Water use efficiency and associated physiological traits of nine naturalized white clover populations in Chile

P>Water use efficiency (WUE) of nine naturalized white clover (Trifolium repens L.) populations was evaluated to select parental genotypes for future breeding programmes and to identify associated physiological traits that could be used as selection criteria. A greenhouse experiment was carried out during the spring of 2007 in Chillan, Chile (36 boolean OR 03'S, 72 boolean OR 07'W). The nine naturalized populations plus two controls were planted in pots containing soil as substrate. The plants were grown under two soil water treatments: with water stress (-1 MPa) and without water stress (-0.01 MPa). The experiment was arranged in a randomized complete block design with three replicates. Transpirated water (T) was recorded daily by weighing the pots, shoot DM (leaves + petioles + stolons) production was measured and WUE was calculated (shoot DM/T). Stomatal conductance (gs), chlorophyll content, relative water content, leaf 13C isotopic discrimination, canopy temperature and stolon water potential were also evaluated. The WUE varied significantly (P = 0.05) among populations and increased under drought conditions because of gs reduction. A high WUE was associated with populations that had a low leaf area DM investment and high stolon DM investment.