Transport of Cross-pollen by Bumblebees in a Rabbiteye Blueberry Planting

Abstract

<jats:p>Blueberries are bee-pollinated species that benefit from cross-pollination. Cross-pollination is particularly critical for optimum fruit set of rabbiteye blueberries (<jats:italic>Vaccinium ashei</jats:italic> Reade) because of their limited degree of self-fertility. In order to determine if the failure to set adequate commercial fruit loads is due to a lack of cross-pollination, research was needed to establish how much out-crossing rabbiteye blueberry pollinators actually do. A novel method was developed to identify pollen grains on the bodies of bumblebees by cultivar. The technique discriminates between two cultivars, based on differences in pollen diameter. Bumblebees were collected in a plot composed of blueberry plants of the cultivars Brightwell and Climax since these cultivars produce pollen of different size. Pollen loads of bumblebees contained low proportions of cross-pollen regardless of the cultivar they were visiting. Data suggest that inadequate levels of cross-pollination play a major role in low fruit set problems of rabbiteye blueberry. The composition of bees' pollen load changed with the phenology of the crop. The greatest likelihood for cross-pollination occurred around the time of maximum bloom overlap. Bumblebees foraging on `Brightwell' flowers carried more total blueberry pollen and a higher proportion of self-pollen than those visiting `Climax'. This may be due to differences in pollen release between flowers of these two cultivars.</jats:p>

Pollination of ‘Hortblue Petite’ Blueberry: Evidence of Metaxenia in a New Ornamental Home-garden Cultivar

“…With open pollination, bees deposit pollen from a variety of sources provided those sources are available, some of which are more compatible than others with the maternal tissues (Vander Kloet, 1991). Results from the present study are consistent with this observation and add support to the suggestion of Brevis and NeSmith (2005) that source of pollen deposited plays an important role in determining fruit set in blueberries. Although cross-pollination was better, 'Hortblue Petite' appears to have a high degree of self-fertility and can exhibit adequate fruit set under field conditions without crosspollination.…”

“…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).…”

Effects of Timing of CPPU Applications on Rabbiteye Blueberries

“…Poor fruit set and small berry size can limit production of rabbiteye blueberries (Vaccinium ashei Reade) grown in the southeastern United States (Scherm et al, 2001). Some factors that affect fruit set include pollinator population during bloom, crosspollinating activity and pollen transfer during bloom, and subfreezing temperatures during, or after, bloom, which damage ovules and ovaries thereby inhibiting seed and fruit development (Brevis and NeSmith, 2005;Brevis et al, 2006aBrevis et al, , 2006b. Much research over the past decade has focused on use of gibberellic acid (GA 3 ) to overcome some of the fruit set problems in blueberries grown in the lower southeastern United States NeSmith and Krewer, 1992, 1997a, 1997b.…”