Genetic structure of Malus sylvestris and potential link with preference/performance by the rosy apple aphid pest Dysaphis plantaginea

Thomas Denoirjean,Xilong Chen,Géraldine Doury,Arnaud Ameline,Thierry Hance,Amandine Cornille

doi:10.1038/s41598-021-85014-x

Abstract

The European crabapple Malus sylvestris, a crop wild relative of Malus domestica, is a major contributor to the cultivated apple genome and represents a potential source of interesting alleles or genes, particularly pest resistance traits. An original approach was used to explore the trophic interaction between M. sylvestris populations and its pest, the rosy apple aphid (Dysaphis plantaginea). Using 13 microsatellite markers, population genetic structure and level of crop-to-wild introgressions were inferred between M. sylvestris seedlings from three sites in Europe (Denmark, France, Romania), and M. domestica seedlings. Genetically characterized plants were also used to analyze aphid feeding behavior and fitness parameters. First, aphids submitted to two genetically close M. sylvestris populations (the Danish and French) exhibited similar behavioral parameters, suggesting similar patterns of resistance in these host plants. Second, the Romanian M. sylvestris population was most closely genetically related to M. domestica. Although the two plant genetic backgrounds were significantly differentiated, they showed comparable levels of sensitivity to D. plantaginea infestation. Third, aphid fitness parameters were not significantly impacted by the host plant’s genetic background. Finally, crop-to-wild introgression seemed to significantly drive resistance to D. plantaginea independent of host plant population genetic structure, with hybrids being less suitable hosts.

Highlights

Intense farming practices can lead to harmful impacts on the environment and human health
The cultivated apple continued its journey along the Silk Routes where it hybridized with local wild apple tree species: first to a little extent with Malus orientalis Uglitz. in the Caucasus, and later on (~ 1500 YA), massively in Europe with Malus sylvestris (L.) Mill.[4]
STRUCTURE analyses revealed a clear split between M. domestica and M. sylvestris seedlings for K = 3 (Supplementary Fig. S1)

Summary

Introduction

Intense farming practices can lead to harmful impacts on the environment and human health. In the context of breeding programs relying on CWR genetic traits, the cultivated apple tree Malus domestica Borkh appears to be an ideal model system for reducing the environmental impacts of food production. To reduce reliance on pesticide applications, apple breeding programs should test potential sources of resistance alleles such as the three potential local wild apple species in Eurasia. Population genetics analyses revealed that the cultivated M. domestica originated from the wild apple Malus sieversii Ledeb. Previous population genetic analyses of M sylvestris populations using microsatellite markers revealed five genetic clusters spread throughout Scandinavia, Western Europe (mostly in France), Eastern Europe, Central Europe, and Italy[6,7] These five populations may possess adaptive alleles associated with specific environmental conditions or local parasites. Responses to pathogens and pests among these wild apple genetic groups have yet to be explored

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Conclusion