genes based the nomenclature proposed here that are effective against the diversity of B. lactucae should be generated so as to maximize the evolutionary hurdle required for B. lactucae to become virulent.…”

Tomato I2 Immune Receptor Can Be Engineered to Confer Partial Resistance to the Oomycete Phytophthora infestans in Addition to the Fungus Fusarium oxysporum

“…Plants have evolved various disease resistance mechanisms to defend against pathogens. Sustainable crop improvement based on these mechanisms often involve R genes -plant loci that encode immune receptors (Cook 2000, Michelmore, Christopoulou et al 2013. One challenge is to engineer plants with broad-spectrum disease resistance, i.e.…”

An evolutionary ecology perspective to address forest pathology challenges of today and tomorrow

“…These failures have pushed breeders to consider other types of resistance, such as polygenic partial resistance, with the goal to slow down the evolution of virulent pathogen variants, thus increase the durability of resistance (Dowkiw et al 2012). The increasing knowledge of plant-pathogen molecular interactions and technological advances are enabling the discovery and functional profiling of new resistance genes, the breakdown of which would incur high fitness costs in corresponding virulent pathogens (Vleeshouwers et al 2008;Michelmore et al 2013). Tolerance in its restricted meaning (i.e., mechanisms that reduce the host fitness costs of infection, Roy and Kirchner 2000;Simms 2000) has been the subject of a growing interest as a potentially more stable defense component than true resistance since it was considered to place little or no selective pressure on the pathogen (Schafer 1971;Ney et al 2013;Ennos 2015).…”

“…Indeed, durable resistance to pathogens is a population attribute that can only be assigned retrospectively (Johnson 1984). Rather than relying on "durable resistance genes," durable resistance should be considered in terms of a strategy to minimise the pace of evolution of virulence in the pathogen population (REX Consortium 2013; Michelmore et al 2013). This can be achieved by a variety of approaches based on an adequate deployment of multiple resistance genes either by pyramiding and/or by heterogeneous deployment in space and time, so as to diversify the selection pressure on the pathogen (McDonald and Linde 2002;Michelmore et al 2013;REX Consortium 2013).…”

“…Rather than relying on "durable resistance genes," durable resistance should be considered in terms of a strategy to minimise the pace of evolution of virulence in the pathogen population (REX Consortium 2013; Michelmore et al 2013). This can be achieved by a variety of approaches based on an adequate deployment of multiple resistance genes either by pyramiding and/or by heterogeneous deployment in space and time, so as to diversify the selection pressure on the pathogen (McDonald and Linde 2002;Michelmore et al 2013;REX Consortium 2013). Growing clonal mixtures of 5-20 genotypes for short-rotation coppice of willow has proven to be feasible and effective for both disease reduction and yield increase over a long term (McCracken et al 2011).…”