Adaptation to a 'home' site by white clover (Trifolium repens) in sown swards in Uruguay

Climatic and soil conditions in Uruguay are marginal for white clover (Trifolium repens L.). Plants were collected from four sites, in different parts of the country, multiplied vegetatively, and the populations planted into each of the four sites. Plant survival and internode length (indicating growth potential) were recorded at intervals during the 55-week period after planting. On the site with the highest annual rainfall and lowest summer water deficit, one fifth of the plants survived at least 55 weeks, whereas on the site with the highest annual evaporation almost all the plants had died within 20 weeks. There was some evidence of adaptation to a ‘home’ site in both plant survival and growth potential. Thus, on three of the four sites, populations from the ‘home’ site survived better than the average of the non-‘home’ populations. Also, internode length was greatest (9·5 mm on average, compared with a mean of 5·6 mm for the experiment as a whole) in a population from a site with soil relatively high in available P, when planted into its ‘home’ site. Plant breeders could consider producing different white clover cultivars to suit different conditions of moisture supply and available P.