Genotypic variation in the frost tolerance of miscanthus rhizomes

Miscanthus x giganteus, the most widely planted miscanthus clone in Europe, often shows poor overwintering in most cold, northern locations. This is most likely the result of frost damage to the rhizomes. Breeding new miscanthus varieties with higher rhizome frost tolerance would allow expansion of the geographical cultivation range to colder locations. We have screened a large collection (>100) of miscanthus genotypes, comprising M. x giganteus, M. sinensis, M. sacchariflorus and M. sinensis x sacchariflorus hybrids, for rhizome frost tolerance. Rhizomes of field-grown plants were dug up in the winter months, sealed in plastic bags and subjected to frost treatments (-2, - 3, -4, -6°C) in a temperature-controlled bath. The rhizomes were then allowed to grow at optimal temperature and the LT50 was determined. LT50 ranged between 0 and -6°C. In general, M. sinensis and hybrid genotypes were the most frost tolerant while M. sacchariflorus genotypes were the most susceptible. Several of the genotypes screened were more frost-tolerant than M. x giganteus, but the range of LT50 values obtained for this large miscanthus collection was rather small compared to other crops. The more frost tolerant genotypes could be used as parent in the breeding of new varieties with a substantially higher frost tolerance than M. x giganteus.