Many fruit trees require cross-pollination to reach their full yield potential. In highbush blueberries (Vaccinium corymbosum L. and its hybrids), optimal pollination by genotype combination results in higher fruit set, larger berries, and earlier ripening (Bieniasz, 2007; Ehlenfeldt, 2001). Pollination effects have also been recorded in rabbiteye blueberries (V. virgatum syn. ashei Reade), particularly for fruit set (Brevis and NeSmith, 2005; El-Agamy et al., 1981; Payne et al., 1989). Both highbush and rabbiteye blueberries are available in retail garden centers for use in home gardens as are a number of different Vaccinium species (Trehane, 2004). Different fruiting characteristics between blueberry types, including maturation time, berry size, and yield, allow gardeners the opportunity to mix species and thereby extend the harvest season. Gardeners may also be interested in the visual effects of mass planting with a single type of ornamental blueberry. Whereas the need for cross-pollination between cultivars is widely acknowledged by commercial growers, there is little information available on cultivar compatibility for home gardeners. Thus, when a new blueberry cultivar becomes available to the retail sector, one of the first questions from a home gardener is whether the plant is self-fertile and can be planted as a single specimen.
‘Hortblue Petite’ is a compact, small-statured highbush blueberry cultivar, no more than 1.5 m in height. It was selected from open-pollinated seed of a dwarf tetraploid V. corymbosum in New Zealand's temperate oceanic climate and introduced as an ornamental type to the New Zealand retail sector in 2005 (Scalzo et al., 2009). ‘Hortblue Petite’ has a low chill requirement compared with standard highbush blueberry varieties (e.g., ‘Duke’, ‘Bluecrop’, ‘Elliott’), flowers prolifically in spring, and may have a second or third flowering event during the growing season if favorable conditions exist. The berries are small (less than 1.0 g) and dark blue in color with the main crop in New Zealand harvested in mid- to late December (Scalzo et al., 2009). ‘Hortblue Petite’ fruits prolifically in research plots, where bees are the main pollinator. Pollen is freely available for transfer from many sources including different Vaccinium species. However, there is little information on fruit set or yield of ‘Hortblue Petite’ in home gardens where pollen sources might be limited. It is generally accepted that self-fertility is low in most Vaccinium species (Chavez and Lyrene, 2009; Vander Kloet and Lyrene, 1987). Productivity of ‘Hortblue Petite’ in the home garden might be limited by insufficient pollen sources, particularly if the cultivar exhibits a degree of self-infertility.
This study was undertaken primarily to evaluate self- and cross-fertility of ‘Hortblue Petite’ with a number of other blueberry cultivars and genotypes. The wide variation in fruit size of genotypes used as pollenizers made it possible to explore a secondary aim to investigate effects of pollen source on fruit weight in ‘Hortblue Petite’, thus investigating evidence of metaxenia in blueberry.
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