Abstract
Miscanthus is a woody rhizomatous C4 grass that can be used as a CO2 neutral biofuel resource. It has potential to grow in marginal areas such as saline soils, avoiding competition for arable lands with food crops. This study explored genetic diversity for salt tolerance in Miscanthus and discovered mechanisms and traits that can be used to improve the yield under salt stress. Seventy genotypes of Miscanthus (including 57 M. sinensis, 5 M. sacchariflorus, and 8 hybrids) were evaluated for salt tolerance under saline (150 mM NaCl) and normal growing conditions using a hydroponic system. Analyses of shoot growth traits and ion concentrations revealed the existence of large variation for salt tolerance in the genotypes. We identified genotypes with potential for high biomass production both under control and saline conditions that may be utilized for growth under marginal, saline conditions. Several relatively salt tolerant genotypes had clearly lower Na+ concentrations and showed relatively high K+/Na+ ratios in the shoots under salt stress, indicating that a Na+ exclusion mechanism was utilized to prevent Na+ accumulation in the leaves. Other genotypes showed limited reduction in leaf expansion and growth rate under saline conditions, which may be indicative of osmotic stress tolerance. The genotypes demonstrating potentially different salt tolerance mechanisms can serve as starting material for breeding programs aimed at improving salinity tolerance of Miscanthus.
Highlights
Miscanthus is a C4 perennial grass originating from Southeast Asia, the Pacific islands, and tropical Africa
The results showed that several genotypes with relatively high salt tolerance appeared to rely on different mechanisms, offering opportunities for breeding programs aimed at improved tolerance of Miscanthus
Two genotypes (OPM-13 and OPM-38) were grown on hydroponics at three different salt conditions (0, 125, and 250 mM NaCl). Growth of these Miscanthus genotypes was already affected at 125 mM (Shoot Dry Weight was reduced by 24 and 68% for OPM-38 and OPM-13, respectively, and 36 and 63% at 250 mM NaCl)
Summary
Miscanthus is a C4 perennial grass originating from Southeast Asia, the Pacific islands, and tropical Africa. The genus Miscanthus has a basic chromosome number of 19, and includes the nominally diploid species Miscanthus sinensis (2N = 2x = 38) and tetraploid species Miscanthus sacchariflorus (2N = 4x = 76) plus a triploid interspecific hybrid, Miscanthus × giganteus (3n = 3x = 57). This hybrid was identified as a good candidate for energy production by direct combustion (Zub and Brancourt-Hulmel, 2010). Since Miscanthus × giganteus is a sterile triploid, it is difficult to improve its genetics by crossing. An important breeding goal for any bioenergy crop and Miscanthus is to achieve economically viable yields in marginal lands, avoiding competition with food crops and interfering with food security (Somerville et al, 2010)
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