\u3cem\u3eVaccinium corymbodendron\u3c/em\u3e Dunal as a bridge between taxonomic sections and ploidies in \u3cem\u3eVaccinium\u3c/em\u3e: A work in progress

The species V. corymbodendron of section Pyxothamnus has shown value as a potential bridge between taxonomic sections and ploidies in Vaccinium when involved as either a first generation or second generation parent. Tetraploid V. corymbodendron has hybridized successfully with 2x and 4x section Cyanococcus species and with 2x section Vitis-idaea. Hybridizations with other sections are currently being tested. Second generation allotetraploid V. corymbodendron - V. vitis-idaea hybrids have hybridized successfully with 4x section Oxycoccus (cranberry), 4x section Cyanococcus (blueberry), and 2x section Vitis-idaea (lingonberry). It appears that these allotetraploid hybrids may allow gene movement among these diverse sections at the 4x level. Further test-crosses are being made to evaluate the range of crossability of 4x V. corymbodendron and the V. corymbodendron allotetraploids with other taxonomic sections of Ericaceae

Characterization and Analysis of Anthocyanin-Related Genes in Wild-Type Blueberry and the Pink-Fruited Mutant Cultivar ‘Pink Lemonade’: New Insights into Anthocyanin Biosynthesis

Blueberries are one of the richest sources of antioxidants, such as anthocyanins, among fruits and vegetables. Anthocyanin mutants, like the pink-fruited cultivar ‘Pink Lemonade’, are valuable resources for investigating anthocyanin biosynthesis in blueberries. In this study, we examined expression of flavonoid pathway genes during fruit development in wild-type, blue-fruited blueberries using quantitative real-time PCR. Expression was also compared between wild-type and the pink-fruited ‘Pink Lemonade’. This revealed significantly lower expression in ‘Pink Lemonade’ than in wild-type of nearly all the structural genes examined suggesting that a transcriptional regulator of the pathway was affected. Hence, we compared expression of three known regulatory genes and found that the gene encoding the transcription factor MYB1 was expressed at a significantly lower level in ‘Pink Lemonade’ than in the wild-type. To validate the capacity of this MYB1 to regulate the transcription of anthocyanin genes in blueberries, a transient expression assay was conducted. Results indicated MYB1 overexpression enhanced anthocyanin production. Comparative sequence analysis between wild-type and mutant MYB1 variants found differences in highly conserved features suggesting a mechanistic explanation for the mutant phenotype. Collectively, the results presented here contribute to a better understanding of mechanisms regulating anthocyanin biosynthesis in Vaccinium

RNA-seq combined with a bulked-segregant analysis identifies candidate genes for the waxy coating on blueberry fruit

The most significant difference between blueberries with a light blue fruit color and black fruit color is the visible layer of an epicuticular waxy coating. This layer functions in disease defense and prevention of water loss. In this study, we constructed a northern-adapted rabbiteye hybrid breeding population, ‘Nocturne’ x T 300, which segregated for fruit color (light blue versus black). We screened this population and selected plants of each extreme phenotype, waxy- coated plants with light blue colored fruit versus non-waxy plants with black colored fruit, then isolated RNA from fruit tissue of each bulk, respectively. We sequenced the transcriptome of each bulk using RNA-seq, which resulted in a total of 167,093,354 reads for both libraries combined. We de novo assembled this data set into 171,678 contigs and used the assembled transcriptome as a reference for differential expression analysis using EdgeR. A total of 515 differentially expressed genes were identified with at least a four-fold difference in expression, and efforts were made to functionally annotate them using publicly available databases. From these, one excellent candidate ‘waxy’ gene has emerged, which we are investigating further

Genotype-specific effects of ericoid mycorrhizae on floral traits and reproduction in Vaccinium corymbosum

American Journal of Botany is published by Wiley Periodicals, Inc. on behalf of the Botanical Society of America. Premise: Most plants interact with mycorrhizal fungi and animal pollinators simultaneously. Yet, whether mycorrhizae affect traits important to pollination remains poorly understood and may depend on the match between host and fungal genotypes. Here, we examined how ericoid mycorrhizal fungi affected flowering phenology, floral traits, and reproductive success, among eight genotypes of highbush blueberry, Vaccinium corymbosum (Ericaceae). We asked three overarching questions: (1) Do genotypes differ in response to inoculation? (2) How does inoculation affect floral and flowering traits? (3) Are inoculated plants more attractive to pollinators and less pollen limited than non-inoculated plants of the same genotype?. Methods: To examine these questions, we experimentally inoculated plants with ericoid mycorrhizal fungi, grew the plants in the field, and measured flowering and floral traits over 2 years. In year 2, we conducted a hand-pollination experiment to test whether plants differed in pollen limitation. Results: Inoculated plants had significantly higher levels of colonization for some genotypes, and there were significant floral trait changes in inoculated plants for some genotypes as well. On average, inoculated plants produced significantly larger floral displays, more fruits per inflorescence, and heavier fruits with lower sugar content, than non-inoculated, control plants. Hand pollination enhanced the production of fruits, and fruit mass, for non-inoculated plants but not for those that were inoculated. Conclusions: Our results demonstrate that inoculation with ericoid mycorrhizal fungi enhanced flowering and altered investment in reproduction in genotype-specific ways. These findings underscore the importance of examining belowground symbionts and genotype-specific responses in their hosts to fully understand the drivers of aboveground interactions

Hybridization between wild and cultivated potato species in the Peruvian Andes and biosafety implications for deployment of GM potatoes

The nature and extent of past and current hybridization between cultivated potato and wild relatives in nature is of interest to crop evolutionists, taxonomists, breeders and recently to molecular biologists because of the possibilities of inverse gene flow in the deployment of genetically-modified (GM) crops. This research proves that natural hybridization occurs in areas of potato diversity in the Andes, the possibilities for survival of these new hybrids, and shows a possible way forward in case of GM potatoes should prove advantageous in such areas

There and back again: historical perspective and future directions for Vaccinium breeding and research studies

The genus Vaccinium L. (Ericaceae) contains a wide diversity of culturally and economically important berry crop species. Consumer demand and scientific research in blueberry (Vaccinium spp.) and cranberry (Vaccinium macrocarpon) have increased worldwide over the crops' relatively short domestication history (~100 years). Other species, including bilberry (Vaccinium myrtillus), lingonberry (Vaccinium vitis-idaea), and ohelo berry (Vaccinium reticulatum) are largely still harvested from the wild but with crop improvement efforts underway. Here, we present a review article on these Vaccinium berry crops on topics that span taxonomy to genetics and genomics to breeding. We highlight the accomplishments made thus far for each of these crops, along their journey from the wild, and propose research areas and questions that will require investments by the community over the coming decades to guide future crop improvement efforts. New tools and resources are needed to underpin the development of superior cultivars that are not only more resilient to various environmental stresses and higher yielding, but also produce fruit that continue to meet a variety of consumer preferences, including fruit quality and health related trait

Chemical constituents of the leaves of rabbiteye blueberry (Vaccinium ashei) and characterisation of polymeric proanthocyanidins containing phenylpropanoid units and A-type linkages

Chemical constituents of the leaves of rabbiteye blueberry (Vaccinium ashei READE) were investigated in detail. The major phenolic components were caffeoyl quinic acids, flavonol glycosides, flavan-3-ols and proanthocyanidins. Catechins and proanthocyanidins having additional phenylpropanoid units, such as cinchonains, kandelins and mururins, characterised the polyphenols of this plant. Among them, vaccinin A, an isomer of mururin A, was found to be a new compound, and the structure was characterised by spectroscopic methods. The most abundant polyphenols (11.3% of freeze-dried leaves) were oligomeric proanthocyanidins. Thiol degradation with mercaptoethanol indicated that the polymer was constituted of (+)-catechin and (-)-epicatechin as the terminal units and (-)-epicatechin, procyanidin A-2, and cinchonains Ia and Ib as the extension units. Mass spectral analysis suggested the presence of at least dodecamers with A-type linkages and phenylpropanoid moieties

Cluster illumination differentially affects growth of fruits along their ontogeny in highbush blueberry (Vaccinium corymbosum L.).

Shading highbush blueberry plants generally leads to a delayed fruit development. Experiments have been performed to study the effects of light on fruit growth independently from the rest of the canopy. Clusters were shaded during different fruit growth periods. The equatorial diameter of the fruits as a function of days after full bloom followed a double-sigmoidal growth pattern, being fitted using a Gompertz II nonlinear mixed model, and absolute growth rates were obtained from each fitted model. Both whole-cycle shaded and second-stage shaded fruits showed a delayed peak in absolute growth curves with respect to both first-stage shaded and whole-cycle unshaded controls. Our results suggest that deficiency of light during the last stage of highbush blueberry fruits may lead to a substantial delay (of about 10–16 days) in harvest as compared with well-illuminated fruits. In order to estimate the contribution of intrinsic fruit photosynthesis to its own growth at different stages, clusters were subjected to girdling on their peduncles at different times. Girdling just before the second-stage resulted in fruits gaining between 35 and 40% of dry weight in comparison with the controls. This suggests that fruit photosynthesis may play a relevant role in fruit growth during the second sigmoidal stage, which in turn may contribute to explain the delayed growth observed in shaded fruits