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  • Author or Editor: D. Scott NeSmith x
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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.

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A postharvest 1-methylcyclopropene (1-MCP) treatment was evaluated for its ability to maintain firmness and delay the ripening of rabbiteye blueberries. Three cultivars, Austin, Brightwell, and Premier, were harvested by hand from the UGA Alapaha Blueberry Farm and treated overnight with 1 μL·L−1 1-MCP as field heat was being removed [0 to 1 °C, 90% to 95% relative humidity (RH)]. Fruit were evaluated for firmness, total soluble solids (TSS), total acidity (TA), ethylene production, and other quality attributes at 0, 1, and 2 weeks after harvest as well as 1 or 4 days post-removal evaluations at room temperature (≈21 °C). In general, the 1-MCP treatment resulted in the stimulation of ethylene production in all three cultivars but had minimal effect on TSS and TA content. Furthermore, the treatment resulted in an accelerated loss of firmness in ‘Brightwell’. The lack of inhibition of fruit ripening likely related to the fact that blueberries were harvested, and subsequently treated with 1-MCP, at a post-climacteric stage of development. Based on current results, more information is required regarding ethylene production during rabbiteye blueberry fruit maturation before establishing a 1-MCP treatment recommendation for use by the rabbiteye blueberry industry.

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During 1998 and 1999, `Genesis' triploid watermelons [Citrullus lanatus (Thunb.) Matsum. & Nak.] were grown in large blocks with a single row of the diploid `Ferarri' planted as a pollinizer in the middle. A once-over harvest each year was made in harvest lanes 0, 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 m perpendicular distances from the pollinizer row. Individual fruit were weighed and counted. Data from both years indicated a similar distribution of triploid fruit with respect to distance from the pollinizer row. The greatest number of triploid fruit per unit land area was in the harvest row 3.0 m from the pollinizer row. When distance from the pollinizer row was 6.0 m or greater, triploid fruit numbers diminished substantially. Yield estimates made each year using the fruit density data suggested that a 1 pollinizer: 4 triploid ratio gave the maximum total triploid fruit yield per hectare for 1.5-m row spacings. These results should prove useful in designing field planting strategies to optimize triploid watermelon production.

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Plants of the rabbiteye blueberry (Vaccinium ashei Reade) cultivars Brightwell, Climax, and Tifblue were subjected to pollination with bees or to applications of 250 mg·L-1 of gibberellic acid (GA3) to examine the influence on fruit size and maturation period. Plants were thinned to a similar fruit density (FD) 4 weeks after anthesis. `Tifblue' and `Climax' fruit were smaller on GA3-treated than on bee-pollinated plants, but no difference was observed for `Brightwell'. The fruit maturation period for `Climax' was not affected by treatments, but `Brightwell' and `Tifblue' fruit on pollinated plants ripened 2 weeks earlier than fruit on GA3-treated plants. These data suggest that excess fruit load is not the primary factor responsible for the smaller fruit size and lengthened fruit development period resulting from GA3 applications to rabbiteye blueberries.

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Rabbiteye blueberries (Vaccinium ashei Reade) often exhibit poor fruit set under commercial field conditions. Problems of low fruit set have been attributed to short periods of flower receptivity in different fruit crops. This study seeks to establish the effective pollination period (EPP, defined as the number of days during which pollination is effective to produce a fruit) in rabbiteye blueberry. The cultivars Brightwell and Tifblue were chosen due to their known difference in fruit set and field performance. Flowers were hand pollinated 0, 2, 4, 6, and 8 days after anthesis (DAA) using self- and cross-pollen. Fruit set, seeds per berry, berry weight and days to ripening were recorded. Fruit set showed a polynomial trend across flower ages. `Brightwell' was highly receptive from the day of anthesis, whereas, `Tifblue' receptivity was low until 2 DAA. `Brightwell' and `Tifblue' flowers produced adequate fruit set (≥50%) over a period of 7 and 5 days, respectively. In `Tifblue', fruit set was limited by the low receptivity of newly opened flowers. The difference in EPP helps to explain the performance of these cultivars in the field. The rate of ripening increased with flower age in both cultivars. The number of seeds per berry was affected by flower age only in `Tifblue'. The effect of flower age on berry weight depended on the cultivar and the pollen source.

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During 1998 and 1999, `Genesis' triploid watermelons were grown in large blocks with a single row of the diploid `Ferarri' planted as a pollinizer in the middle. A once-over harvest of triploid watermelons was made each year in harvest lanes 0-, 1.5-, 3.0-, 4.5-, 6.0-, 7.5-, and 9.0-m perpendicular distances from the pollinizer row. Individual fruit were weighed and counted. Data from both years indicated a similar distribution of triploid fruit with respect to distance from the pollinizer row. The greatest number of triploid fruit per unit land area was in the harvest row 3.0 m from the pollinizer row. When distance from the pollinizer row was 6.0 m or greater, triploid fruit numbers diminished substantially. Yield estimations made each year using the fruit density data suggested that a 1 pollinizer: 4 triploid ratio gave the maximum total triploid fruit yield per hectare for 1.5-m row spacings. These results should prove useful in designing field planting strategies that seek to optimize triploid watermelon production.

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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.

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Rabbiteye blueberry (Vaccinium ashei Reade) is a bee-pollinated small fruit crop that often exhibits poor fruit set. Mixed cultivar plantings are recommended because cross-pollination is required for optimum yields, and bees are expected to transfer pollen from one cultivar to another. The objective of this study was to assess transport of cross-pollen by bumblebees in a rabbiteye blueberry planting. Experiments were conducted in 2003 and 2004 in a plot composed of `Brightwell' and `Climax' plants arranged in alternating rows. The proportion of `Brightwell' and `Climax' pollen carried on the bodies of bumblebees was estimated based on frequency distributions of pollen diameter, measured with a particle counter. About 75% of bumblebees collected in 2003 carried <20% cross-pollen. Proportions of cross-pollen in 2004 were higher than in 2003, but still, about 85% of bumblebees collected carried <40% cross-pollen. The proportion of cross-pollen carried by bumblebees changed during the flowering season. The greatest likelihood for cross-pollination occurred during the time of maximum bloom overlap, although the median proportion of cross-pollen was not >30% on any sampling day of 2004. The results from this study emphasize the need to select more self-fertile rabbiteye blueberry cultivars and to maximize bloom overlap in blueberry plantings.

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Blueberries are bee-pollinated species that benefit from cross-pollination. Cross-pollination is particularly critical for optimum fruit set of rabbiteye blueberries (Vaccinium ashei Reade) because of their limited degree of self-fertility. In order to determine if the failure to set adequate commercial fruit loads is due to a lack of cross-pollination, research was needed to establish how much out-crossing rabbiteye blueberry pollinators actually do. A novel method was developed to identify pollen grains on the bodies of bumblebees by cultivar. The technique discriminates between two cultivars, based on differences in pollen diameter. Bumblebees were collected in a plot composed of blueberry plants of the cultivars Brightwell and Climax since these cultivars produce pollen of different size. Pollen loads of bumblebees contained low proportions of cross-pollen regardless of the cultivar they were visiting. Data suggest that inadequate levels of cross-pollination play a major role in low fruit set problems of rabbiteye blueberry. The composition of bees' pollen load changed with the phenology of the crop. The greatest likelihood for cross-pollination occurred around the time of maximum bloom overlap. Bumblebees foraging on `Brightwell' flowers carried more total blueberry pollen and a higher proportion of self-pollen than those visiting `Climax'. This may be due to differences in pollen release between flowers of these two cultivars.

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