Quantifying Spatial and Temporal Genotypic Changes in White Clover Populations by RAPD Technology
2001
Gustine, David L. | Sanderson, Matt A.
In established white clover (Trifolium repens L.) populations, seedling recruitment is rare and plants spread by clonal growth, which could lead to low intraspecific genetic diversity. To assess how populations of white clover maintain high genetic variability in grazed swards during a growing season, we examined spatial and temporal changes in white clover clones by identifying genotypes by RAPD (random amplified polymorphic DNA) profiles. Trifoliate leaf samples were taken from plants at up to 37 specific sampling points in each of four 2.8-m² permanent quadrats in a grazed pasture from April to October 1997. RAPD profiles (genotype) based on 28 markers were determined for genomic DNA prepared from leaf samples. The number of sampled clones per quadrat ranged from zero to 10 and the sampled members per clone ranged from two to 34 over the growing season. Some clones were found more than once. During the study, numbers of clonal members increased or decreased, clones were found on one to three dates, and clones were found in one to two quadrats. The clonal diversity index D (probability that any two sampled plants have different genotypes) ranged from 0.89 to 0.99 for the eight dates, showing that genotypic diversity of populations was affected by number of clones and number of clonal members. We report here the first use of dominant RAPD markers to document dynamic changes of white clover population structure. These data show that white clover clones undergo dynamic spatial and temporal variability at a local scale, which accounts for much of the genetic diversity within field populations.
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