Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 3/12/2010
Publication Date: 4/21/2010
Citation: Bell, D.J., Rowland, L.J., Stommel, J.R., Zhang, D., Drummond, F.A. 2010. Yield variation among clones of lowbush blueberry (Vaccinium angustifolium Ait.) as a function of kinship, self-compatibility, and combining ability. BARC Poster Day.
Technical Abstract: Lowbush blueberry (Vaccinium angustifolium Ait.) is an unusual agricultural crop of northeastern North America. Unlike most fruit crops, improved varieties have not been developed and planted. Instead, wild fields, which arose from natural colonization over long periods of time through animal-mediated seed dispersal, are intensively managed with the goal of maximizing yields. Unique genetic individuals (or clones) of lowbush range greatly in yield, however, even though they set and mature fruit under optimum conditions. Discovering the possible genetic causes of these differences is the focus of this study. Lowbush blueberry has been typically characterized as self-infertile, and inbreeding depression has been hypothesized as a possible contributing factor to yield reduction in crosses between closely related clones. However, this has not been testable previously since the genetic relationships among breeding partners (near-neighbor pollen exchangers from honey bee pollination) are unknown. We have used recently developed EST-PCR (Expressed Sequence Tag – Polymerase Chain Reaction) molecular markers to estimate the genetic similarity of experimental clones, together with two designs of field hand pollinations, a touching neighbor design and a factorial diallel, to test: 1) whether genetic relationship of breeding partners affects yield, 2) whether self and outcross yield ratios are related, and 3) whether combining abilities help in explaining the kinds of genetic action (additive or dominance) which may be involved. In our three year study, we found no evidence of within field spatial genetic structure, i.e. the distribution of genotypes within fields was random. Furthermore, even in comparing crosses between closely related clones to far related (range: ~ 0.308 – 0.765 similarity), no significant effect by genetic similarity was found. Our measurements on 27 clones revealed a markedly higher incidence of self-fertile clones than has traditionally been reported. Moreover, self-fertility was found to be a significant predictor of outcross yield. The diallel crossing design revealed significant general combining ability (GCA) and specific combining ability (SCA). Due to the preponderance of GCA over SCA, narrow-sense heritability (h2) estimates for three post-pollination yield traits (proportion fruit set, mean mature seed per pollination, and mean berry weight) fell in the moderate range indicating that parental traits could be recovered by screening for parental clones with high yield phenotypes, notably self-fertile clones. Finally, we noted specific combinations of crosses (SCA) produced synergistic effects in yield indicating that seed families from these crosses and self-fertile clones could be produced to fill in bare areas of fields and, thus, increase yield for growers.