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Anik L. Dhanaraj*, Janet P. Slovin, and Lisa J. Rowland

To gain a better understanding of changes in gene expression associated with cold stress in the woody perennial blueberry (Vaccinium spp.), a genomics approach based on the analysis of expressed sequence tags (ESTs) was undertaken. Two cDNA libraries were constructed using RNA from cold acclimated (mid winter conditions when the plants are cold stressed) and non-acclimated (before they received any chilling) floral buds of the blueberry cultivar Bluecrop. About 600 5'-end ESTs were generated from each of the libraries. Putative functions were assigned to 57% of the cDNAs that yielded high quality sequences based on homology to other genes/ESTs from Genbank, and these were classified into 14 functional categories. From a contig analysis, which clustered sequences derived from the same or very similar genes, 430 and 483 unique transcripts were identified from the cold acclimated and non-acclimated libraries, respectively. Of the total unique transcripts, only 4.3% were shared between the libraries, suggesting marked differences in the genes expressed under the two conditions. The most highly abundant cDNAs that were picked many more times from one library than from the other were identified as representing potentially differentially expressed transcripts. Northern analyses were performed to examine expression of eight selected transcripts and seven of these were confirmed to be preferentially expressed under either cold acclimating or non-acclimating conditions. Only one of the seven transcripts, encoding a dehydrin, had been found previously to be up-regulated during cold stress of blueberry. This study demonstrates that analysis of ESTs is an effective strategy to identify candidate cold-responsive transcripts in blueberry.

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

.K. Brewster, V. Vorsa, N. Polashock, J. 2001 Resistance of diploid Vaccinium spp. to the fruit rot stage of mummy berry disease Plant Dis. 85 27 30

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John R. Clark, David Creech, Max E. Austin, M.E. “Butch” Ferree, Paul Lyrene, Mike Mainland, Don Makus, Liz Neuendorff, Kim Patten, and James M. Spiers

Highbush (Vaccinium corymbosum 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. Rabbiteye blueberries appear to have different foliar levels, and may require species-specific standards for nutritional monitoring of plantings.

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James M. Spiers

A greenhouse study was conducted to evaluate the influence of substrate temperatures (16, 27, and 38C) on root and shoot growth of six blueberry (Vaccinium spp.) clones (three clones each of two types). Between types, southern highbush (primarily V. corymbosum L.) produced more roots and total growth than rabbiteye (V. ashei Reade). Comparing clones, `Gulfcoast' (southern highbush) was the most vigorous and `Tifblue' (rabbiteye) the least vigorous. Each clone had a negative linear response to substrate temperatures in all growth characteristics. Root and shoot growth was best at 16C. This study indicates that both rabbiteye and southern highbush blueberries would respond favorably to cultural practices that lower soil temperatures during the summer growing season.

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Jim Hruskoci and Paul E. Read

In an effort to increase somaclonal variation in blueberry, a protocol was developed to regenerate viable shoots from internode segments. The explant consisted of the last-formed, fully developed internode taken from 3 different genotypes of Vaccinium grown in vitro. Explants were cultured 6 weeks on Zimmerman's Z-2 medium supplemented with 2iP, zeatin, thidiazuron, kinetin, or BA at concentrations of 5, 25, 50, and 100 uM. Explant response to the treatments varied and included: no response, callus growth only, callus growth and subsequent shoot formation originating from the callus mass, and adventitious shoot formation directly from the internode segment without an intervening callus. Greatest shoot regeneration (20-25 shoots/explant) was obtained on medium supplemented with zeatin at 5, 25, and 50 uM, however treatment response was not consistant across all genotypes. Regenerated shoots could be readily sub-cultured, rooted in soil mix and will be evaluated for somaclonal variation.

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James J. Polashock and Matthew Kramer

Stem diseases of blueberry (Vaccinium spp.) can cause significant crop loss as well as loss of entire bushes. Stem diseases are also more difficult to control with fungicides than foliar or fruit diseases. A screening program was initiated to test blueberry cultivars for resistance to two pathogenic fungi: botryosphaeria stem blight and phomopsis twig blight. An attached stem assay was developed to compare the host response with both fungi. The relative resistance of 50 blueberry cultivars was assessed using stem lesion lengths, analyzed on a log scale, taken at 4 weeks postinoculation. For Botryosphaeria stem blight, mean lesion length ranged from about 10 mm in resistant cultivars to about 140 mm in susceptible cultivars. The half-high cultivars Northsky, Northblue, and Chippewa, and the lowbush cultivar Putte were among the most resistant. Phomopsis twig blight lesions ranged in mean length from about 18 to 98 mm. Similar to results for Botryosphaeria stem blight, resistance was limited to half-high (`Northsky' and `Chippewa') and lowbush (`Blomidon', `Chignecto', and `Cumberland') cultivars. Individual cultivars resistant to one pathogen were not necessarily resistant to the other; although, overall, the resistances were correlated. Approximate 95% confidence intervals were established for all cultivars to predict mean performance across years. The cultivars tested varied in resistance, but the largest single factor affecting lesion length was the fungal isolate used for inoculations. These data enable us to identify cultivars resistant to both diseases that can be used for planting in problem areas, as well as selection of parental material for breeding cultivars with improved resistance.

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Stephen J. Stringer, Arlen D. Draper, James M. Spiers, Donna A. Marshall, and Barbara J. Smith

Southern highbush blueberries result from hybridizations among the northern highbush blueberry ( Vaccinium corymbosum L.) and other Vaccinium spp. possessing southern U.S. adaptation attributes. Southern highbush blueberry cultivars provide

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Amnon Levi, Elizabeth Ogden, and Lisa J. Rowland

Efforts are underway to develop genetic linkage maps for two interspecific blueberry populations (Vaccinium darrowi × V. elliottii and V. caesariense-derived populations). To date, 72 RAPD markers have been mapped, and another 200 markers have been identified as suitable for mapping in the V. darrowi × V. elliottii-derived population. Inheritance of 40 RAPD markers has been followed, and additional 40 RAPD markers have been identified as suitable for mapping in the V. darrowi × V. caesariense population. These two populations are comprised of individual plants that should have a wide range of chilling requirements. At a later date, plants will be classified according to their chilling requirements to identify RAPD markers that cosegregate with chilling requirements. Presently, a bulked-segregant analysis is being performed on a tetraploid breeding population (primarily V. corymbosum) to identify RAPD markers linked to chilling requirement genes.

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Anish Malladi, Tripti Vashisth, and Scott NeSmith

Blueberry ( Vaccinium spp.) production has increased greatly over the last decade, especially in the southeastern United States. It is currently valued at over $780 million in the United States [ U.S. Department of Agriculture (USDA), 2012

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Anish Malladi, Tripti Vashisth, and Lisa Klima Johnson

Blueberry ( Vaccinium spp.) is rapidly emerging as a major fruit crop in the United States with over 72,000 acres under cultivation and a crop valued at over $780 million U.S. in 2011 [ U.S. Department of Agriculture (USDA), 2012] . Harvesting is a