Siberian Miscanthus sacchariflorus accessions surpass the exceptional chilling tolerance of the most widely cultivated clone of Miscanthus x giganteus

摘要

Chilling temperatures (0–15°C) inhibit photosynthesis in most Csub4/sub grasses, yet photosynthesis is chilling tolerant in the ‘Illinois’ clone of the Csub4/sub grass Miscanthus x giganteus , a candidate cellulosic bioenergy crop. M. x giganteus is a hybrid between Miscanthus sacchariflorus and Miscanthus sinensis ; therefore chilling‐tolerant parent lines might produce hybrids superior to the current clone. Recently a collection of M. sacchariflorus from Siberia, the apparent low temperature limit of natural distribution , became available, which may be a source for chilling tolerance. The collection was screened for chilling tolerance of photosynthesis by measuring dark‐adapted maximum quantum yield of PSII photochemistry ( Fsubv/sub/Fsubm/sub ) on plants in the field in cool weather. Superior accessions were selected for further phenotyping: plants were grown at 25°C, transferred to 10°C (chilling) for 15?days, and returned to 25°C for 7?days (recovery). Two experiments assessed: (a) light‐saturated net photosynthetic rate ( Asubsat/sub ) and operating quantum yield of PSII photochemistry (ΦsubPSII/sub), (b) response of net leaf COsub2/sub uptake ( A ) to intercellular [COsub2/sub] ( csubi/sub ). Three accessions showed superior chilling tolerance: RU2012‐069 and RU2012‐114 achieved A subsat/sub up to double that of M. x giganteus prior to and during chilling, due to increased csubi/sub ‐ saturated photosynthesis ( V submax/sub). RU2012‐069 and RU2012‐114 also maintained greater levels of ΦsubPSII/sub during chilling, indicating reduced photodamage. Additionally, accession RU2012‐112 maintained a stable A subsat/sub throughout the 15‐day chilling period, while A subsat/sub continuously declined in other accessions; this suggests RU2012‐112 could outperform others in lengthy chilling periods. Plants were returned to 25°C after the chilling period; M. x giganteus showed the weakest recovery after 1?day, but a strong recovery after 1 week. This study has therefore identified important genetic resources for the synthesis of improved lines of M. x giganteus , which could facilitate the displacement of fossil fuels by cellulosic bioenergy.