Wild biomass perennial grasses show tolerance to dry conditions in a Mediterranean climate

The productivity of biomass perennial grasses (BPGs) in the marginal areas of the Mediterranean is mainly limited by water scarcity. To address this constraint, this study investigated the impact of different irrigation levels on the morphological and productive traits of seven BPG genotypes belonging to Arundo donax L., Saccharum spontaneum, and Miscanthus hybrids, adopting a split-plot experimental design under the Mediterranean climatic conditions of Sicily (Italy) during a three-year experiment. Results showed that water availability significantly affects biomass yield, particularly during early crop development, with all genotypes benefiting from irrigation through increased stem and leaf biomass. However, notable differences emerged among species: while Arundo donax and Saccharum spontaneum exhibited strong drought tolerance, maintaining stable aboveground biomass and stem density without irrigation, Miscanthus × giganteus was more susceptible to water stress, showing marked biomass declines under rainfed conditions. Conversely, Miscanthus hybrids GNT3 and GNT43, bred for drought tolerance, outperformed S. spontaneum under rainfed environments and achieved biomass yields comparable to A. donax when irrigated. Notably, despite biomass reduction under drought conditions, the chemical composition of the biomass (lignin, cellulose, hemicellulose, and ash) remained stable, indicating that biomass quality was not adversely affected by water stress. These findings confirm the role of effective water management and genotype selection for optimizing biomass yield and resource efficiency, providing valuable insights for enhancing crop productivity in Mediterranean and other semi-arid regions. The evaluated species represent promising candidates for cultivation under water scarcity due to their high water use efficiency and tolerance to water stress.