Nematodes’ adaptation capacity undermines durability of potato’s pyramided resistance

A recent study made in the framework of NEM-EMERGE, led by partners from INRAE (France), has revealed that the adaptation ability of the nematode Globodera pallida compromises the durability of pyramidal resistance in potato plants. The findings have been published in the journal Evolutionary Applications.

The deployment of resistant plants, although initially efficient, has shown limited durability, due to the emergence of virulent pathogen populations that overcome resistance, particularly in the case of repeated use of monocultures of these resistant potato varieties. These observations underline the urgent need to develop resistance strategies that are not only effective but also sustainable.

Among the different strategies that can be used to increase the durability of plants’ genetic resistance, the NEM-EMERGE researchers focused on the so-called gene pyramiding, consisting of making a single plant contain more than one resistance gene. Theoretical studies and experimental works suggest that the pyramiding of resistance genes makes the plants more efficient and more difficult to overcome than plants with individual resistance genes, as it imposes stronger and more complex selective constraints on the nematode. However, if a virulent pathogen capable of overcoming all resistance genes emerges, the break is complete, leading to the loss of all resistance components at once. Researchers, therefore, considered it crucial to better understand the evolutionary pathways that could lead to such an adaptation.

In the piece of work carried out, the researchers compared the capacity of Globodera pallida nematodes to overcome different types of resistance conferred by different resistance genes, both individually and combined (with pyramidal resistance). They compared nematodes’ adaptation capacity in three types of potato plants: one containing a minor resistance gene, another containing a major resistance gene, and another containing both genes. They compared

Through experimental evolution experiments, they were able to measure nematodes’ virulence after ten generations reared on the abovementioned plants. They saw a gradient of resistance efficacy, being the lowest resistance conferred by the minor resistance gene and the highest resistance conferred by the plants with pyramidal resistance. However, after ten generations, even the resistance provided by the pyramidal resistance was compromised, particularly by nematodes that were already virulent to one of the two resistances. This fact highlights “the importance of taking evolutionary pathways into account in resistance deployment”, stress the authors.