Self-fruitfulness of Rutgers’ Advanced Blueberry Breeding Selections

The Rutgers highbush blueberry breeding program is focused on the development of machine-harvestable varieties for the fresh market. New Jersey growers have relied largely on available migrant hand-labor for harvest. Increasing restrictions on management options, e.g., labor availability, increased pesticide re-entry periods, etc., have placed additional burdens on farm sustainability, making machine-harvestable fresh fruit varieties highly desirable. Another required trait in a new variety is self-fruitfulness. In large blocks of a single cultivar, most ova are self-fertilized, resulting in high seed abortion, resulting in reduced fruit set and size. Thus, many if not most highbush blueberry cultivars do not achieve maximum production in large single cultivar plantings, where self-fertilization predominates. Unfortunately, due to the high varietal diversity in typical breeding blocks, virtually all blueberry breeding programs measure fruitfulness in a fairly cross-pollinated environment. Therefore, we are now evaluating the self-fruitfulness of our machine-harvestability selections in controlled greenhouse crosses. This study evaluated 30 progeny (selections), representing 15 crosses, for self-fruitfulness in the greenhouse, as measured by fruit size, ripening period and fruit set. Respective flower clusters were pollinated with either the selection’s own pollen or pollen from ‘Sierra’, ‘Bluecrop’, or unrelated selections. Cross-pollinated flowers typically yielded larger, earlier ripening fruit for most selections. Relative to cross-pollinated clusters, fruit set was reduced, and fruit ripening was delayed by an average of 3 to 4 days and fruit size reduced by an average of 18% in self-pollinated clusters. However, self-fruitfulness varied widely among the 30 selections, with some exhibiting only a small effect, and others exhibiting a severe reduction in size, delayed ripening and reduced fruit set. Variation for self-fruitfulness between progeny of a given cross was also observed; reduction in fruit size with self-pollination ranged from 7 to 59% and ripening was delayed from 2 to 23 days. A second year of data is now being collected on these selections, including seed set counts, an important determinate of fruit size. In conclusion, a number of selections appeared to have comparable fruit set, fruit size and ripening season under self-pollination versus cross-pollinated flowers, making them good candidates for commercial production. However, a few of our selections exhibited severe self-unfruitfulness and would likely be unsuitable for the commercial grower.Paper presented at NABREW Conference, Paper Session II:Breeding and Genetics, on June 25, 2014, Atlantic City, N.J