Low Temperature Performance of Leading Bioenergy Crops Utilizing the C4 Photosynthetic Pathway

The use of bioenergy has been considered one of the most important solutions for the reduction in the dependence on fossil fuels and to mitigate global climate change. C4 perennial grasses stands as the best alternative for biofuel feedstock and Miscanthus x giganteus has shown outstanding performance in cool climates. In addition, sugarcane has a history of high productivity and success in the biofuel industry of Brazil. The high photosynthetic rate at low temperature (14º to 20ºC) and radiation use efficiency of M. x giganteus allow this plant to build a vast canopy early in the spring, allowing it to intercept high amounts of solar radiation once temperature rise in summer, obtaining high yields of biomass by the end of growing season. It is unclear, however, how Miscanthus will tolerate the severe winter cold and frequent episodic frost in the spring of higher latitudes, like Canada. Here, I show that rhizomes of diploid Miscanthus can tolerate temperatures above -14ºC if sub-zero acclimation is allowed, while allopolyploid Miscanthus are tolerant to temperatures above -6.5ºC. Also, in contrary to M. sinensis, shoots of Miscanthus hybrids were killed when exposed to sunlight at temperatures below 10ºC in the spring. However, triploid Miscanthus showed great recovery and three weeks later plants had a vast and closed canopy while M. sinensis plants had a poor canopy. Lastly, I show that upland and lowland Hawaiian sugarcane grown at two moderate temperatures have little variation in temperature response and acclimation to low temperature. Because of its high productivity, Miscanthus should be considered in areas where it can securely be grown. According to the results found here, rhizomes of diploid Miscanthus have the potential to be grown up to 60ºN, but the frequency of episodic chilling events should also be taken into consideration. Here, I show that the genepool of the Miscanthus genus has the potential to increase cold tolerance in the most productive lines, which will increase the range for this crop. Sugarcane is still restricted to tropical and subtropical zones, but higher cold tolerance can be achieved by hybridizing this plant with Miscanthus.Ph.D