Genetic Resources and Crop Evolution 47: 81–91, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. 81 Genetic variation of five species of Trifolium L. from south-west Turkey Sarita Jane Bennett Co-operative Research Centre for Legumes in Mediterranean Agriculture (CLIMA) and Faculty of Agriculture, University of Western Australia, Nedlands, Western Australia 6907. Australia Received 31 December 1998; accepted in revised form 7 April 1999 Key words: adaptation, genetic resources, edaphic variation, multivariate analysis, Trifolium Abstract Following a legume collection mission to south-west Turkey in 1996, five species of Trifolium were analysed for genetic variation within and between species in eleven morphological and flowering characters. The five species included two outcrossing species, T. michelianum and T. resupinatum, and three inbreeding species, T. clypeatum, T. glomeratum and T. tomentosum. The genetic diversity found was related to climate and edaphic factors. All five species showed significant amounts of genetic differentiation between sites and the species could be separated morphologically by principal components analysis and cluster analysis. The most significant source of genetic variation was found to be related to geographical distribution with those species which were widely distributed across south-west Turkey exhibiting much greater amounts of genetic variation between sites, than those which had a narrow distribution. The breeding system was found to be less important, but only the morphology of the outbreeding species showed any environmental clines in relation to climate. A multiple regression analysis was computed to estimate the effect of growing season on the days to flowering of each of the species. Introduction The Mediterranean is the centre of diversity of the genus Trifolium (Zohary & Heller, 1984) with 110 spe- cies from seven of the eight sections present. Turkey is the Mediterranean country with the richest diversity of Trifolium with nearly 100 species (Cocks, 1993). The rich genetic resources in Turkey have played an important part in the history of agriculture as it is the centre of origin of many of the cultivated crops grown today. It continues to provide a wealth of material for improving the agricultural production of temperate world agriculture in the form of primitive landraces, wild crop relatives and other wild species (Tan, 1996). Pasture legumes are an important component of the agricultural system in southern Australia, increasing productivity in areas with a mediterranean climate (Ewing et al., 1989). However the number of species in common use is limited as is the genetic diversity of many of those species. T. subterraneum L., however, has been shown to contain almost as much variabil- ity as the original Mediterranean populations (Cocks, 1992), with many divergent strains existing as a result of hybridisation between cultivars (Rossiter & Collins, 1988a, 1988b). The most widely utilised species are T. subterraneum (subterranean clover), Medicago poly- morpha L. (burr medic) and M. truncatula Gaertn. (barrel medic), but many edaphic niches exist where these species have not been successful (Howieson & Loi, 1994). A number of alternative species have been introduced in the last ten years which have been suc- cessful in some of these more difficult niches, such as Ornithopus compressus L. (serradella) for acid, sandy soils (Revell, 1992), Biserrula pelecinus L. for low rainfall, acid duplex soils (Howieson et al., 1995) and T. michelianum Savi (balansa clover) and T. re- supinatum L. (Persian clover) for waterlogged areas where subterranean clover will not persist (Rowe & Craig, 1992; Craig 1989). Many other legume gen- era and species within the genus Trifolium may be alternatives for these and other difficult niches. There is a need to introduce new species more systemat- ically than in the past to increase the potential of identifying legumes that will become successful pas-