Identification and validation of microsatellite markers in strawberry tree (Arbutus unedo L.)

Abstract

Strawberry tree (Arbutus unedo L.), an evergreen shrub/small tree of the family Ericaceae, is a main constituent of theMediterranean basin flora; although it is also found in southwestern France, Macaronesia, and Ireland. The small fruits are ediblebut mostly used for preparation of preserves and jams, and for liquors such as the Portuguese traditional “aguardente de medronho”.Traditionally cultivated by small farmers, often in consociation with Quercus sp., strawberry tree is presently emerging as a newimportant fruit crop cultivated in large orchards by modern export-oriented enterprises. This change of paradigm requires a growingrole of plant breeding, upstream of the production process. Genomic tools for this species are mostly limited to the chloroplast genomesequence and to genomic data described in this work. In order to identify strawberry tree microsatellite (SSR) loci we performed partialgenome next-generation sequencing using the Ion Torrent technology. The sequenced ~24.6M nucleotides resulted in the identificationof 1185 microsatellite markers mostly constituted by dinucleotide motifs. The relative amount of microsatellite dinucleotide motifs (AG/CT – 71.7%, AC/GT – 20.5%, AT/AT – 2.9%, and CG/CG – 0.3%) is similar to the one observed in other Ericaceae species. Among atested sample of 40 SSR primer pairs, 20 amplified well-defined PCR products, 12 (30%) were validated as polymorphic. Used in ourcollaborative project for molecular identification of selected and improved clones, the identified SSR loci constitute a strong tool for alarge panoply of applied and fundamental studies of this emerging fruit crop.