Durability of plant major resistance genes to pathogens depends on the genetic background, experimental evidence and consequences for breeding strategies

Abstract

Summary The breakdown of plant resistance by pathogen populations is a limit to the genetic control of crop disease. Polygenic resistance is postulated as a durable alternative to defeated major resistance genes. Here, we tested this postulate in the pepper–Potato virus Y interaction. The virus was selected for virulence towards monogenic and polygenic host resistance, using serial inoculations in laboratory and in natural epidemic conditions. The frequency of resistance breakdown and the genetic changes in the virus avirulence gene were analysed. The monogenic resistance provided by the pvr23 gene was defeated at high frequency when introgressed in a susceptible genetic background whereas it was not when combined to partial resistance quantitative trait loci. The suppression of emergence of virulent mutants because of the genetic background resulted both from a differential selection effect and the necessity for the virus to generate multiple mutations. The virus adaptation to the polygenic resistance required a step‐by‐step selection with a primary selection for virulence towards the major gene, followed by selection for adaptation to the genetic background. Polygenic resistance proved more durable than monogenic resistance, but breeding strategies giving priority to major resistance factors may jeopardize the progress in durability expected from polygenic resistance.

Identification and mapping of quantitative resistance to late blight (Phytophthora infestans) in Solanum habrochaites LA1777

“…Quantitative resistance in plants has been shown to be more durable (Brun et al 2010;Palloix et al 2009). In S. habrochaites a high level of quantitative resistance to several isolates has been found ).…”

“…Not all QTLs were identified in each experiment and in all lines with overlapping introgressions, indicating that most QTLs have a limited effect and interactions between QTLs as well as between QTLs and environment play a role in obtaining a high level of resistance. Combining QTLs and single resistance genes can be beneficial for durability of the resistance to several fungi (Brun et al 2010;Palloix et al 2009;Stall et al 2009). Therefore we suggest to develop combinations of several QTLs or QTLs and single genes, not only from one wild species but also from different wild species.…”

“…Quantitative resistance is often non racespecific and more durable than qualitative resistance governed by R-genes (Brun et al 2010;Palloix et al 2009;Robert et al 2009). For resistance to late blight, research in potato has been since 1970 focusing on introducing quantitative resistance (Wastie 1991), in spite of the fact that already eleven single R-genes were known.…”

Evolution and Emergence of Plant Viruses

“…These studies are based in the analysis a posteriori of epidemiological data. The scarce experimental studies about overcoming resistances determined by major genes, dominant or recessive (Palloix et al, 2009), are affected by the difficulty of extrapolating laboratory fitness data to field conditions, since as we mentioned above, fitness depends on the conditions where it is evaluated.…”

Genetic mapping of three quantitative trait loci for soybean aphid resistance in PI 567324

“…The presence of such soybean aphid biotypes can decrease the effectiveness and sustainability of host-plant resistance provided by most single genes (R-genes). Therefore, it is necessary to find new aphid resistance sources with multigenic resistance, which can provide more durable resistance than single genes (Palloix et al, 2009).…”