Crop‐to‐wild gene flow and spatial genetic structure in the closest wild relatives of the cultivated apple

Abstract

Crop‐to‐wild gene flow have important evolutionary and ecological consequences and require careful consideration in conservation programs for wild genetic resources of potential use in breeding programs and in assessments of the risk of transgene escape into natural ecosystems. Using 26 microsatellites and a set of 1181 trees, we investigated the extent of introgression from the cultivated apple, Malus domestica, to its three closest wild relatives, M. sylvestris in Europe, M. orientalis in the Caucasus, and M. sieversii in Central Asia. We found footprints of introgression from M. domestica to M. orientalis (3.2% of hybrids), M. sieversii (14.8%), and M. sylvestris (36.7%). Malus sieversii and M. orientalis presented weak, but significant genetic structures across their geographic range. Malus orientalis displayed genetic differentiation with three differentiated populations in Turkey, Armenia, and Russia. Malus sieversii consisted of a main population spread over Central Asia and a smaller population in the Tian Shan Mountains. The low Sp values suggest high dispersal capacities for the wild apple relatives. High potential for crop‐to‐wild gene flow in apples needs to be considered in the implementation of in situ and ex situ actions for the conservation of wild apple genetic resources potentially useful to plant breeding.

Anthropogenic and natural drivers of gene flow in a temperate wild fruit tree: a basis for conservation and breeding programs in apples

“…The suitability for population genetic analysis of the markers used was demonstrated in previous studies (Cornille et al. , ,b).…”

“…Since its introduction into Europe by humans 1500 years ago, the cultivated apple has acted as a source of genes for introgression into the European wild apple (Cornille et al. ). We found that the rates of crop‐to‐wild introgression varied across Europe and could be accounted for by direct and indirect anthropogenic factors.…”

“…In addition to the 599 samples of M. sylvestris from Europe previously studied (Cornille et al. ,b) (38 sites), we collected a further denser sample of 1290 M. sylvestris trees (28 sites), mostly in France (20 sites, N = 1092), but also in Denmark (6 sites, N = 162), Italy (1 site, N = 5) and Belgium (1 site, N = 31). In total, 1889 M. sylvestris trees from 66 sites were analyzed for this study.…”

“…A lack of consideration of intraspecies genetic structure in STRUCTURE analyses can bias the interpretation of introgression rates (Kalinowski ; Cornille et al. ). We ran STRUCTURE, assuming K = 1 to K = 9 clusters, on the whole dataset including M. sylvestris ( N = 1889) and M. domestica ( N = 339).…”

“…; Cornille et al. ). Investigations of the demographic history of the European wild apple have revealed the existence of three main genetic groups shaped by past climate change during the Pleistocene (Cornille et al.…”