Fine-scale spatial genetic structure associated with Vaccinium angustifolium Aiton (Ericaceae)

Authors: Bell, Daniel; Rowland, Lisa; DRUMMOND, FRANK - University Of Maine

Submitted to: International Journal of Modern Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2012
Publication Date: 10/1/2012
Citation: Bell, D.J., Rowland, L.J., Drummond, F.A. 2012. Fine-scale spatial genetic structure associated with Vaccinium angustifolium Aiton (Ericaceae). International Journal of Modern Botany. 2(4):72-82.

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. Lowbush blueberry is pollinated by rented honey bees which tend to fly short distances, thus plants tend to be pollinated by themselves or nearby neighboring plants. Crosses between individual blueberry plants that are too closely related can result in low yields due to inbreeding. If the distribution of individuals in fields is such that closely related individuals tend to cluster together in patches within fields, then this could explain the low yield of some plants. Here we have used molecular markers to examine genetic relatedness of approximately 100 individual plants closely spaced within one blueberry field in Maine, testing whether the more closely spaced individuals are more closely related. We found that in general most of the individuals are not highly related to their near neighbors. However, we did find a few clusters of highly related individuals. These patches of genetically similar individuals could possibly explain some of the yield differences. This information will be useful to other scientists interested in improving yields in lowbush blueberry.

Technical Abstract: Lowbush blueberry fields in Maine are comprised of long-lived individuals, termed clones, which are wild in origin. Fields are naturally formed. It is assumed that colonization occurs by animal dispersed seed over long periods of time. Pollination is by bees that are documented as having localized short distance within and between plant flight patterns. This study tested, at the within field scale, if a positive fine-scale spatial genetic structure (SGS) could be detected. Using a ‘contiguous’ design (all touching clones within 0.35 ha of one field) and a ‘neighborhood’ design (a few focal clones in two fields surrounded by their touching neighbors) we found, using EST-PCR (Expressed-Sequence-Tag-Polymerase Chain Reaction) markers, through non-parametric, distance based methods, significant, positive spatial autocorrelation (SA) within the first distance class of 7.5 meters (r = 0.067 + 0.022; p > 0.001). Two-dimensional local spatial autocorrelation also revealed in both designs significant, positive SA in clusters of clones within 15m apart. Particularly, in the ‘contiguous’ design, 32 of the 94 clones were found within the proportion genetic similarity range of 0.53 – 0.72 (the range expected with dominant markers for half to full-sib relationships (0.65 – 0.80)). These related clusters displayed a ‘patchy’ architecture across the study area interspersed with the balance of 62 clones following a random distribution. In the ‘neighborhood’ design, AMOVA revealed significant between field (Frt = 1.6%) and within field (Fpr = 3.7%) genetic differentiation. Two possible ecological and evolutionary hypotheses are discussed that render insight into the dynamics of how these fields developed and how the high levels of genetic diversity are maintained.