From Central Asian Mountain Forests to European Fields: Genetic Structure of Wild and Cultivated Apricots is Linked to a Loss of Resistance to Plum Pox Potyvirus (sharka)

Apricot (Prunus armeniaca L.) is an important horticultural stone fruit species in the Northern hemisphere, where it is being severely threatened by Plum Pox Virus (PPV) infection (sharka disease). Domestication occurred thousands of years ago in Central Asia both in eastern (China) and western (Irano-Caucasian and European) areas. The apricot wild progenitor, P. armeniaca vulgaris, is still present as a forest tree in its native area, on the slopes of the Tien Shan range, where it co-occurs with the wild apple species, Malus sieversii. In this study, we investigated patterns of molecular diversity and genetic structure using microsatellite markers in a dataset of 380 wild apricot accessions collected in Central Asia, natural populations (Kazakhstan, Uzbekistan, Western China and Kyrgyzstan). They were compared with Western and Eastern cultivated relatives in order to determine putative geographic origin of European cultivated apricots and to reconstruct its evolutionary history. We observed high levels of genetic diversity in Central Asian and Chinese germplasm, in agreement with an origin of this species in this region. Three main genetic clusters were identified, corresponding to different human usages and geographic ranges: a) cultivars and landraces from European and Irano-caucasian countries, b) Chinese cultivars and landraces, and c) wild forms of P. armeniaca from Central Asia. A second level of genetic subdivision was identified within the wild accessions. Lastly, we unraveled the origin of resistance to PPV and present here preliminary results on its variability within the native apricot gene-pool.