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
J.R. Clark, D. Creech, M.E. Austin, M.E. Ferree, P. Lyrene, M. Mainland, D. Makus, L. Neuendorff, K. Patten, and J. Spiers
Highbush (Vaccinium corvmbosum L.) rabbiteye (V. ashei Reade) and southern highbush (Vaccinium spp.) blueberries grown at seven locations in six southern states were sampled in 1988 and 1989 to determine foliar elemental levels among blueberry cultivars and types. Across locations, elemental levels of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu and Al were similar for highbush and southern highbush types. Rabbiteye elemental levels were different from highbush and southern highbush for N, P, K, Ca, S, Mn, Cu and Al. The findings indicate that similar standard foliar levels can be used for highbush and southern highbush blueberries in determining nutritional status of plantings by foliar analysis. Rabbiteye blueberries appear to have different foliar levels, and may require species-specific standards for nutritional monitoring of plantings.
Creighton L. Gupton and James M. Spiers
An experiment arranged in a randomized complete block design with four replications of two cultivars × six pH levels × four Zn levels was conducted to determine if Zn caused leaf chlorosis in rabbiteye (Vaccinium ashei Reade cv. Climax) and southern highbush (mostly V. corymbosum L. cv. Bladen) blueberry. `Bladen' accumulated more foliar Mn and Zn than `Climax', but Fe concentration was similar in the two cultivars. Leaf chlorosis ratings were similar for the two cultivars. Solution pH had no significant effect on Mn, Zn, or Fe leaf concentration or degree of chlorosis. Zinc level in the nutrient solution affected leaf concentration of Mn and Zn but not of Fe. A significant linear increase in chlorosis resulted from increasing Zn solution concentration from 30 to 120 mg·L–1. We conclude that high levels of Zn may induce leaf chlorosis in rabbiteye and southern highbush blueberry.
Yu Hong, D. Creech, Wang Chuanyong, Gu Yin, and He Shanan
Blueberries are now the hot point of fruit development in China. Researches conducted in the past since 1980s include mainly introduction and propagation. More than 30 cultivars of rabbiteye blueberries and southern highbush blueberries were introduced successfully in the Nanjing Botanical garden in late 1980s. For dormant cuttings of 4 rabbiteye blueberry cultivars Gardenblue, Tifblue, Climax, and Premier the rooting percentage could reach 84%, 52%, 62%, and 79% respectively under interrupted misting. Lignification of the cuttings seemed the key point for rooting. For soft cuttings the rooting percentage can reach 90% to 95% with chemical treatments. Seedling selection has been conducted and some promising individuals are under observation. So far, there were little experiments on cultural practice under taken. But looking at the difference of soils between the blueberry growing areas in the US and China it seems that there are a series of aspects should be researched in the future.
S.J. Stringer, J.M. Spiers, and A.D. Draper
Two new southern highbush blueberry cultivars, `Dixieblue' and `Gupton', will provide growers with new blueberry cultivars having excellent fruit quality that ripen relatively early in the season, during the profitable early fresh-market window. Berries of `Dixieblue' are light blue, medium in size, and their flat shape makes them most attractive. `Gupton' is very productive and berry quality is also excellent. The performance of these cultivars represent an improvement over most currently available southern highbush blueberry cultivars due to 1) their durability and performance on both upland and sandy soils endemic to the Gulf Coast and 2) consistent production of high quality fruit that will meet the demand for early ripening fresh-market blueberries. The new rabbiteye blueberry cultivar, `DeSoto', represents an improvement over currently available rabbiteye blueberry cultivars for late-season production. `DeSoto' produces medium-to-large fruit having excellent color, flavor, and firmness Plants of `DeSoto' are productive, vigorous but semi-dwarf, upright and spreading. It's semi-dwarf growth habit, which is unique among currently grown rabbiteye blueberries, results in bushes that attain a maximum height of about 2 meters upon maturity, reducing the necessity of top-pruning that is required for all other cultivars. `DeSoto' blooms two to three weeks later than early-to-mid season cultivars such as `Climax' and `Tifblue', providing insurance against late-spring freezes. Similarly, its fruit mature 21 to 14 days or more, respectively after these same cultivars. `DeSoto' will provide niche market blueberry growers with a new cultivar having productivity, plant vigor, fruit quality, and very late ripening period that will extend their marketing season. The new evergreen ornamental blueberry, `Native Blue', is low growing, compact and finely branched with small glaucous leaves, traits that are quite typical of V. darowii. `Native Blue' has beautiful foliage that changes color in different seasons. Mature leaves are darker green while newer growth exhibits a light pinkish hue that changes to a bluish green. Other desirable characteristics of `Native Blue' are its dwarf growth habit, hardy and vigorous growth, and its capacity for a high level of fruit production that serves as an attractant to birds and other wildlife. `Native Blue' will provide southeastern U.S. nurserymen, landscapers, and homeowners with a novel and beautiful new ornamental shrub that will complement plantings of azaleas, camellias, crepe myrtles, etc.
Ena Akamatsu, Takanori Kai, Hideaki Hirabaru, Chizuko Yukizaki, Miho Sakai, Hirofumi Uto, Hirohito Tsubouchi, and Hisato Kunitake
Blueberry (Vaccinium sp.) fruits contain high concentrations of polyphenols such as anthocyanin. It is well known that polyphenols have antioxidant activity, so it is likely that the fruit has a possible preventative effect against several diseases like cancer. However, only a few reports so far have studied the human health benefits of the leaves. In this study, the antioxidant activity and antiviral effects of blueberry leaves were investigated. The leaves of three groups of blueberry, northern highbush blueberry (NHB), southern highbush blueberry (SHB), and rabbiteye blueberry (REB), were examined. These leaves were harvested in July and extracted with 80% ethanol. Samples were analyzed for antioxidant activity (DPPH radical scavenging activity) and antiviral activity against hepatitis C virus using the replicon cell assay (Lomann et al., 1999). The antioxidant activity showed significant variability between cultivars and species, with REB having about two times the activity of NHB and SHB. Antiviral activity was observed in the extracts of the leaves and the fruit, and the activity of the leaves was higher than that of the fruit. Among the cultivars and species evaluated, the antiviral activity of REB was higher than that of NHB and SHB. In addition, we discovered a positive correlation (r=0.68) between the antioxidant activity and the antiviral activity, using the leaves of hybrid seedlings of REB. Therefore, it is possible to speculate that the antiviral activity bears some relation to the antioxidant activity.
D. Scott NeSmith and Gerard Krewer
Leaf bud development is a problem on many blueberry cultivars grown throughout the Southeast. Dormex (50% hydrogen cyanamide) has shown potential in accelerating leaf and floral bud development of some fruit crops, but its usage on blueberries has not been thoroughly explored. A greenhouse experiment was conducted to examine the effects of timing Dormex applications on `Climax' rabbiteye blueberry (Vaccinium ashei) and `Oneal' southern highbush blueberry (V. corymbosum). Plants were subjected to low and moderate chilling conditions and were forced under greenhouse conditions. Dormex timings were: 1)1 day after forcing (DAF), 2) 3 DAF, 3) at 10% stage 3 floral buds, 4) at 30% to 50% stage 3 floral buds, 5) at 10% to 30% stage 4 floral buds, 6) control (no Dormex). All Dormex applications were applied at a rate of 2% product. Results showed that Dormex both increased and accelerated leaf bud break as compared to the control. However, flower buds at stage 3 of development or beyond were very susceptible to chemical burn by the product. The data indicate that timing of Dormex applications on blueberries should be based on rate of plant development rather than calendar time. Additional research is needed to most effectively use the product to aid blueberry leaf development.
Mark K. Ehlenfeldt and James J. Polashock
The primary gene pool of Vaccinium species used by blueberry breeders has traditionally been the North American Vaccinium species of section Cyanococcus. Blueberries in commercial production represent three primary Vaccinium species and two ploidy levels. Significant use has been made of the secondary gene pool of Vaccinium, especially in the development of southern highbush blueberry (Vaccinium ×corymbosum) cultivars. Section Hemimyrtillus species are distantly related and are best considered part of the tertiary gene pool of Vaccinium. Vaccinium padifolium, a member of section Hemimyrtillus and native to the Madeira Islands, Portugal, has features of notable value to conventional blueberry development, among these: upright structure, strong growth, abundant flowering and fruiting, good self-fertility, inflorescence structure suited to mechanical harvesting, and indeterminate/repeat flowering. Our objective was to incorporate germplasm from this section into cultivated materials and transfer the desirable traits these species possess for commercial production. We used V. padifolium as a female in crosses with V. corymbosum and generated two highly fertile hybrids. These hybrids are intermediate in morphology, phonological, and their hybridity has been confirmed through DNA testing. These hybrids were used in further crosses to a variety of section Cyanococcus selections and have generated numerous second-generation hybrids. We have also determined by flow cytometry the ploidy levels of the hybrids and several previously unevaluated section Hemimyrtillus species.
Y.H. Huang, G.A. Lang, C.E. Johnson, and M.D. Sundberg
Five-year old `Sharpblue' southern highbush blueberry plants (Vaccinium corymbosum L.) were self- and cross-pollinated (`O'Neal') to study peroxidase (POD) activity, isozyme patterns, and histological localization during fruit development. Cross-pollination resulted in larger and earlier-ripening fruit. Activities of soluble and bound POD were very high during fruit growth period I, with peaks at 10 and 20 days after self- and cross-pollination. Activity was much higher for cross-pollinated fruit. During fruit growth period II, POD activities were low in both pollination treatments. During ripening, soluble POD increased, then declined in both treatments. Bound POD activities increased during the color transition from blue to dark blue, with the increase greater in self-pollinated fruit. Banding patterns of soluble and bound POD isozymes and their histological localization varied by pollination treatment as well as fruit developmental stage. During fruit ripening, soluble POD activity appeared to be associated with color transition from light blue to blue, while bound POD activity appeared to be associated with color transition from blue to dark blue.
Donna A. Marshall, J.M. Spiers, K.J. Curry, and S.J. Stringer
Fruit splitting takes place in rabbiteye and southern highbush blueberries when a preharvest rainfall occurs and when fruit are fully ripe or approaching full ripeness. This study was initiated to develop a laboratory method to identify the rain-related incidence of splitting in cultivated blueberries. Multi-year field surveys of select rabbiteye and southern highbush cultivars show that the incidence of rain-related splitting is strongly cultivar dependent. Year to year variations within cultivars reflected yearly differences in ripening times and amounts and timing of rainfall. Laboratory values of forced splitting and field splitting data of three years show a strong correlation indicating that the incidence of fruit splitting can be accurately estimated by laboratory methods. Soaking the berries in distilled water 14 hours at room temperature gives a confident determination of splitting tendencies. Blueberry breeders can use this method to evaluate new potential blueberry cultivars for splitting tendencies. This laboratory method could also be used by geneticists to test selections accurately for splitting tendencies as part of routine screening. This can lead to a long-term goal of reducing splitting susceptible blueberries in commercial plantings.