Blueberry and cranberry pangenomes as a resource for future genetic studies and breeding efforts

Domestication of cranberry and blueberry began in the United States in the early 1800s and 1900s,respectively,and in part owing to their f lavors and health-promoting benefits are now cultivated and consumed worldwide.The industry continues to face a wide variety of production challenges(e.g.disease pressures),as well as a demand for higher-yielding cultivars with improved fruit quality characteristics.Unfortunately,molecular tools to help guide breeding efforts for these species have been relatively limited compared with those for other high-value crops.Here,we describe the construction and analysis of the first pangenome for both blueberry and cranberry.Our analysis of these pangenomes revealed both crops exhibit great genetic diversity,including the presence-absence variation of 48.4%genes in highbush blueberry and 47.0%genes in cranberry.Auxiliary genes,those not shared by all cultivars,are significantly enriched with molecular functions associated with disease resistance and the biosynthesis of specialized metabolites,including compounds previously associated with improving fruit quality traits.The discovery of thousands of genes,not present in the previous reference genomes for blueberry and cranberry,will serve as the basis of future research and as potential targets for future breeding efforts.The pangenome,as a multiple-sequence alignment,as well as individual annotated genomes,are publicly available for analysis on the Genome Database for Vaccinium-a curated and integrated web-based relational database.Lastly,the core-gene predictions from the pangenomes will serve useful to develop a community genotyping platform to guide future molecular breeding efforts across the family.

Genome mapping of postzygotic hybrid necrosis in an interspecific pear population

Deleterious epistatic interactions in plant inter-and intraspecific hybrids can cause a phenomenon known as hybrid necrosis,characterized by a typical seedling phenotype whose main distinguishing features are dwarfism,tissue necrosis and in some cases lethality.Identification of the chromosome regions associated with this type of incompatibility is important not only to increase our understanding of the evolutionary diversification that led to speciation but also for breeding purposes.Development of molecular markers linked to the lethal genes will allow breeders to avoid incompatible inbred combinations that could affect the expression of important agronomic tratis co-segregating with these genes.Although hybrid necrosis has been reported in several plant taxa,including Rosaceae species,this phenomenon has not been described previously in pear.In the interspecific pear population resulting from a cross between PEAR3(Pyrus bretschneideri×Pyrus communis)and‘Moonglow’(P.communis),we observed two types of hybrid necrosis,expressed at different stages of plant development.Using a combination of previously mapped and newly developed genetic markers,we identified three chromosome regions associated with these two types of lethality,which were genetically independent.One type resulted from a negative epistatic interaction between a locus on linkage group 5(LG5)of PEAR3 and a locus on LG1 of‘Moonglow’,while the second type was due to a gene that maps to LG2 of PEAR3 and which either acts alone or more probably interacts with another gene of unknown location inherited from‘Moonglow’.