Sixty-nine accessions representing wild and domesticated highbush blueberry (Vaccinium corymbosum L.) germplasm were genotyped using 28 simple sequence repeats (SSRs). A total of 627 alleles was detected and unique fingerprints were generated for all accessions. Suspected duplicate accessions of `Coville' and `Ivanhoe' had DNA fingerprints that were identical to `Coville' and `Ivanhoe', respectively. Genetic similarity measures placed wild and cultivated blueberries in separate groups. Northern highbush blueberries grouped among ancestral clones that were used extensively in blueberry breeding such as `Rubel' and `Stanley'. Southern highbush blueberries formed a separate group from northern highbush blueberries. The microsatellite markers used here show excellent promise for further use in germplasm identification, in genetic studies of wild Vaccinium L. populations, and for constructing linkage maps.
Peter Boches, Nahla V. Bassil, and Lisa Rowland
Peter Boches, Brooke Peterschmidt, and James R. Myers
One hundred S. l. var. cerasiforme (Dunal) accessions from the ‘Tanksley’ designated core collection were evaluated for horticultural quality under greenhouse conditions. Fourteen selected accessions were grown under field conditions in a replicated trial to evaluate the fruit for phenolic content. Total fruit phenolics ranged from 44 to 82 mg/100 g gallic acid equivalents (GAE) fresh weight (FW) as measured by Folin-Ciocalteau assay (F-C), and 12 to 108 mg/100 g FW as measured by high-performance liquid chromatography (HPLC). Five accessions (LA1712, LA1455, LA2633, LA1668, and LA2632) had significantly higher total phenolics (F-C) than cultivars (P ≤ 0.05). These five accessions also possessed interesting phenolics profiles, including high levels of caffeoylquinic acids (LA1620, LA1455, and LA2633) and rutin (LA2633).
Peter J. Mes, Peter Boches, James R. Myers, and Robert Durst
Cultivated tomatoes (Solanum lycopersicum L.) produce anthocyanins in vegetative tissues and certain flavonols can be found in the fruit. Some related wild species do produce anthocyanins in the fruit, and this trait has been transferred into cultivated tomato. Fruit with the genes Abg, Aft, and atv exhibit varying degrees of anthocyanin production in the epidermis, but not in the fruit pericarp. Fruit with these alleles in various combinations were analyzed to characterize the anthocyanidin profile, moieties, and total anthocyanin content. In general, combining atv with either Aft or Abg substantially increased anthocyanin production in the fruit. Over 23 different anthocyanins were detected, petunidin-3-(p-coumaryl)-rutinoside-5-glucoside being predominant. The highest level of anthocyanin expression was observed in small fruit with the genotype Abg- atvatv and AftAft atvatv, well in excess of 100 mg/100 g fresh weight of epidermis and subepidermis depending on the size of the fruit. Nonanthocyanin flavonoids were also upregulated in proportion to the anthocyanin concentration. The anthocyanin genes were also combined with genes affecting carotenoid composition and content. Reduced carotenoid content conditioned by the alleles B (Beta) and r (yellow flesh) was associated with lower total anthocyanins, an unexpected observation because the carotenoid and anthocyanin pathways are thought to be independent. The level of anthocyanin did not affect carotenoid profiles or amounts.
Peter Boches, Lisa J. Rowland, Kim Hummer, and Nahla V. Bassil
Microsatellite markers for blueberry (Vaccinium L.) were created from a preexisting blueberry expressed sequence tag (EST) library of 1305 sequences and a microsatellite-enriched genomic library of 136 clones.
Microsatellite primers for 65 EST-containing simple sequence repeats (SSRs) and 29 genomic SSR were initially tested for amplification and polymorphism on agarose gels. Potential usefulness of these SSRs for estimating species relationships in the genus was assessed through cross-species transference of 45 SSR loci and cluster analysis using genetic distance values from five highly polymorphic EST-SSR loci. Cross-species amplification for 45 SSR loci ranged from 17% to 100%, and was 83% on average in nine sections. Cluster analysis of 59 Vaccinium species based on genetic distance measures obtained from 5 EST-SSR loci supported the concept of V. elliotii Chapm. as a genetically distinct diploid highbush species and indicated that V. ashei Reade is of hybrid origin. Twenty EST-SSR and 10 genomic microsatellite loci were used to determine genetic diversity in 72 tetraploid V. corymbosum L. accessions consisting mostly of common cultivars. Unique fingerprints were obtained for all accessions analyzed. Genetic relationships, based on microsatellites, corresponded well with known pedigree information. Most modern cultivars clustered closely together, but southern highbush and northern highbush cultivars were sufficiently differentiated to form distinct clusters. Future use of microsatellites in Vaccinium will help resolve species relationships in the genus, estimate genetic diversity in the National Clonal Germplasm Repository (NCGR) collection, and confirm the identity of clonal germplasm accessions.