Blueberry is a crop that has been increasing in importance worldwide (Strik and Yarborough, 2005) with areas expanding in non-traditional subtropical areas (Bañados, 2009). In 2012, there were ≈84,000 ha of cultivated blueberry worldwide with the majority located in the United States and Canada and yield exceeded 399,000 tons (Food and Agriculture Organization of the United Nations, 2014). Flower or inflorescence bud number is the most important component of yield in many crops, including blueberry (Salvo et al., 2011) and is determined by the extent of floral bud initiation and development that occurs in late summer and early fall. The extent and timing of inflorescence bud initiation and development in blueberry may affect bloom time the next spring (Spann et al., 2004), which plays a critical role in yield. Early bloom may be subject to damage by spring freezes with resultant crop losses, whereas late bloom may delay harvest.
There have been few studies examining inflorescence bud differentiation in blueberry. Bell and Burchill (1955) described the formation of individual flowers within the inflorescence bud in lowbush blueberry (V. angustifolium). Gough et al. (1978b) described the development of the inflorescence in field-grown northern highbush blueberry (V. corymbosum) using only floral buds from the fourth node from the shoot apex. Both studies described the histological formation of flowers, but information on the formation of the inflorescence was limited. Tamada (1997) described differentiation of the inflorescence in terminal buds in field-grown highbush and rabbiteye (V. virgatum) blueberry but did not examine differentiation of more proximal buds. Huang et al. (1997) evaluated floral development in SHB, but only after flowers were already present.
Previous assessments of floral development in blueberry are limited and have focused on single inflorescence buds rather than the development and distribution of floral buds in a shoot, even though there are timing differences in development of apical vs. more proximal inflorescence buds (Huang et al., 1997; Lyrene, 1984). Furthermore, the relationship between timing and extent of blueberry inflorescence bud development in the fall and subsequent bloom progression in the spring has not been determined. The objectives of the present study were to: 1) describe the internal development of blueberry inflorescence buds; 2) compare the timing and node location of inflorescence bud initiation in two cultivars of SHB; and 3) determine the relationship between timing and extent of internal inflorescence bud development with the bloom period the next spring in the same two cultivars.
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