High density genetic map and quantitative trait loci(QTLs)associated with petal number and flower diameter identified in tetraploid rose

Rose is one of the most important ornamental and economic plants in the world.Modern rose cultivars are primarily tetraploid,and during meiosis,they may exhibit double reduction or preferential chromosome pairing.Therefore,the construction of a high density genetic map of tetraploid rose is both challenging and instructive.In this study,a tetraploid rose population was used to conduct a genetic analysis using genome sequencing.A total of 17382 single nucleotide polymorphism(SNP)markers were selected from 2308042 detected SNPs.Combined with 440 previously developed simple sequence repeats(SSR)and amplified fragment length polymorphism(AFLP)markers,a marker dosage of 6885 high quality markers was successfully assigned by GATK software in the tetraploid model.These markers were used in the construction of a high density genetic map,containing the expected seven linkage groups with 6842 markers,a total map length of 1158.9 c M,and an average inter-marker distance of 0.18 c M.Quantitative trait locus(QTL)analysis was subsequently performed to characterize the genetic architecture of petal number and flower diameter.One major QTL(qpnum-3-1)was detected for petal number in three consecutive years,which explained 20.18–22.11%of the variation in petal number.Four QTLs were detected for flower diameter;the main locus,qfdia-2-2,was identified in two consecutive years.Our results will benefit the molecular marker-assisted breeding of modern rose cultivars.In addition,this study provides a guide for the genetic and QTL analysis of autotetraploid plants using sequencing-based genotyping methods.

In the name of the rose:a roadmap for rose research in the genome era

The recent completion of the rose genome sequence is not the end of a process,but rather a starting point that opens up a whole set of new and exciting activities.Next to a high-quality genome sequence other genomic tools have also become available for rose,including transcriptomics data,a high-density single-nucleotide polymorphism array and software to perform linkage and quantitative trait locus mapping in polyploids.Rose cultivars are highly heterogeneous and diverse.This vast diversity in cultivated roses can be explained through the genetic potential of the genus,introgressions from wild species into commercial tetraploid germplasm and the inimitable efforts of historical breeders.We can now investigate how this diversity can best be exploited and refined in future breeding work,given the rich molecular toolbox now available to the rose breeding community.This paper presents possible lines of research now that rose has entered the genomics era,and attempts to partially answer the question that arises after the completion of any draft genome sequence:‘Now that we have“the”genome,what’s next?’.Having access to a genome sequence will allow both(fundamental)scientific and(applied)breeding-orientated questions to be addressed.We outline possible approaches for a number of these questions.