Can miscanthus C4photosynthesis compete with festulolium C3photosynthesis in a temperate climate?

Miscanthus, a perennial grass with C4photosynthesis, is regarded as a promising energy crop due to its high biomass productivity. Compared with other C4species, most miscanthus genotypes have high cold tolerances at 14 °C. However, in temperate climates, temperatures below 14 °C are common and our aim was to elucidate cold tolerances of different miscanthus genotypes and compare with a C3perennial grass – festulolium. Eleven genotypes ofM. sacchariflorus, M. sinensis, M. tinctorius, M. × giganteusas well as festulolium were grown under warm (24/20 °C, day/night) and three under cold (14/10 °C, 10/8 °C and 6/4 °C) conditions in a controlled environment. Measurements of photosynthetic light response curves, operating quantum yield of photosystem II (ΦPSII), net photosynthetic rate at a PAR of 1000 μmol m−2s−1(A1000) and dark‐adapted chlorophyll fluorescence (Fv/Fm) were made at each temperature. In addition, temperature response curves were measured after the plants had been grown at 6/4 °C. The results showed that two tetraploidM. sacchariflorusand the standard triploidM. × giganteus cv. Hornum retained a significantly higher photosynthetic capacity than other miscanthus genotypes at each temperature level and still maintained photosynthesis after growing for a longer period at 6/4 °C. Only two of five measured miscanthus genotypes increased photosynthesis immediately after the temperature was raised again. The photosynthetic capacity of festulolium was significantly higher at 10/8 °C and 6/4 °C than of miscanthus genotypes. This indicates that festulolium may be more productive than the currently investigated miscanthus genotypes in cool, maritime climates. Within miscanthus, only oneM. sacchariflorusgenotype exhibited the same photosynthetic capacity as Hornum at both cold conditions and when the temperature was raised again. Therefore, this genotype could be useful for breeding new varieties with an improved cold tolerance vis‐a‐vis Hornum, and be valuable in broadening the genetic diversity of miscanthus for more widespread cultivation in temperate climates.