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Stephen J. Stringer, Arlen D. Draper, Donna Marshall-Shaw, Blair J. Sampson, and John J. Adamczyk Jr.

Southern Horticulture Laboratory in Poplarville, MS, from a cross of T142 × ‘Powderblue’. T142 resulted from a cross of ‘Tifblue’ × ‘Woodard’ and was selected in the early 1960s at Tifton, GA in the University of GA blueberry breeding and genetics research

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Dongliang Qiu, Xiangying Wei, Shufang Fan, Dawei Jian, and Jianjun Chen

global market analysis. U.S. Highbush Blueberry Council, Folsom, CA Brevis, P.A. Bassil, N.V. Ballington, J.R. Hancock, J.F. 2008 Impact of wide hybridization on highbush blueberry breeding J. Amer. Soc. Hort. Sci. 133 427 437 Callow, P. Haghigh, K

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Mark K. Ehlenfeldt, James J. Polashock, Allan W. Stretch, and Matthew Kramer

1 To whom reprint requests should be addressed: P.E. Marucci Center for Blueberry and Cranberry Research, 125A Lake Oswego Road, Chatsworth, NJ 08019; e-mail mehlenfeldt@ars.usda.gov . The authors thank Robert

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P. Perkins-Veazie, P. Armstrong, and J.R Clark

Firmness of blackberries greatly determines shelf life for fresh market. Firmness in blackberries appears to be due to a combination of skin toughness and internal receptacle to permit large sample size measurements. Subjective rating of fruit require consistent evaluation by raters over harvest dates and years, and is subject to fatigue error. The FirmTech2 firmness tester was developed to provide rapid compression measurements and has been successfully used in determining the firmness of cherries and blueberries. Blackberries from a large number of clones ranging in firmness from rock-hard to squishy were measured with the FirmTech2 using a deformation range of 25 to 100 g. Additionally, blackberries were placed in storage at 2, 5, and 2/20 °C to monitor effects of storage temperature on blackberry firmness. Berries were subjectively rated and then placed on the Firmtech for measurements. A comparison of firmness readings for fruit only in the “1” (firm) category was made. Differences found among fruit readings agreed with observed differences in field subjective ratings. Stored fruit that had become soft and mushy could not be statistically differentiated from firmer fruit in quantitative readings. In conclusion, the Firmtech2 allowed rapid evaluation of breeding lines before storage.

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Sylvia J. Brooks and Paul M. Lyrene

The extent of self-fertility and self-fruitfulness was studied in Vaccinium arboreum Marsh, V. darrowi Camp, and in seedlings, termed MIKs, from open-pollination of V. darrowi (section Cyanococcus) × V. arboreum (section Batodendron) F1 hybrids. The open pollinations that produced the MIKs occurred in a field containing tetraploid southern highbush selections (based largely on V. corymbosum L.), and the pollen parents of the MIKs are believed to be southern highbush selections. The MIKs that were studied had been selected for high fruit set after open pollination in the field. Both V. arboreum and V. darrowi exhibited very low self-fruitfulness and self-fertility when hand-pollinated in a greenhouse; the former produced no seedlings from more than 600 selfed flowers, and the latter produced only 13. By contrast, southern highbush clones averaged 70 seedlings per 100 pollinated flowers when selfed and 230 when crossed. Self-fertility and self-fruitfulness of the MIKs were higher than those of V. arboreum and V. darrowi but lower than those of southern highbush selections. MIK × MIK crosses gave fewer seedlings per 100 pollinated flowers (84) than highbush × highbush crosses (230), probably reflecting their hybrid ancestry. Although introduction of V. arboreum genes into southern highbush blueberry gives plants of excellent vigor and adaptation to north Florida, several generations of breeding will be needed to obtain cultivars with high fertility and berry quality.

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Chad E. Finn, James J. Luby, Carl J. Rosen, and Peter D. Ascher

Progenies from crosses among eight highbush (Vaccinium corymbosum L.), lowbush (V. angustifolium Ait.), and V. corymbosum/V. angustifolium hybrid-derivative parents were evaluated in vitro at low (5.0) and high (6.0) pH for vitality, height, and dry weight. Succinic acid and 2[N- morpholino]ethanesulfonic acid (Mes) effectively maintained pH in the medium and rhizosphere. The pH regime did not affect percent radicle emergence from seed or survival; however, percent seed germination was slightly lower at high pH. The parental general combining ability (GCA), reciprocal and maternal, but not the specific combining ability (SCA) variance components were significant for plant vitality, height, and dry weight. The GCA variance components were six to 26 times larger than the SCA variance components for the plant growth traits. Variation due to pH regime was significant for vitality and dry weight but not for plant height. The progenies of parents with high percent lowbush ancestry were taller at both pH levels than those with less such ancestry. Little variation was apparent for higher pH tolerance as measured by dry weight; however, the GCA effects suggested that the progenies of some parents performed better than others at high pH. Vaccinium angustifolium parents differed in the extent to which tolerance to high pH was transmitted. In vitro screening in concert with a traditional breeding program should be effective in improving blueberry tolerance to higher pH.

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W.A. Erb, A.D. Draper, and H.J. Swartz

Interspecific blueberry (Vaccinium spp.) progenies were examined to determine combining abilities and genetic variability for seedling root system size and shoot vigor and to establish whether a large root system is correlated with good growth when plants are grown on a mineral soil and exposed to a moderate soil water deficit. General combining ability (GCA) variance components for root system size and shoot vigor and specific combining ability variance components for shoot vigor were significant. US226, a tetraploid hybrid of V. myrtilloides Michaux × V. atrococcum Heller, had the highest GCA effect for root system size and the lowest GCA effect for shoot vigor. US75 (V. darrowi Camp × V. corymbosum L.) had the highest GCA effect for shoot vigor and was second in GCA effect for root system size. Comparison of the crosses containing G111 (V. corymbosum) with those containing G362 (V. corymbosum) indicates that selecting for the best V. corymbosum clone to start a breeding program seems as important as selecting the mineral soil-adapted parent. Root system ratings were highly correlated with total dry weight of field-grown plants (r = 0.89). The method used in this study to evaluate seedlings for root system size and shoot vigor could be used to eliminate the less vigorous plants from a population before field planting and to evaluate mineral soil adaptability.

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Paul M. Lyrene

Variation was studied within and among five Vaccinium taxa for the flower parameters corolla length, corolla aperture diameter, stigma location relative to the apex of the corolla tube, position of the anthers relative to the stigma and to the apex of the corolla, and style length. The objective was to determine whether there was enough genetic variation to breed cultivars with flower shapes that might favor pollination by a wider range of bee species. The taxa studied were cultivated rabbiteye (V. ashei Reade), cultivated southern highbush (mainly V. corymbosum L. with up to 30% introgression from V. darrowi Camp), F1 V. ashei × V. constablaei A. Gray hybrids, V. darrowi, and V. elliottii Chapm. Vaccinium elliottii flowers differed from all others in having short styles that were not exserted from the corolla tube. Vaccinium elliottii was also unusual in that the end of the anther tube extended nearly to the stigmatic surface. Vaccinium ashei corollas were longer and had smaller apertures than those of southern highbush, possibly making them less suitable for honeybee (Apis) pollination. For corolla length and aperture diameter, F1 V. ashei × V. constablaei hybrids were similar to southern highbush, indicating that V. constablaei introgression could be used to breed hexaploid cultivars with shorter, more open flowers. Large clone-to-clone variation within taxa for each flower characteristic indicates much potential for changing the shape of the blueberry flower by breeding, if the shape that maximizes fruit set can be determined.

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D. Scott NeSmith

Southern highbush blueberries (interspecific hybrids containing mostly Vaccinium corymbosum L.) continue to gain a significant share of the production acreage of commercial blueberries in Georgia. A major reason for the interest in the species has

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Jessica Scalzo

. 37°48′ S, long. 175°17′ E) from a population of seedlings derived from crossing the blueberry cultivars Maru (New Zealand Plant Cultivar Rights Grant #843) and Briteblue (not patented). The new cultivar was created during the course of a planned plant-breeding