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

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, , to its three closest wild relatives, in Europe, in the Caucasus, and in Central Asia. We found footprints of introgression from to (3.2% of hybrids), (14.8%), and (36.7%). and presented weak, but significant genetic structures across their geographic range. displayed genetic differentiation with three differentiated populations in Turkey, Armenia, and Russia. consisted of a main population spread over Central Asia and a smaller population in the Tian Shan Mountains. The low 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 and actions for the conservation of wild apple genetic resources potentially useful to plant breeding.