Two-year-old, container-grown `Misty' southern highbush blueberry plants were sprayed to drip with two concentrations of hydrogen cyanamide (HCN) (20.4 g·L–1 and 10.2 g·L–1) after exposure to 0, 150, or 300 hr of continuous chilling at 5.6°C. All plants were sprayed immediately after chilling and placed in a greenhouse for several weeks. The plants were moved outdoors during flowering to increase cross-pollination from nearby `Sharpblue' blueberry plants. HCN sprays killed some of the more advanced flower buds on shoot terminals and on small-diameter wood from the previous spring growth flush. Significantly greater flower bud mortality occurred for the 20.4 g·L–1 HCN sprays than for the 10.2 g·L–1 sprays. Flower buds subjected to 0 hr of chilling were more susceptible to spray burn than flower buds receiving 150 or 300 hr of chilling. Very little flower bud death occurred with the 10.2 g·L–1 HCN rate on plants receiving 300 hr of chilling. Vegetative budbreak was advanced for both HCN treatments compared to controls, regardless of chilling treatment. HCN-treated plants were heavily foliated at full bloom, while non-treated plants had very few to no leaves during bloom. HCN may be useful for stimulating vegetative growth in some southern highbush blueberry cultivars that suffer from poor foliation during flowering and fruit set.
J.G. Williamson and R.L. Darnell
D. Scott NeSmith and Arlen D. Draper
A new southern highbush blueberry cultivar named `Camellia' was released in 2005 by The University of Georgia and the USDA–ARS. `Camellia' is a hybrid containing mostly Vaccinium corymbosum and a small amount of V. darrowi. The new cultivar was selected in 1996 at the Coastal Plain Experiment Station in Tifton, Ga. from a cross of MS-122 × MS-6, and was tested as TH-621 in plantings at Alapaha, Ga. beginning in 1998. `Camellia' has an estimated chill requirement of 450 to 500 hours (<7 °C). It is an early- to mid-season cultivar, having berries that are large, with a very light blue color, and a small, dry picking scar. Berry firmness is good and flavor is very good. `Camellia' flowers 5 to 8 days after `Star' and `O'Neal' in south Georgia, and ripens 4 to 9 days after `Star', and with `O'Neal'. Plants are highly vigorous, with strong cane growth and an open, upright bush habit and a narrow crown. Yields have been similar to `Star' and greater than `O'Neal'. `Camellia' should be planted with other southern highbush blueberry cultivars with a similar time of bloom for cross-pollination (`Star' and `O'Neal' suggested). It is recommended on a trial basis at this time. `Camellia' requires a license to propagate. For licensing information and/or a list of licensed propagators, contact the Georgia Seed Development Commission, 2420 S. Milledge Avenue, Athens, GA 30606; or visit their website at www.gsdc.com.
D. Scott NeSmith
A new southern highbush blueberry cultivar named `Rebel' was released in 2005 by The University of Georgia. It is a very early season cultivar with large fruit having a medium to light blue color, and a small, dry picking scar. `Rebel' berry firmness is good, while flavor is only average. The new cultivar flowers 3 to 4 days before `Star' and ripens 6 to 9 days before `Star' in south and middle Georgia. `Rebel' plants are highly vigorous, very precocious and have a spreading bush habit with a medium crown. Yield has been similar to or greater than `Star' in south Georgia. Leafing has been excellent, even following mild winters. Rebel has an estimated chill requirement of 400 to 450 hours (<7 °C). Propagation is very easily accomplished using softwood cuttings. Plants of `Rebel' are self-fertile to a degree, but should be planted with other southern highbush blueberry cultivars with a similar time of bloom for cross-pollination (`Emerald' and `Star' suggested). `Rebel' is new, so planting on a trial basis is recommended. `Rebel' requires a license to propagate. For licensing information and/or a list of licensed propagators, contact the Georgia Seed Development Commission, 2420 S. Milledge Avenue, Athens, GA 30606; or visit their web-site at www.gsdc.com.
Sarah K. Taber and James W. Olmstead
of 13 potted, greenhouse-grown southern highbush blueberry cultivars after cross- and self-pollination in 2012 and 2013. Canes on single plants were divided between cross- or self-pollination treatments, and 120 individual flowers were hand
C. L. Gupton, J. M. Spiers, and A. D. Draper
Eight clones with various Vaccinium species in their background were evaluated to determine their potential for improving fruit characteristics in the southern highbush blueberry. One clone was crossed with each of the others to produce seven sets of progenies which were evaluated with the parent clones. Heritability estimates were computed as the regression of progeny on parental means for each character. The progenies ranged from small to average berry size and weight, were above average for picking scar, and were generally less than average for color, firmness, and flavor. Mean of progenies was not significantly different from the parental mean for any character. Very high (0.45-0.85) heritability estimates were found for each character except berry firmness (0.22). These results suggest that considerable improvement in each character except possibly berry firmness should result from phenotypic recurrent selection in a broad based population involving these parents.
Manjula Carter, John R. Clark, and Mike Phillips
The southern highbush blueberry is a hybrid of Vaccinium corymbosum L. and one or more southern-adapted Vaccinium species. The southern highbush is advantageous to blueberry growers in the South since its fruit ripen 1 to 4 weeks in advance of traditional rabbiteye (V. ashei Reade) cultivars. Only limited research has been done on cultural aspects of southern highbush production. The objective of this study was to determine the optimum nitrogen rate for the southern highbush blueberry. A planting of pine straw-mulched `Cape Fear' blueberry was established in 1994 at the Southwest Research and Extension Center, Hope, Ark. Nitrogen rate treatments (0, 67, 134, 202, 269 kg·ha-1 N) were applied annually over a 3-year period (1997-99) with urea as the N source. Soil samples were taken prior to N fertilization to determine if N applied the previous year influenced current soil analysis values. Foliar elemental composition, fruit yield and individual berry weight were also determined for each treatment. Soil analysis indicated that the carryover effect of N applications from previous years was minimal. However, a possible decline in soil pH, Ca, and Mg over time at the higher N rates indicated that these variables should be closely monitored. No consistent relationship was evident between N application rate and soil nitrate. Nitrogen application rate did not have any consistent impact on yield, berry weight or foliar elemental composition. However, based on foliar N, the data indicate that N rates of 67-134 kg·ha-1 N are adequate for southern highbush in mulched culture.
D. Scott NeSmith
Southern highbush blueberries (interspecific hybrids containing mostly Vaccinium corymbosum L.) have gained a significant share of the production acreage of commercial blueberries in Georgia in recent years. A major reason for the interest in the
D. Scott NeSmith and Mark K. Ehlenfeldt
‘Blue Suede™’ is a new southern highbush blueberry ( Vaccinium hybrid) jointly released by the University of Georgia College of Agricultural and Environmental Sciences, the University of Georgia Agricultural Experiment Station, and the U
John R. Clark and Robert Bourne
The southern highbush blueberry (Vaccinium spp.) `Blueridge', `Cape Fear', `Cooper', `Georgiagem', `Gulf Coast', and `O'Neal'; the rabbiteye (V. ashei Reade) `Climax'; and the highbush (V. corymbosum L.) `Bluecrop' were evaluated for ovary damage following exposure of flower buds to 0 to 30C in a programmable freezer in Dec. 1993 and Jan. and Feb. 1994. The plants sampled were growing at the Univ. of Arkansas Fruit Substation, Clarksville. Damage was based on oxidative browning of the ovaries following an incubation period after removal from the freezer. With the exception of `Climax', a minimum temperature of –15C was required before bud damage was sufficient enough to differentiate among cultivars. All southern highbush cultivars and `Bluecrop' had superior hardiness compared to `Climax' at –15C in December, –20C in January, and –15C in February. Maximum hardiness of all cultivars was found in January. The hardier southern highbush cultivars were `Cape Fear' and `Blue Ridge'. Less hardy cultivars were `Gulf Coast, `Cooper', `Georgiagem', and `O'Neal', although the date of sampling affected the ranking of these clones for hardiness, especially for the February sample date. `Bluecrop' was not consistently hardier than the hardier southern highbush cultivars, except at the February sample date.
Donna A. Marshall*, Stephen J. Stringer, and James M. Spiers
A study was initiated in November, 2002 to determine the effects of exposing two Southern Highbush blueberries (Vaccinium corybosum L) to artificial chilling hours on initiation of bud break and advancement of floral and vegetative bud maturity. Plants of `Jubilee' and `Misty' were divided into 2 groups in which one was left outdoors, allowing chilling to occur and accumulate naturally, while the other group was placed in a growth chamber set at a constant artificial temperature of 4 °C. Five plants of each cultivar were then placed into a heated greenhouse after 0, 200, 400, 600, or 800 hours of chilling (total hours of exposure to <5 °C) had accumulated for forcing of flower bud development. The progression of floral bud development of the terminal three buds on five tagged stems was observed at 7-10 day intervals for 30 days. At the end of the forcing period observations were also made on total percent vegetative and floral bud break. Prior to accumulating sufficient chilling requirements, chilling delivery method did not appear to influence the rate of floral bud development since none advanced past stage 3 regardless of chilling regime used. However after chilling requirements were met, flower buds of plants that were allowed to chill naturally developed more quickly than did those chilled by artificial means.