Breeding for Improved Drought Tolerance in Red Clover (Trifolium pratense L.)
Four red clover (Trifolium pratense L.) and two Medicago truncatula L. varieties were compared for their response to a two-week drought stress at three, five, and seven weeks of age in a controlled environment. The clovers had greater (P<0.05) combined crown and root biomass, and shoot biomass compared to the medics at 80, 30, and 15% field capacity (FC). Combined crown and root weights of the medics did not change as moisture stress increased, whereas the red clover crown and root weights declined. For both species, shoot weight decreased as moisture stress increased. Three cycles of recurrent selection at 30% FC soil moisture were conducted within three populations of red clover. Evaluation of the selection cycles at 15 and 30% FC revealed there was increased combined crown and root weight in one population and increased shoot weight in two of the populations. However, this biomass increase was also detected in non-stress conditions (80% FC). Selection for plant vigour under reduced soil moisture conditions resulted in improved growth in both moisture limited and non-limiting conditions.