Transcriptome analysis and identification of genes associated with floral transition and fruit development in rabbiteye blueberry (Vaccinium ashei)

Flowering and fruit set are important traits affecting fruit quality and yield in rabbiteye blueberry (Vaccinium ashei). Intense efforts have been made to elucidate the influence of vernalization and phytohormones on flowering, but the molecular mechanisms of flowering and fruit set remain unclear. To unravel these mechanisms, we performed transcriptome analysis to explore blueberry transcripts from flowering to early fruit stage. We divided flowering and fruit set into flower bud (S2), initial flower (S3), bloom flower (S4), pad fruit (S5), and cup fruit (S6) based on phenotype and identified 1,344, 69, 658, and 189 unique differentially expressed genes (DEGs) in comparisons of S3/S2, S4/S3, S5/S4, and S6/S5, respectively. There were obviously more DEGs in S3/S2 and S5/S4 than in S4/S3, and S6/S5, suggesting that S3/S2 and S5/S4 represent major transitions from buds to fruit in blueberry. GO and KEGG enrichment analysis indicated these DEGs were mostly enriched in phytohormone biosynthesis and signaling, transporter proteins, photosynthesis, anthocyanins biosynthesis, disease resistance protein and transcription factor categories, in addition, transcript levels of phytohormones and transporters changed greatly throughout the flowering and fruit set process. Gibberellic acid and jasmonic acid mainly acted on the early stage of flowering development like expression of the florigen gene FT, while the expression of auxin response factor genes increased almost throughout the process from bud to fruit development. Transporter proteins were mainly associated with minerals during the early flowering development stage and sugars during the early fruit stage. At the early fruit stage, anthocyanins started to accumulate, and the fruit was susceptible to diseases such as fungal infection. Expression of the transcription factor MYB86 was up-regulated during initial fruit development, which may promote anthocyanin accumulation. These results will aid future studies exploring the molecular mechanism underlying flowering and fruit set of rabbiteye blueberry.

Complementary Contribution of Wild Bumblebees and Managed Honeybee to the Pollination Niche of an Introduced Blueberry Crop

The entomophilous pollination niche (abundance, phenotypic traits, foraging behaviours and environmental tolerances of insect pollinators) helps to understand and better manage crop pollination. We apply this niche approach to assess how an entomophilous crop (blueberry, Vaccinium ashei) can be expanded into new territories (i.e., northern Spain) far from their original area of domestication (North America). Insect visits to blueberry flowers were monitored in a plantation on 12 different days, at 8 different times during day and covering various weather conditions. Abundance, visitation rate, pollen gathering behaviour, and frequency of inter-plant and inter-row movements were recorded. The pollinator assemblage was basically composed of one managed honeybee species (50.8% of visits) and three native bumblebee species (48.3%). There was a marked pattern of seasonal segregation throughout bloom, with bumblebees dominating the early bloom and honeybee the late bloom. Pollinators also segregated along gradients of daily temperature and relative humidity. Finally, the two pollinator types differed in foraging behaviour, with bumblebees having a visitation rate double that of honeybee, collecting pollen more frequently and changing plant and row more frequently. The spatio-temporal and functional complementarity between honeybee and bumblebees suggested here encourages the consideration of an integrated crop pollination strategy for blueberries, based on the concurrence of both wild and managed bees.

Transcriptomic analysis reveals anthocyanin biosynthesis regulation in blueberry (Vaccinium ashei) fruit

Blueberry (Vaccinium ashei) is a popular fruit due to its high anthocyanin content. This study aimed to analyze the transcriptome profile of V. ashei cv. ‘Brightwell’ fruits at different stages of development. A total of 314.26 GB of clean data were obtained and de novo assembled into 254,196 unigenes. In comparisons between the early and late stages of fruit ripening, 27 genes (including PAL, CHS, F3H, F3ʹH, F3ʹ5ʹH, LDOX, etc.) were found to cover the main steps in the anthocyanin biosynthesis pathway. Most of these genes were highly expressed in the late stage of fruit development, suggesting that anthocyanin mainly accumulate in the late stage. During the late stage of fruit development, most structural and regulatory genes such as F3ʹ5ʹH and F3ʹH, which are involved in the anthocyanin biosynthetic pathway, were upregulated, causing the fruit to turn blue. Decreased expression of a large number of chloroplast-related genes during the fruit ripening period could explain why the green fruit color fades over time. Additionally, abscisic acid and ethylene may play positive roles in promoting fruit ripening and anthocyanin accumulation. This research reveals the transcriptomic characteristics of immature and mature fruits and enhances our understanding of the molecular mechanisms of anthocyanin biosynthesis and accumulation in blueberry fruit.

Atividade antioxidante de pequenas frutas produzidas no Estado do Rio Grande do Sul, Brasil

A busca por pequenos frutos, por consumidores, tem aumentado nos ultimos tempos devido as grandes pesquisas sobre bioativos, que trazem benefícios associados à manutenção e bem-estar da saúde. Com isso, as agroindústrias também têm focado na expansão do mercado consumidor de polpas de frutas. Assim sendo, as culturas de amora-preta e mirtilo ganham espaço dentre outras espécies, das pequenas frutas consumidas no Brasil, despertam a atenção de consumidores, processadores de frutas, agentes comercializadores e, por consequência, por produtores em escala familiar, médio e de grande porte. O objetivo deste estudo foi avaliar a atividade antioxidante da polpa in natura, da polpa diluída e da polpa liofilizada de amora-preta cv. Tupy e de mirtilo cv. Powderblue. Foram utilizados frutos de amora-preta (Rubus fruticosus) da cultivar cv.Tupy, e mirtilos (Vaccinium ashei Reade) da cv. Powderblue, ambos cultivados na cidade de Morro Redondo-RS. Os frutos previamente congelados (-18°C) foram mantidos à temperatura ambiente até o descongelamento, e em seguida foram triturados em liquidificador e peneirados para obtenção da polpa, que foram diluidas com água mineral nas proporções de 50% e 75% p/v (polpa: água). As frutas também foram armazendas e retiradas do ultrafreezer (-80°C) e imediatamente liofilizadas, após foram armazenadas em embalagens de polietileno sob congelamento (-20±2°C) até o momento das análises. A atividade antioxidante foi determinada seguindo o método descrito por Brand-Willians. Portanto, verificou-se que a polpa -in natura de mirtilo cv. Powderblue apresenta maior capacidade antioxidante que a amora- preta cv. Tupy.

Osmia lignaria (Hymenoptera: Megachilidae) produce larger and heavier blueberries than honey bees (Hymenoptera: Apidae)

Fruit set, berry size, and berry weight were assessed for pollination by the solitary bee Osmia lignaria (Say) in caged rabbiteye blueberries (Vaccinium ashei Reade, Ericales : Ericaceae), and compared to that of uncaged rabbiteye blueberries which were pollinated largely by honey bees (Apis mellifera L). O. linaria produced berries that were 1.6mm larger in diameter and 0.45g heavier than uncaged blueberries. Fruit set was 40% higher in uncaged blueberries. This suggests that Osmia bees can produce larger and heavier berry fruit, but O. lignaria may be less efficient at blueberry pollination as compared to A. mellifera under field cage conditions.