Date of Award

5-2009

Level of Access

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Sciences

Advisor

Frank Drummond

Second Committee Member

Christopher Campbell

Third Committee Member

Stellos Tavantzis

Abstract

Little is known of the genetic structure and variability of wild fields, or of the dramatic differences in yield among individuals or clones of lowbush blueberry (Vaccinium angustifoliiim Ait.) in Maine. Expressed Sequence Tag-Polymerase Chain Reaction (EST-PCR) markers, originally developed in Vaccinium corymbosum L., were shown to be very effective at both interspecific and intraspecitic genetic discrimination of clones of lowbush. Importantly, the only known pedigree of four cultivars of V. angustifoliiim grouped out as expected in a genetic similarity dendrogram based on these markers. Thus, EST-PCR markers were used to infer spatial genetic structure of four lowbush blueberry fields at three spatial scales: 1) within apparent clones, 2) among clones within a field, and 3) among fields. First, high intraclonal genetic homogeneity was found, indicative of a fairly tight, phalanx clonal architecture with no evidence of within clone seedling establishment. Second, several analyses revealed no significant correlation between genetic and physical distance among clones within fields. Third, however, genetic differentiation was found via AMOVA (Q>pt = 8.4% ) among the four fields ranging from 12.5-65 km apart. Long distance dispersal of seeds via migratory birds was cited as a possible cause. EST-PCR markers were also used, along with two designs of field hand crosses ('pairwise' and diallel), to investigate the possible genetic factors contributing to yield variations among clones. In the pairwise study, both near and far male donors (~300 m apart) were randomly related to the focal female (range: 0.308-0.765 genetic similarity). Genetic similarity of parents had no effect on yield in crosses overall except when self crosses were included (similarity of one). Self-fertility rates, however, were significantly predictive of outcross yields. A large range and magnitude (compared to highbush blueberry) in genetic load, as estimated by the calculation of 'lethal equivalents' from selfing to outcross ratios, was found. General (GCA) and specific (SCA) combining abilities were significant at the whole model level and modestly high narrow-sense heritability estimates were found for all three yield traits. It was concluded that phenotypically screening for self-fertile clones could be used to identify germplasm candidates for filling in bare areas of fields.

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