Using microsatellite DNA to determine whether American Hazelnut Clumps are multiclonal

Abstract

We have been selecting high yielding American hazelnut (Corylus americana) from wild populations. Because hazelnuts tend to have a spreading growth form, it was unclear whether phenotypic variation among the individual stems of a clump was due to multiple genotypes which had grown together. This would significantly complicate selection. In order to determine if these bushes were single genotypes, we collected leaf samples from the four cardinal directions from each of 23 high producing stems. These were analyzed for 4–6 microsatellite loci. We determined that of the 23 selections, 5 were composed of more than one genotype. Additionally, one clump had one allele on one direction that was different (likely allele dropout from a heterozygote where one allele did not amplify correctly). Overall, the majority of clumps (78 %) were composed of a single genotype. This suggests that selecting at the level of “clump” is viable. Additionally, we noticed that within our selection sites, certain plants seemed to function only as males (produced male catkins but seldom produced female flowers) while others produced copious female flowers and subsequently nuts. Within one site, we selected 20 hazelnuts with both male and female flowers and 19 with only male flowers. Using the same microsatellite techniques for 10 loci, we assessed whether there were obvious genetic differences between these types of plants. Overall, there was no difference between plants that bore female flowers and those that did not. Microsatellite DNA techniques are becoming a more useful tool for selection of potential agroforestry crops from wild populations.