Using leaf-mark material to monitor the morphology of white clover (Trifolium repens L.) at the clone and ramet level in grazed swards

Leaf markings are widespread in Trifolium spp. White clover (T. repens L.) material has been produced at the Institute of Grassland and Environmental Research (IGER) Aberystwyth, UK, which demonstrates the 'filled - V' leaf mark as a subtle but clearly identifiable mark with little seasonal variation in expression. This paper describes how a population of genotypically identical individual white clover plants (clones), created from this material, can be used in grazed swards to monitor changes in morphology at the clone and ramet level. In a pilot experiment, the effect of a late silage cut on the white clover component of grazed mixed swards was investigated. Leaf-mark plants were introduced into known positions in a grass/clover sward in 1997 and monitored during 1998 under two grazing regimes: (1) continuous grazing to a sward surface height of 4 cm (treatment G); and (2) grazing, followed by a single late-season silage cut, a brief rest period, and a return to autumn sheep grazing (treatment GRG). The GRG treatment had a significant and rapid effect, producing larger clones with a larger number of ramets and higher proportions of complex ramets than the G treatment. As ramet complexity increased the treatment effect intensified, resulting in a four-fold increase in clone size, together with an enhanced ability to spread into the sward. The GRG treatment allowed a more widespread dispersal of individual units and this is likely to enhance the opportunity for ramets to encounter favourable micro-environments for survival and growth, The benefits and limitations of the procedures are discussed. (C) 2001 Annals of Botany Company.