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Title: Evidence of functional gender polymorphisms in a population of the hermaphroditic lowbush blueberry (Vaccinium angustifolium)

item Bell, Daniel
item DRUMMOND, FRANK - University Of Maine
item Rowland, Lisa

Submitted to: Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2011
Publication Date: 5/1/2012
Citation: Bell, D.J., Drummond, F.A., Rowland, L.J. 2012. Evidence of functional gender polymorphisms in a population of the hermaphroditic lowbush blueberry (Vaccinium angustifolium). Botany. 90:393-399.

Interpretive Summary: Lowbush blueberry production, which makes up about 1/3 of the total blueberry production in the U.S., is from managed wild fields in Maine. Individual plants of wild lowbush blueberry are quite variable in terms of yield and we are investigating possible causes of these yield differences. It has been suggested that lowbush blueberry may be in the process of evolving into having separate sexes, plants that function as males and plants that function as females. This could explain why some plants (the males) produce little or no fruit. We investigated this possibility by examining 56 different lowbush blueberry plants in a field in Maine for male traits and female traits. We found no evidence for plants specializing into separate males and females. This information will be useful to other scientists interested in improving yields in lowbush blueberry.

Technical Abstract: Lowbush blueberry is a wild, but cultivated for profit, agricultural system grown primarily along the northeastern regions of North America. Adjacent plants, grown under optimized growth conditions, can show dramatic yield variation. Previously, both self-fertility rates and combining abilities have been concretely shown to be involved. However, in addition, it has been suggested that a functional gender specialization may be occurring in this hermaphroditic species in which some clones effectively function as bearers (high ovule production but little or non-viable pollen) or as pollen donors (low ovule number with high quantities of viable pollen). This study examines the possibility of this occurring in 56 randomly chosen clones from the Blueberry Research Farm in Maine. For each of these clones, the mean number of ovules per flower (OPF), mean tetrads per flower (TPF), proportion viable pollen (PVP) and mean viable microspores per flower (VMPF) was counted. Non-parametric correlation analysis revealed no significant correlations between any combinations of these four fertility parameters. Thus, no evidence was found of a functional gender specialization in this hermaphroditic species or that such could be an additional factor accounting for yield variation. Results are contextualized in the extant theory of the selection pressures presumably required to elicit a functional gender specialization over time and in terms of key differences between the studies, especially our choice to count ovules rather than mature seed as the female fertility component.