Prunus genetics and applications after de novo genome sequencing:achievements and prospects

Prior to the availability of whole-genome sequences,our understanding of the structural and functional aspects of Prunus tree genomes was limited mostly to molecular genetic mapping of important traits and development of EST resources.With public release of the peach genome and others that followed,significant advances in our knowledge of Prunus genomes and the genetic underpinnings of important traits ensued.In this review,we highlight key achievements in Prunus genetics and breeding driven by the availability of these whole-genome sequences.Within the structural and evolutionary contexts,we summarize:(1)the current status of Prunus whole-genome sequences;(2)preliminary and ongoing work on the sequence structure and diversity of the genomes;(3)the analyses of Prunus genome evolution driven by natural and man-made selection;and(4)provide insight into haploblocking genomes as a means to define genome-scale patterns of evolution that can be leveraged for trait selection in pedigree-based Prunus tree breeding programs worldwide.Functionally,we summarize recent and ongoing work that leverages whole-genome sequences to identify and characterize genes controlling 22 agronomically important Prunus traits.These include phenology,fruit quality,allergens,disease resistance,tree architecture,and self-incompatibility.Translationally,we explore the application of sequence-based marker-assisted breeding technologies and other sequence-guided biotechnological approaches for Prunus crop improvement.Finally,we present the current status of publically available Prunus genomics and genetics data housed mainly in the Genome Database for Rosaceae(GDR)and its updated functionalities for future bioinformatics-based Prunus genetics and genomics inquiry.

Apple whole genome sequences:recent advances and new prospects

In 2010,a major scientific milestone was achieved for tree fruit crops:publication of the first draft whole genome sequence(WGS)for apple(Malus domestica).This WGS,v1.0,was valuable as the initial reference for sequence information,fine mapping,gene discovery,variant discovery,and tool development.A new,high quality apple WGS,GDDH13 v1.1,was released in 2017 and now serves as the reference genome for apple.Over the past decade,these apple WGSs have had an enormous impact on our understanding of apple biological functioning,trait physiology and inheritance,leading to practical applications for improving this highly valued crop.Causal gene identities for phenotypes of fundamental and practical interest can today be discovered much more rapidly.Genome-wide polymorphisms at high genetic resolution are screened efficiently over hundreds to thousands of individuals with new insights into genetic relationships and pedigrees.High-density genetic maps are constructed efficiently and quantitative trait loci for valuable traits are readily associated with positional candidate genes and/or converted into diagnostic tests for breeders.We understand the species,geographical,and genomic origins of domesticated apple more precisely,as well as its relationship to wild relatives.The WGS has turbo-charged application of these classical research steps to crop improvement and drives innovative methods to achieve more durable,environmentally sound,productive,and consumer-desirable apple production.This review includes examples of basic and practical breakthroughs and challenges in using the apple WGSs.Recommendations for“what’s next”focus on necessary upgrades to the genome sequence data pool,as well as for use of the data,to reach new frontiers in genomics-based scientific understanding of apple.

RosBREED:bridging the chasm between discovery and application to enable DNA-informed breeding in rosaceous crops

The Rosaceae crop family(including almond,apple,apricot,blackberry,peach,pear,plum,raspberry,rose,strawberry,sweet cherry,and sour cherry)provides vital contributions to human well-being and is economically significant across the U.S.In 2003,industry stakeholder initiatives prioritized the utilization of genomics,genetics,and breeding to develop new cultivars exhibiting both disease resistance and superior horticultural quality.However,rosaceous crop breeders lacked certain knowledge and tools to fully implement DNA-informed breeding—a“chasm”existed between existing genomics and genetic information and the application of this knowledge in breeding.The RosBREED project(“Ros”signifying a Rosaceae genomics,genetics,and breeding community initiative,and“BREED”,indicating the core focus on breeding programs),addressed this challenge through a comprehensive and coordinated 10-year effort funded by the USDA-NIFA Specialty Crop Research Initiative.RosBREED was designed to enable the routine application of modern genomics and genetics technologies in U.S.rosaceous crop breeding programs,thereby enhancing their efficiency and effectiveness in delivering cultivars with producer-required disease resistances and market-essential horticultural quality.This review presents a synopsis of the approach,deliverables,and impacts of RosBREED,highlighting synergistic global collaborations and future needs.Enabling technologies and tools developed are described,including genome-wide scanning platforms and DNA diagnostic tests.Examples of DNA-informed breeding use by project participants are presented for all breeding stages,including pre-breeding for disease resistance,parental and seedling selection,and elite selection advancement.The chasm is now bridged,accelerating rosaceous crop genetic improvement.

A roadmap for research in octoploid strawberry

The cultivated strawberry(Fragaria×ananassa)is an allo-octoploid species,originating nearly 300 years ago from wild progenitors from the Americas.Since that time the strawberry has become the most widely cultivated fruit crop in the world,universally appealing due to its sensory qualities and health benefits.The recent publication of the first highquality chromosome-scale octoploid strawberry genome(cv.Camarosa)is enabling rapid advances in genetics,stimulating scientific debate and provoking new research questions.In this forward-looking review we propose avenues of research toward new biological insights and applications to agriculture.Among these are the origins of the genome,characterization of genetic variants,and big data approaches to breeding.Key areas of research in molecular biology will include the control of flowering,fruit development,fruit quality,and plant–pathogen interactions.In order to realize this potential as a global community,investments in genome resources must be continually augmented.