Genome of the North American wild apple species Malus angustifolia

Apple (Malus x domestica Borkh.) production faces many challenges stemming from abiotic and biotic stresses. Abiotic stressors, such as extreme temperatures, droughts, and spring frosts, can lead to diminished yields and tree loss, while biotic stresses like fire blight and pest infestations further reduce tree health and fruit quality. To lessen the threat of these challenges, plant breeders aim to introduce resistance and resilience genes into cultivated varieties. However, high-relatedness among cultivated varieties and breeding lines, coupled with the long juvenility and generation times in apples, hinder the breeding process. The introduction of resistance traits from wild relatives is also constrained by these factors, as well as the lack of genomic resources that could assist in accelerating the introgression process. Herein, we report the assembly and annotation of Malus angustifolia, the Southern Crabapple, one of Eastern North Americas native species. Using a combination of Pacific Biosciences High Fidelity reads, Next-generation short read sequencing, as well as chromatin conformation capture sequencing, we achieve an extremely contiguous haplotype-resolved assembly. We perform comparative haplotypic analyses to identify SNPs and large structural variants, shedding light on the genomic landscape of M. angustifolia. Finally, we explore the phylogenetic and syntenic relationships between Eurasian Malus progenitors and the recently sequenced North American species, contributing valuable insights to the broader understanding of apple evolution and potential breeding strategies.