How low can you go?—Rhizome and shoot frost tolerance in miscanthus germplasm

• Large variation in frost tolerance was observed in a miscanthus germplasm collection.
• Rhizome lethal temperature ranged between −0.4 °C and −5.9 °C depending on genotype.
• M. sinensis and M. sinensis x sacchariflorus genotypes tended to be more frost tolerant.
• Early flowering genotypes and genotypes from colder regions were more frost tolerant.

The biomass crop M. x giganteus is susceptible to frost stress. Frost can kill rhizomes during winter or damage new shoots in early spring. To develop new miscanthus varieties with improved rhizome and shoot frost tolerance, a large germplasm collection must first be screened for these traits. We therefore determined the temperature at which 50% of the rhizomes are killed (LT50) in 95 miscanthus genotypes including M. sinensis, M. sacchariflorus, M. x giganteus and interspecific hybrid genotypes. The LT50 in the collection ranged between −0.4 and −5.9 °C, while the average LT50 for M. x giganteus was −2.6 ± 0.3 °C. On average LT50 was −3.5 ± 0.1 °C in M. sinensis, −2.6 ± 0.3 °C in M. sacchariflorus and −3.9 ± 0.2 °C in the M. sinensis x sacchariflorus hybrids. Rhizome frost tolerance was correlated to the timing of flowering and senescence but not to rhizome moisture content. Wide variation in shoot damage was observed in a field trial after a cold spell in early spring. Determination of apex height indicated that the shoot apex was probably still below ground when frost occurred, explaining the rapid recovery of damaged shoots after the frost event. This study is the largest screening of rhizome and shoot frost tolerance in miscanthus reported to date and demonstrates the availability of frost tolerant genotypes in miscanthus breeding material, potentially supporting the development of new frost tolerant varieties.