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.

High-density linkage map construction and identification of loci regulating fruit quality traits in blueberry

Fruit quality traits play a significant role in consumer preferences and consumption in blueberry(Vaccinium corymbosum L).The objectives of this study were to construct a high-density linkage map and to identify the underlying genetic basis of fruit quality traits in blueberry.A total of 287 F_(1) individuals derived from a cross between two southern highbush blueberry cultivars,‘Reveille’and‘Arlen’,were phenotyped over three years(2016–2018)for fruit quality-related traits,including titratable acidity,pH,total soluble solids,and fruit weight.A high-density linkage map was constructed using 17k single nucleotide polymorphisms markers.The linkage map spanned a total of 1397 cM with an average inter-loci distance of 0.08 cM.The quantitative trait loci interval mapping based on the hidden Markov model identified 18 loci for fruit quality traits,including seven loci for fruit weight,three loci for titratable acidity,five loci for pH,and three loci for total soluble solids.Ten of these loci were detected in more than one year.These loci explained phenotypic variance ranging from 7 to 28% for titratable acidity and total soluble solid,and 8-13% for pH.However,the loci identified for fruit weight did not explain more than 10%of the phenotypic variance.We also reported the association between fruit quality traits and metabolites detected by Proton nuclear magnetic resonance analysis directly responsible for these fruit quality traits.Organic acids,citric acid,and quinic acid were significantly(P<0.05)and positively correlated with titratable acidity.Sugar molecules showed a strong and positive correlation with total soluble solids.Overall,the study dissected the genetic basis of fruit quality traits and established an association between these fruit quality traits and metabolites.