Improving Arundo donax Biomass through RNAi Induced Flowering Delay

Grasses are traditionally ideal lignocellulosic feedstocks due to their high productivity, environmental adaptability, low economic cost, and lack of competition with food crops. Of particular interest among grass species is Arundo donax L., the giant reed, which is an invasive perennial rhizomatous grass with a high biomass yield. Arundo seeds are sterile, making conventional breeding impossible; therefore, genetic transformation is necessary in order to improve crucial agronomic traits. The goal of this study was to increase the biomass potential of Arundo by delaying flowering through RNAi silencing of florigen genes. Previous studies, have demonstrated that the transition between the vegetative and reproductive stages of the plant can be significantly extended through genetic modification of florigens. Specifically, our goal is to improve the biomass yield by silencing the Flowering Locus T (FT) gene in Arundo donax. Due to the lack of a whole genome sequence for Arundo, an FT-like sequence (650 bp) and was isolated from genomic DNA by TAIL-PCR, and fragments of 250 bp were amplified for RNAi. The vector for RNAi was synthesized to include a hygromycin (HYG) resistance gene and the phloem specific promoter (pRPPP16). HYG resistance was chosen for selection because Arundo calli are resistant to common herbicides, such as phosphinotricin, but are sensitive to HYG at a concentration of 100 mg/l. To our knowledge, no stable transformation has been reported in Arundo, if these experiments are successful, they will represent the first genetic transformation and genetic engineering of Arundo for improving its biomass yield.