Abstract
Background and AimsWater deficit and salinity stresses are often experienced by plants concurrently; however, knowledge is limited about the effects of combined salinity and water deficit stress in plants, and especially in C4 bioenergy crops. Here we aim to understand how diverse drought tolerance traits may deliver tolerance to combinations of drought and salinity in C4 crops, and identify key traits that influence the productivity and biomass composition of novel Miscanthus genotypes under such conditions.MethodsNovel genotypes used included M. sinensis and M. floridulus species, pre-screened for different drought responses, plus the commercial accession Miscanthus × giganteus (M×g.). Plants were grown under control treatments, single stress or combinations of water deficit and moderate salinity stress. Morphophysiological responses, including growth, yield, gas exchange and leaf water relations and contents of proline, soluble sugars, ash and lignin were tested for significant genotypic and treatment effects.Key ResultsThe results indicated that plants subjected to combined stresses showed more severe responses compared with single stresses. All novel drought-tolerant genotypes and M×g. were tolerant to moderate salinity stress. Biomass production in M. sinensis genotypes was more resilient to co-occurring stresses than that in M×g. and M. floridulus, which, despite the yield penalty produced more biomass overall. A stay-green M. sinensis genotype adopted a conservative growth strategy with few significant treatment effects. Proline biosynthesis was species-specific and was triggered by salinity and co-occurring stress treatments, mainly in M. floridulus. The ash content was compartmentalized differently in leaves and stems in the novel genotypes, indicating different mechanisms of ion accumulation.ConclusionsThis study highlights the potential to select novel drought-tolerant Miscanthus genotypes that are resilient to combinations of stress and is expected to contribute to a deeper fundamental knowledge of different mechanistic responses identified for further exploitation in developing resilient Miscanthus crops.
Highlights
The area of arid and saline land is increasing and is expected to have a major impact on future crop productivity
There was a genotypic difference in accumulated above-ground biomass when plants were grown in well-watered (C) treatments, with the highest levels in M. × giganteus and M. floridulus genotypes; M. sin. 1 accumulated intermediate levels and M. sin. 2 the lowest
Above-ground biomass accumulated to lower levels in S and S+D treatments compared with C and D treatments in all genotypes, but these reductions were not significant in the M. sinensis genotypes
Summary
The area of arid and saline land is increasing and is expected to have a major impact on future crop productivity. The environmental stresses resulting from climate change and unsustainable irrigation practices are predicted to impact crop productivity and reduce the area of available land for agriculture by 2–9 % globally and by 11–17 % within Europe (Zhang and Cai, 2011). Since irrigation of biomass crops is unlikely to be economic, it is important to identify genotypes that optimize the use of water in different climatic regions and those that are tolerant to salinity and water-deficit stresses. Plants are usually subjected to combinations of stresses, such as water deficit and salinity, concurrently throughout the growing season (Suzuki et al, 2014; Pandey et al, 2017). Physiological responses to drought include control of stomatal aperture, decreased photosynthetic activity, altered cell-wall elasticity and the generation of toxic metabolites causing plant cell death (Ahuja et al 2010), whereas under prolonged salinity, in addition to water deficits, plants are subjected to further stress due by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited
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