Novel Miscanthus genotypes selected for different drought tolerance phenotypes show enhanced tolerance across combinations of salinity and drought treatments

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.

Morphological and Physiological Traits that Explain Yield Response to Drought Stress in Miscanthus

“…However, for all plants trajectories of stem growth, leaf expansion, and tillering (stem number) curves were significantly affected by the applied treatment. Several studies, both in greenhouse and field conditions, reported that stem elongation and leaf area were significantly affected in M. × giganteus and M. sacchariflorus but not in M. sinensis [17,[25][26][27]29,34,57]. In the present study, the morphological trait changes under applied drought conditions were in line with previous findings for pots experiments [25,28,29,34,58].…”

“…To test this, a large number of phenotypic traits associated with yield accumulation [17][18][19][20], and complex traits such as seasonal duration and harvestable yield [21][22][23] have been measured in diverse miscanthus populations. A number of studies have examined responses to, and genotypic variation in traits associated with, drought [24][25][26][27][28][29]. However, drought resistance in undomesticated miscanthus is the result of natural evolution and may not necessarily favour growth under stress but rather survival.…”

Physiological Response of Miscanthus x giganteus to Plant Growth Regulators in Nutritionally Poor Soil

“…Different miscanthus species vary in tolerance to various physical factors. According to physiological measurements (F v /F m ), Mxg displayed the highest vitality under cold (together with M. sacchariflorus) [15] and drought (together with M. sinensis) [16] stress among other miscanthus species. Mxg physiological response was more sensitive to salinity and combination of salinity and drought than M. sinensis but more tolerant than M. floridulus [16].…”

“…According to physiological measurements (F v /F m ), Mxg displayed the highest vitality under cold (together with M. sacchariflorus) [15] and drought (together with M. sinensis) [16] stress among other miscanthus species. Mxg physiological response was more sensitive to salinity and combination of salinity and drought than M. sinensis but more tolerant than M. floridulus [16]. Also novel hybrids were developed, which exhibited higher yields under drought, salinity and cold stress conditions than Mxg [17].…”

The Effects of Moderate and Severe Salinity on Composition and Physiology in the Biomass Crop Miscanthus × giganteus

“…Miscanthus sinensis exhibits salt spray tolerance growing in coastal landscapes as ornamental grass [ 5 , 6 ], with salt concentrations higher than 10 dS m −1 NaCl reducing the yield by over 50% [ 7 ]. The genetic diversity of salt tolerance to combinations of salinity and drought conditions [ 8 ] and single salt stress in Miscanthus have been recently documented [ 9 , 10 , 11 ]. Nevertheless, studies of salt tolerance mechanisms in Miscanthus have focused on the morphophysiological and biochemical [ 7 , 8 , 10 , 11 , 12 , 13 ] and transcriptional [ 14 ] responses.…”