Cross-pollination Improves Fruit Quantity and Quality Across Northern and Southern Highbush Blueberry Cultivars

Overview & Synopsis

Cultivated blueberries ( Vaccinium spp.) are partially self-sterile because of early-acting inbreeding depression and, as such, they may set fruit with self-pollination, but with a lower quantity and quality than that with cross-pollination. A lack of recent research of the pollination requirements of modern cultivars as well as shifting management and harvesting priorities have contributed to the increasing prevalence of single-cultivar blocks. However, cross-pollen limitation may be a significant factor that contributes to reduced pollination levels and low yields in these contexts. In this study, we applied hand-pollination treatments in a greenhouse and compared the effects of cross-pollination and self-pollination on numerous fruit responses related to both quantity and quality of 20 cultivars of both northern highbush (NHB) ( Vaccinium corymbosum ) blueberry and southern highbush (SHB) ( V. corymbosum hybrids) blueberry. Cross-pollination improved the resulting fruit weight per pollinated flower for all SHB cultivars and 7 of 10 NHB cultivars. Increases ranged from 18% to 380% because of greater fruit set and/or weight of the set berries. Cross-pollination also reduced times to ripen for 9 of 10 SHB cultivars and 7 of 10 NHB cultivars. Cross-pollination reduced time to ripen by 3 to 27 days and increased seed set in all but one NHB cultivar. Effects on fruit quality were more variable and included fruit firmness and sugar:acid ratios, but there was some evidence of increased fruit firmness under cross-pollination in six NHB cultivars. Finally, effects were generally consistent across three to eight cross-pollen donors tested for each recipient cultivar, with a few exceptions. These results show that cross-pollination has significant and positive impacts on yields and ripening time of cultivated blueberry; however, the magnitude of the effect varies across cultivars. Furthermore, the consistency of effects across tested cross-pollen donors suggests that the selection of cultivars to plant together for optimal pollination outcomes should be based on management and overlapping phenology.