Genotypic variation in chilling tolerance in miscanthus germplasm

Early emerging miscanthus varieties, tolerant to the low temperature stress typical of early spring, may have a yield advantage over late emerging ones in temperate regions. A longer growing season allows the interception of more light energy and can potentially result in the production of more biomass. In addition, the availability of miscanthus varieties with a high degree of chilling tolerance might allow cultivation in colder, continental climates. Therefore we evaluated to what the extent cold tolerant genotypes with a high yield potential are available to European breeders by screening of the OPTIMISC germplasm collection in controlled environments and in the field. In growth chambers, we determined the reduction of the leaf growth under chilling stress compared to control conditions. A reduction of between 18 and 68% was observed among the 54 genotypes evaluated. Furthermore, spring growth was measured intensely in 2014 and 2015 on a field trial of 104 genotypes in Melle, Belgium. These genotypes differed substantially in day of emergence, growth rate and cold stress tolerance. A large range was observed, with the earliest genotypes emerging over one month earlier than the late genotypes. Stem extension rates in spring varied between 8 and 27 mm day-1. Base temperature for growth of the genotypes in the collection was determined both in growth chambers as a reference (4 genotypes) and in the field trial. Additionally, base temperature was determined using spring growth measurements of 11 genotypes from the six OPTIMISC multilocation field trials spread across Europe. Overall, tested genotypes showed a large variation in cold tolerance characteristics. M. x giganteus proved to be of average cold tolerance. Cold tolerant genotypes were found in M. sinensis, M. sacchariflorus and M. sinensis x sacchariflorus hybrids. At the end of the growing season biomass yield was determined and correlation with chilling tolerance was calculated.