Journal of Heredity 2004:95(2):172-176
© 2004 The American Genetic Association
Brief Communication |
Somatic Mutations at Microsatellite Loci in Western Redcedar (Thuja plicata: Cupressaceae)
From Natural Resources Canada, Canadian Forest Service, Atlantic Forestry Centre, P.O. Box 4000, Fredericton, NB, E3B 5P7, Canada (O'Connell), and the Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia, V6T 1Z4, Canada (Ritland). We thank S. Otto for discussion and comments on an earlier version of this manuscript and J. Russell for his help collecting samples. This work was supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) research grant to KR, and an NSERC postgraduate scholarship and Izaak Walton Killam predoctoral Fellowship to LMO.
Address correspondence to Lisa M. O'Connell at the above address, or e-mail: loconnel{at}nrcan.gc.ca.
A per-generation somatic mutation rate for microsatellites was estimated in western redcedar (Thuja plicata, Donn ex D. Don.: Cupressaceae). A total of 80 trees representative of the average size and age of reproductive trees were sampled in four natural populations in southwestern British Columbia. Samples of bulked haploid megagametophytes were collected from two or three positions on each tree, assuming that the collections were far enough apart that the same mutant sector was not sampled twice. All samples were genotyped at eight microsatellite loci. A single mutation corresponding to a stepwise increase in one dinucleotide repeat was detected. The estimated mutation rate for microsatellites was 6.3 x 10–4 mutations per locus per generation (or 3.1 x 10–4 per allele per generation), with a 95% confidence interval of 3.0 x 10–5 to 4.0 x 10–3 mutations per locus. Somatic mutations can contribute to a greater mutational load in trees, as compared to shorter lived plants, and genotypic mosaics within an individual have important implications for plant defense strategies and plant evolution.