Chilling tolerance and early vigour-related characteristics evaluated in two Miscanthus genotypes

A long growing season, mediated by the ability to grow at low temperatures early in the season, can result in higher yields in biomass of crop Miscanthus. In this paper, the chilling tolerance of two highly productive Miscanthus genotypes, the widely planted Miscanthus x giganteus and the Miscanthus sinensis genotype 'Goliath', was studied. Measurements in the field as well as under controlled conditions were combined with the main purpose to create basic comparison tools in order to investigate chilling tolerance in Miscanthus in relation to its field performance. Under field conditions, M. x giganteus was higher yielding and had a faster growth rate early in the growing season. Correspondingly, M. x giganteus displayed a less drastic reduction of the leaf elongation rate and of net photosynthesis under continuous chilling stress conditions in the growth chamber. This was accompanied by higher photochemical quenching and lower nonphotochemical quenching in M. x giganteus than that in M. sinensis 'Goliath' when exposed to chilling temperatures. No evidence of impaired stomatal conductance or increased use of alternative electron sinks was observed under chilling stress. Soluble sugar content markedly increased in both genotypes when grown at 12A degrees C compared to 20A degrees C. The concentration of raffinose showed the largest relative increase at 12A degrees C, possibly serving as a protection against chilling stress. Overall, both genotypes showed high chilling tolerance for C-4 plants, but M. x giganteus performed better than M. sinensis 'Goliath'. This was not due to its capacity to resume growth earlier in the season but rather due to a higher growth rate and higher photosynthetic efficiency at low temperatures