Genetic differentiation in white clover(Trifolium repens)populations during 8 years of contrasting phosphorus supply in New Zealand hill country

Abstract

Genetic differentiation under the selection force of variable soil P availability was measured in populations of two white clover cultivars introduced to a grazed, low fertility grassland site. The resulting mixed grass-clover pastures subsequently received contrasting levels of phosphorus (P) fertiliser for 8 years. Afield-based reciprocal transplant experiment and two controlled-environment experiments were conducted using plants removed from the 8-year field experiment and appropriate controls to test the hypotheses that: (1) genetic differentiation occurred within the white clover populations in response to variation in P supply; and (2) surviving plants which demonstrated genetic differentiation under high-P conditions would continue to do this when grown in mixtures with plant material removed from unsown pasture.

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

“…The longest internodes were on transplants derived from Engels, the site with the highest available P in the soil, transplanted into their ' home ' site. This, together with evidence presented by Wedderburn et al (2005), suggests that a sown white clover population is more likely to retain P-responsive genotypes over a period of years on sites with relatively high available soil P (Engels in this study) than on sites with much lower available soil P (such as Berrutti and Sanz). This suggests in turn that plant breeders might consider producing some cultivars intended for low P soils (typical of Uruguay) and others for sites with higher available P. In the latter case, material should be selected from sites with relatively high available soil P, so that the potential response to P is likely to be high.…”

“…Pastures in Uruguay commonly do not receive lime or fertilizer, and both soil pH and available P are likely to be below optimum for white clover, adding to the marginal nature of the environment. Low available P in the soil may lead to the loss of P-responsive genotypes in a white clover population (Wedderburn et al 2005), thus producing a population with a low potential response to P.…”