Comparative responses to water stress in stay-green, rapid- and slow senescing genotypes of the biomass crop, Miscanthus

Although hybrids of the perennial rhizomatous grass Miscanthus give high yields under irrigation, their use as a biomass crop in many locations is limited by inadequate water availability. Here, the effects of reduced water availability on growth are reported for three Miscanthus genotypes with differing responses to drought. In a controlled environment experiment during a drought treatment M. sinensis hybrid (Sin-H6) had no detectable photosynthesis and negligible leaf conductance, whereas M. x giganteus (Gig-3) continued to photosynthesize and transpire but it shed leaf area through senescence. A M. sacchariflorus line (Sac-5) was generally intermediate in its response. Measurements on 3-y-old stands of Gig-3 and Sin-H6 in the field during a short summer drought in August 1999 confirmed the controlled environment observations. Stay-green characteristics in Sin-H6 appeared to rely on tight control of transpiration through lowered leaf conductance, although the highest leaf ABA concentrations were not found in this genotype. Stay-green genotypes, such as Sin-H6, are likely to be important for further breeding of Miscanthus because they appear to make the most effective use of available water.