A survey of the genetic diversity in populations of white clover, Trifolium repens with a focus on South-Western Europe : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Plant Molecular Biology at Massey University, Palmerston North, New Zealand
Trifolium repens (white clover), is an allotetraploid, formed from the cross of putative parents T. pallescens and T. occidentale. The purpose of this study was to analyse intra-species genetic diversity of T. repens among and within populations from the Mediterranean, UK, continental Europe, North Africa, and the near East. This allowed light to be shed on the origins and radiation of the species. It was hypothesized from current distributions of the putative parents, and T. repens that an origin for the species was within South-Western Europe.
A survey of genetic diversity was conducted through PCR and direct sequencing of the chloroplast trnL intron, and a chloroplast internal repeat region (IRB21NE) (300 plants) and from the nuclear rDNA, ITS regions of the nucleolar organizing region, (NOR), (327 plants). The interpretation of results was complicated by the spread of commercial varieties over the top of natural populations of T. repens.
Diversity was greater for ITS pattern types (45) than for chloroplast pattern types (5). Maximum chloroplast diversity was found in Portugal/Spain. Pockets of ITS diversity were observed in, Portugal/Spain, North Africa, UK (Kent landrace) and Northern/North-Western Europe. Within the natural distribution zone for the species two chloroplast lineages and three main nuclear lineages described the majority of the observed variation. However a novel nuclear lineage was observed in north/north-western Europe. Spain and Portugal differed in their predominant ITS lineages, as did Morocco and Algeria from each other.
The diversity in chloroplast data was consistent with an origin in Portugal and Spain. ITS diversity also supported this, but the presence of other areas of ITS diversity, gave a complex pattern that requires further study.