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Title: Inheritance Patterns of Parthenocarpic Fruit Development in Highbush Blueberry (Vaccinium corymbosum L.)

item Ehlenfeldt, Mark

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2007
Publication Date: 7/1/2007
Citation: Vorsa, N., Ehlenfeldt, M.K. 2007. Inheritance Patterns of Parthenocarpic Fruit Development in Highbush Blueberry (Vaccinium corymbosum L.). HortScience. 42:1127-1130.

Interpretive Summary: Blueberry plants typically require pollination by insects such as bees in order to produce fruit. However in some years pollination is poor, either due to poor health of the insects or poor weather. Therefore parthenocarpy, the production of fruit without pollination or seed development, is a desirable trait because it holds the possibility of reducing these pollination problems and therefore producing more predictable harvest year after year. A highbush blueberry plant was identified that appeared to set fruit whether pollinated or not pollinated (ie parthenocarpy). This plant was used as a parent in a series of crosses to other blueberry selections to generate a series of blueberry ‘families’. These blueberry ‘families’ were evaluated under field conditions to study inheritance. In general, three categories of offspring were observed: normal fruit with seeds, fruit with few or very small seed, and seedless fruit. Evaluations of inheritance patterns found that seedlessness generally behaved as a recessive character, like blue eyes in people, but the environment also had a large role on the production of seedless fruit. This information will be valuable to all blueberry breeding programs interested in developing varieties with consistent yield regardless of the availability of pollinating insects or the weather during the flowering season.

Technical Abstract: F2 populations segregating for the trait of parthenocarpic fruit production, comprised of 41 families and >3000 individuals, were evaluated under field conditions. Among these populations, approximately 280 parthenocarpic individuals were identified. In general, three categories of segregants were observed: normal types, small/low seeded types, and parthenocarpic types. Evaluations of inheritance patterns found the trait generally behaved as a recessive, but did not fit well to tetrasomic recessive or dosage-effect segregation models. Lack of fit was attributed to environmental effects on expression of parthenocarpy. Further evaluations are underway with small/low seeded types with the expectation that offspring of these plants may express the trait at higher frequencies. The lesser vigor (in many cases) of parthenocarpic clones suggests that this germplasm will be most useful, initially, in improving fruit quality in the intermediate small/low seeded types which have better fruit set, and reduced seed development.