Architectural and genotypic variation in the clonal shrub Taxus canadensis as determined from random amplified polymorphic DNA and amplified fragment length polymorphism

Abstract

Canada yew (Taxus canadensis Marsh.) is a clonal species with two types of ramets. The most common type has bilateral symmetry and alternate branching. The radial symmetry and opposite branching of the rarer type are similar to the architecture expressed in a young plant grown from seed. Architectural analysis was conducted on four colonies of increasing age and size. A genetic analysis using random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) was conducted on 122 ramets, 93 sampled from nine colonies from a single population, 24 from eight other populations, and five from other Taxus species. Analysis of the architectural development sequence shows that yew follows the same architectural model as, for example, species of Abies or Picea. This model constitutes a level of organization intermediate between that of the ramet and of the genet. The molecular analyses confirm the greater variability of AFLPs over RAPDs and indicate that architecture is not directly related to genotypic variation. Ramets with radial symmetry have slightly higher genetic variation, on average, than ramets with bilateral symmetry with 95% degree of confidence. The molecular analyses show that the level of resolution of the AFLPs is adequate to characterize 98% of the ramets of a colony. Between pairs of physically connected ramets, some random genotypic differences are observed, supporting the hypothesis of genetic mosaicism in plants, due to somaclonal variations.Key words: architecture, clonal plant, intraclonal variation, molecular markers, somaclonal mutations.