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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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Gregory A. Lang and E. James Parrie

Pollen from six southern highbush blueberry cultivars derived from Vaccinium corymbosum L. and one or more other species (V. darrowi Camp, V. ashei Reade, and V. angustifolium Aiton) was incubated on nutrient agar to determine tetrad viability, pollen tube growth rates, and incidence of multiple pollen tube germinations. `Avonblue' pollen had a significantly lower tetrad germination percentage than `Georgiagem', `Flordablue', `Sharpblue', `Gulfcoast', or `O'Neal', all of which had >90% viable tetrads. The in vitro growth rate of `O'Neal' pollen tubes was significantly higher than the growth rates of `Sharpblue' and `Georgiagem pollen tubes. Of those tetrads that were viable, more than two pollen tubes germinated from 83% and 91% of the `Gulfcoast' and `Sharpblue' tetrads, respectively, while only 11% of the `Flordablue' tetrads produced more than two pollen tubes. The total number of pollen tubes germinated per 100 tetrads ranged from 157 (`Flordablue') to 324 (`Sharpblue'), resulting in actual pollen grain viabilities ranging from 39% to 81%. Genetic differences in pollen vigor, as indicated by pollen viability, pollen tube growth rates, and multiple pollen tube germinations, may influence blueberry growers' success in optimizing the beneficial effects of cross-pollination on fruit development.

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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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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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Christopher S. Imler, Camila I. Arzola, and Gerardo H. Nunez

, such as blueberries ( Vaccinium spp. section cyanococcus). Development of cultivars and practices that reduce dependence on these inputs requires a better understanding of the processes that affect rhizosphere pH. Some herbaceous and woody plants can

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Yifei Wang, Stephanie K. Fong, Ajay P. Singh, Nicholi Vorsa, and Jennifer Johnson-Cicalese

.L. Ehlenfeldt, M.K. Vander Kloet, S.P. 2001 Interspecific variation in anthocyanins, phenolics, and antioxidant capacity among genotypes of highbush and lowbush blueberries ( Vaccinium section cyanococcus spp. ) J. Agr. Food Chem. 49 4761 4767 Krewer, G. NeSmith

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David R. Bryla, Robert G. Linderman, and Wei Q. Yang

Phytophthora cinnamomi Rand. ( Caruso and Ramsdell, 1995 ), a widespread soil pathogen with a large host range first reported in northern highbush blueberry ( Vaccinium corymbosum L.) in 1961 ( Raniere, 1961 ). Since then, P. cinnamomi has been documented

Open access

Ebrahiem M. Babiker, Stephen J. Stringer, Hamidou F. Sakhanokho, Barbara J. Smith, and James J. Polashock

Vaccinium species in crosses to incorporate genes for adaptation; however, little is known about Neofusicoccum species identification and the responses of native Vaccinium species to infection. Morphological differentiation between different species of

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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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Jeffrey G. Williamson and Jonathan H. Crane

( Hylocereus spp. and hybrids), sapodilla, and sugar apple ( Annona squamosa ). The average size farm is 27 acres, but the most common size orchard (greater than 57%) is between 1 and 9 acres ( Degner et al., 2002 ; Migliaccio et al., 2006 ; USDA, 2009