Abstract
Predictions of future climate scenarios indicate that yields from perennial biomass crops (PBCs) growing in the Mediterranean region are likely to decline due to prolonged drought. Among PBCs, Miscanthus grasses with C4 photosynthesis combine high yield potentials and water use efficiencies. However, the standard commercial clone M. x giganteus (Mxg), with minimal stomatal regulation, is too sensitive to drought for reliable yields in the Mediterranean regions. This paper screened a diverse panel of thirteen Miscanthus genotypes (M. sinensis, M. floridulus, M. sacchariflorus and Mxg) to identify which types could maximize yield under summer drought conditions typical in the South Mediterranean climate. In the second growing season, significant differences were observed for plant height (from 63 to 185 cm), stem number (from 12 to 208 stems plant−1), biomass yield (from 0.17 to 6.4 kg DM plant−1) and whole crop water use efficiency (from 0.11 to 7.0 g L−1). Temporal variation in net photosynthesis, stomatal conductance, transpiration rate and instantaneous water use efficiency identified different strategies adopted by genotypes, and that genotypes selected from M. floridulus and M. sinensis were better adapted to rainfed conditions and could produce six times more biomass than the Mxg. These accessions are being used as parents in experimental breeding aimed at producing future seed-based drought resilient hybrids.
Highlights
Growing biomass crops on marginal lands has been proposed as a feasible solution to reduce pressure on higher-grade lands and to reduce competition with food crops [1]
This study increased our knowledge of different mechanistic responses to drought for development of genotypes that are more resilient to climate change and for sustainable development of biomass crops for the bioeconomy
The study was conducted only for one growing season, information on the physiology, morphology and yield of wild Miscanthus germplasm grown under irrigation and prolonged water stress conditions in the field significantly contributes toward our ability to select appropriate genotypes expressing useful variation in target traits for crossing to produce novel drought-tolerant plants
Summary
Growing biomass crops on marginal lands has been proposed as a feasible solution to reduce pressure on higher-grade lands and to reduce competition with food crops [1]. It is expected that perennial biomass crops (PBCs) will make a substantial contribution to renewable low carbon energy systems and in combination with bio-energy with carbon capture and storage (BECCS) will produce carbon-negative energy [6]. Among PBCs, a large effort in Europe has been focused on Miscanthus, mainly due to its wide geographical adaptability, C4 photosynthetic metabolism and high biomass output to Agronomy 2020, 10, 679; doi:10.3390/agronomy10050679 www.mdpi.com/journal/agronomy. Despite the large genetic diversity of this genus, the most widely used Miscanthus for biomass production is M. x giganteus, a naturally occurring triploid hybrid [7,13,14]. M. x giganteus is sterile commercial expansion is limited by low multiplication rates from clonal propagation, high establishment costs and patchiness associated with rhizome propagation [15,16]. The physiology of M. x giganteus is not well suited to areas with limited water supply and extreme summer drought, such as the southern Mediterranean [17,18]
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