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K. Haghighi and J.F. Hancock

Restriction fragment analyses of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) were carried out on the principal cytoplasms of northern highbush cultivars and one representative of Vaccinium ashei Reade. Twenty-three restriction enzymes were used to identify variation and clarify mode of organelle inheritance. All species and genotypes displayed identical cpDNA fragment patterns, but high degrees of polymorphism were observed in the mitochondrial genomes. `Bluecrop' and `Jersey' did not appear to have `Rubel' cytoplasm as was previously believed. All hybrids contained maternal-type mtDNA.

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J.R. Ballington, C.M. Mainland, S.D. Duke, A.D. Draper, and G.J. Galletta

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Lisa J. Rowland, Elizabeth L. Ogden, Mark K. Ehlenfeldt, and Rajeev Arora

first three DOD for both genotypes. During this time interval, the V. ashei (southern species) genotype ‘Tifblue’ lost significantly more of its initial BCH, 11.2 °C or ≈51%, than did the V . corymbosum genotype ‘Bluecrop’, which lost ≈8.6 °C or ≈33

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Mark K. Ehlenfeldt, Lisa J. Rowland, Elizabeth L. Ogden, and Bryan T. Vinyard

deacclimation indicated that V. constablaei was particularly late to deacclimate, and ‘Little Giant’, a 50:50 hybrid of V. constablaei and V. ashei , was nearly as late to deacclimate as pure V. constablaei . Thus, V. constablaei was posited as

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

Data from a four-parent diallel, involving one highbush (Vaccinium corymbosum L.) clone and three interspecific hybrids grown on mineral soil unamended with organic matter, were analyzed to determine combining ability effects for six traits: plant size, berry size, the number of days between flowering and fruiting (# DBF&F), the ratio of total fruit weight to canopy volume (TFW: CYV), days to fruit ripe, and yield. General combining ability effects were significant for all characters tested, except yield and berry size in 1984. Specific combining ability effects were significant for plant size in 1983, #DBF&F in 1984, TFW: CYV in 1984, and berry size in 1985. Vigorous and productive highbush cultivars can be developed for mineral soils by using the interspecific clones from this study and their selected recombinant to combine the genes for plant vigor with the high-quality fruit traits of highbush cultivars.

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James N. Moore

The blueberry cultivar situation in North America is undergoing rapid change. Attempts to grow blueberries in non-traditional areas, and increased biotic and abiotic challenges in traditional production areas, are fueling the search for superior, adapted cultivars. This survey of all blueberry-producing states/provinces in the United States and Canada provides the current status and projected trends in blueberry cultivar use in North America. Most (86%) of current hectarage is comprised of 25 northern highbush, 10 rabbiteye, and two southern highbush cultivars. `Bluecrop' is the dominant northern highbush cultivar, with 35% of the highbush area, while `Tifblue' occupies 40% of the rabbiteye area. Some historically important cultivars, such as `Jersey', `Weymouth', and `Woodard' are in decline. New cultivars of all blueberry types are beginning to have a positive impact on the blueberry industry.

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Rogério Ritzinger and Paul M. Lyrene

Several morphological features of Vaccinium ashei Reade, V. constablaei A. Gray, their F1 hybrids, V. simulatum Small, and southern highbush blueberry (V. corymbosum L. hybrids) flowers were compared in Gainesville, Fla. Desirable characteristics that could increase the extent of honeybee pollination, such as a large corolla aperture and a short anther-to-stigma distance, were common in V. constablaei but not in V. ashei. F1 (V. ashei × V. constablaei) hybrids were generally intermediate between the two parents. Thus, it appears that V. constablaei could be used to breed V. ashei cultivars with improved flower morphology. Vaccinium simulatum and V. constablaei flowers were similar in all features. The corollas of southern highbush blueberry flowers were wide and had wide apertures, but the distance between stigma and anther pore was also large.

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James N. Moore

Expansion of blueberry culture in North America has occurred during the past decade and is projected to continue into the next century. Thirty-six U.S. states and six Canadian provinces report some blueberry production. The area planted to blueberries has inreased by 19% in 10 years, with the largest increase (47%) in cultivated types and only 11% in wild blueberries. It is projected that the total area will increase by an additional 14% by the year 2000. New cultivars are proving of value and are affecting the composition of plantings. Greater interest is being given to mechanical harvesting, and new cultural and pest control innovations are being employed to enhance the economics of production. The expansion of blueberry production is being undergirded by expanded programs in problem-solving research.

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Mark Ehlenfeldt and Lisa Rowland

In recent years, the U.S. Department of Agriculture has generated V. ashei and V. constablaei derivatives to provide late-flowering, earlyripening rabbiteye germplasm for the southern U.S.; however, this germplasm has also performed well in New Jersey, and could potentially provide northern-adapted rabbiteye types. When combined, these germplasms complement each other in many respects. Crosses with varying percentages of V. constablaei germplasm ranging from 100% to 0%, in 25% increments, were evaluated for mid-winter cold-hardiness using a detached twig assay. Hybrids with 50% or more V. constablaei germplasm were hardy to –25° C or lower. Further backcrosses to V. ashei resulted in dramatic segregation for hardiness, but still yielded some progeny as hardy as typical northern highbush. Assays of rabbiteye cultivars have been recently completed to enhance the ability to generate cold-hardy hybrids. Recombination and selection have begun to yield hybrids improved for critical commercial characteristics, and further rapid progress is expected.

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Mark K. Ehlenfeldt, Elizabeth L. Ogden, Lisa J. Rowland, and Bryan Vinyard

The midwinter cold hardiness of 25 rabbiteye (V. ashei) blueberry cultivars was assayed across 2 years using a shoot freezing assay. LT50values (i.e. temperature at which 50% of buds are damaged) for the cultivars ranged from –24.9 °C for `Pearl River' (a 50% V. ashei derivative) to –13.7 °C for `Chaucer'. Under New Jersey conditions, numerous cultivars were observed to exhibit dimorphism for dormant floral bud size. Comparisons of bud dimorphism with LT50 values, found dimorphism more common in cultivars with lower floral bud hardiness. LT50 values generally supported empirical observations of winter hardiness, but exceptions suggest that additional factors contribute to observed winter hardiness under field conditions.