Insights Into the Almond Domestication History

Understanding crop domestication offers crucial insights into the evolutionary processes that drive population divergence and adaptation. It also informs the identification of genetically diverse wild germplasm, which is essential for breeding and conservation efforts. While domestication has been extensively studied in many Mediterranean fruit trees, the evolutionary history of the almond (Prunus dulcis) remains comparatively underexplored. To address this, we analyzed 209 wild and cultivated almond accessions sampled across Eurasia and genotyped with 23 microsatellite markers. Using population genetics and coalescent-based inference, we reconstructed the domestication history of P. dulcis and its relationships with wild relatives. Bayesian clustering revealed four genetically distinct clusters of cultivated almonds: Turkish, Caucasian-Central Asian, Southern Spanish, and European/North American. These groups were differentiated from wild almond species-including Prunus turcomanica, Prunus orientalis, Prunus fenzliana, and Prunus spinosissima-each forming its gene pool across the Middle East and Central Asia. Approximate Bayesian Computation (ABC) supported a single domestication event in the Middle East, originating from either P. orientalis or P. turcomanica, with subsequent gene flow from P. fenzliana and P. spinosissima into the Turkish and Central Asian cultivated gene pools, respectively. We also inferred reciprocal introgression from cultivated almonds back into wild populations. Notably, sharka resistance-caused by plum pox virus (PPV)-was identified in three P. dulcis clusters and P. fenzliana, suggesting that resistance may have arisen independently or been maintained through crop-wild introgression. Together, our results highlight a complex and protracted domestication history for almond, shaped by contributions from multiple wild relatives and recurrent gene flow. These findings enhance our understanding of perennial crop evolution and underscore the value of wild germplasm in breeding programs aimed at increasing resilience in fruit trees.