Physical Mutagenesis in Giant Reed (Arundo Donax L.) and Phenotypic and Genomic Characterization of Mutagenized Clones

ABSTRACT Giant reed (Arundo donaxL.) is a C3 perennial, warm-season, rhizomatous grass of emerging interest for bioenergy and biomass-derivatives production, and for phytoremediation. We developed and applied a mutagenesis protocol based on γ-irradiation of in-vitro cell cultures from which regenerants were obtained. Based on a radio-sensitivity test, the irradiation dose reducing to 50% the number of regenerants per callus (RD50) was estimated at 35 Gy. A large mutagenic experiment was carried out by irradiating a total of 3,120 calli with approx. 1x, 1.5x and 2x RD50. A total of 1,004 regenerants from irradiated calli were hardened in pots and transplanted to the field. Approx. 10% of field grown clones showed remarkable morphological aberrations including dwarfism, altered tillering, abnormal inflorescence, leaf variegation and others, which were tested for stability over generations. Clone lethality reached 0.4%. Our results show for the first time that physical mutagenesis can efficiently induce new genetic and phenotypic variation of agronomic and prospective industrial value in giant reed. 100 clones of A. donax were chemically analyzed for several key chemical components of plant biomass including lignin, cellulose, hemicelluloses, non-structural carbohydrates, ash, and others. The complete chloroplast genome of A. donax is 139353 bp in length subdivide in two inverted repeat region (IRa and IRb) of 22,227 bp each separated by a small-single-copy-region of of 12,275 bp (SSC) and a large-single-copy-region of 82,124 bp (LSC). The genome includes 112 individual genes including 72 protein coding genes, 30 tRNA, 6 rRNA, 3 open reading frames and one pseudogene. FISH ang GISH analysis were performed on three species A. donax, A. plinii and P. australis in order to define the genetic structure of these species and the phylogenetic relationship existing among them.