Identification of Sparkleberry (Vaccinium Arboreum) Genome Introgression with Microsatellite Markers Developed in Highbush Blueberry

Sparkleberry (VA, Vaccinium arboreum Marsh.) is a wild blueberry species that has been used in southern highbush blueberry (SHB, Vaccinium corymbosum L. hybrids) breeding as a source of genetic traits for soil adaptation and amenability to mechanical harvest. One of the primary limitations for trait introgression from VA has been difference in ploidy level with cultivated SHB. However, chromosome duplication of several VA genotypes by colchicine treatment has allowed direct crosses with SHB, resulting in several thousand hybrid seedlings available for evaluation. Currently, hybrid seedlings are identified by several phenotypic characteristics. Identification of VA specific alleles from microsatellite markers that amplify in both species would provide a rapid method of positively identifying seedlings where VA genome introgression has occurred.  Twelve unrelated tetraploid VA seedlings that comprise the majority of founding clones in the current VA introgression project were genotyped with a set of 13 microsatellite markers previously used to genotype SHB cultivars and advanced selections from the University of Florida blueberry breeding program. Twelve of the 13 markers (92%) consistently amplified microsatellite loci in VA; 11 markers amplified a single locus. When both SHB and VA were considered, the number of alleles per marker ranged from one to 17.  Of those markers, the number of alleles per marker that were only found in VA ranged from zero to 13.  Two of the 12 markers amplified only unique alleles in the limited set of VA genotypes assayed and when used in combination with an additional highly polymorphic marker allowed identification of VA introgression in early generations of crosses.