EliteTree™: an advanced biomass tree crop technology that features greater wood density and accelerated stem growth

Due to wood's potential for large-scale commercial production of biofuels, a rapid increase in the use of wood as a source of energy is expected as policies promoting greater use of renewable energy are adopted globally. However, the economics of purpose-grown tree feedstocks for energy show that these production systems are not financially viable without improvement in the base growth rate. Conventional breeding programs have produced willow and poplar clones that show potential for rapid growth, but current top-performing clones do not grow fast enough for profitable biofuel production. Genetic manipulation of secondary wall biosynthesis is the most direct path to resolving this growth barrier. To that end, we developed an innovative biomass tree crop technology, EliteTree, that results in greater wood density and accelerated growth of stems. This technology is built on overexpression of Gibberellin 20-oxidase to increase plant stem growth in both height and diameter and increase lignocellulosic biomass accumulation through overexpression of the transcription factor MYB46, which is a master regulator for secondary wall biosynthesis. EliteTree technology uses 2A-mediated bicistronic gene expression, with our proprietary utility promoter DX15, such that the genetic manipulation is limited to wood tissue, yielding transgenic poplars with xylem-specific co-expression of MYB46 and PdGA20ox1. The development of faster growing elite tree genotypes with increased wood density and growth rates will pave the way for truly sustainable and economically viable bioenergy/biofuel production using short rotation tree plantations, and ultimately will lessen carbon emissions and has the potential to revitalize rural economies. (C) 2017 Society of Chemical Industry and John Wiley & Sons, Ltd