Genome of tetraploid sour cherry (Prunus cerasus L.) ‘Montmorency’ identifies three distinct ancestral Prunus genomes

Sour cherry(Prunus cerasus L.)is a valuable fruit crop in the Rosaceae family and a hybrid between progenitors closely related to extant Prunus fruticosa(ground cherry)and Prunus avium(sweet cherry).Here we report a chromosome-scale genome assembly for sour cherry cultivar Montmorency,the predominant cultivar grown in the USA.We also generated a draft assembly of P.fruticosa to use alongside a published P.avium sequence for syntelog-based subgenome assignments for‘Montmorency’and provide compelling evidence P.fruticosa is also an allotetraploid.Using hierarchal k-mer clustering and phylogenomics,we show‘Montmorency’is trigenomic,containing two distinct subgenomes inherited from a P.fruticosa-like ancestor(A and A’)and two copies of the same subgenome inherited from a P.avium-like ancestor(BB).The genome composition of‘Montmorency’is AA’BB and little-to-no recombination has occurred between progenitor subgenomes(A/A’and B).In Prunus,two known classes of genes are important to breeding strategies:the self-incompatibility loci(S-alleles),which determine compatible crosses,successful fertilization,and fruit set,and the Dormancy Associated MADS-box genes(DAMs),which strongly affect dormancy transitions and flowering time.The S-alleles and DAMs in‘Montmorency’and P.fruticosa were manually annotated and support subgenome assignments.Lastly,the hybridization event‘Montmorency’is descended from was estimated to have occurred less than 1.61 million years ago,making sour cherry a relatively recent allotetraploid.The‘Montmorency’genome highlights the evolutionary complexity of the genus Prunus and will inform future breeding strategies for sour cherry,comparative genomics in the Rosaceae,and questions regarding neopolyploidy.