## 1 Introduction  
Soil salinity is a major environmental factor that limits growth and development of plants and reduces the height and quality of crops, especially in arid and semi-arid regions [1]. The area of naturally saline soils in the world is estimated to be about 1 billion ha, while secondary salimization occurs in 77 million ha. As a result of physiological drought (too high osmotic potential of the soil solution), salt stress causes a water deficiency in plant tissues. It inhibits seed germination and seedling growth, as well as reduces the length of roots and shoots [2]. Lignocellulosic bioenergy crops in marginal habitats, including salt-affected soils, can be an interesting alternative to traditionally cultivated plants. These include tall fescue (_Festuca arundinacea_ Schreb., Poaceae), a cool-season C3 perennial, pasture and turf grass growing up to 70-120 cm in height, with large, dense and deeply rooted clumps. It occurs naturally throughout Europe (north to 62\({}^{\circ}\) in Scandinavia), in North Africa and Western and Central Asia [3]. _F. arundinacea_ grows on moist meadows, pastures, levees, riverbanks, salt marshes, seashores and cliffs. It is recorded on several types of substrates, usually on poorly drained, alluvial soils [3]. This is a stress-tolerant species with a tendency of apophytism, encroaching on anthropogenic habitats such as roadsides, railway embankments, wastelands, etc. _F. arundinacea_ is a quickly growing plant distinguished by its large biomass production and broad ecological scale, including high tolerance to abiotic stress, waterlogging, salinity, drought and low temperature [4; 5; 6; 7]. In the case of oxygen deficit in the root zone, tall rescue shows the ability to form aerenchyma [8]. This species has also developed both metabolic and physiological mechanisms to counteract drought such as leaf rolling and a rapid stomatal closure [9]. Thanks to a strong root system, it can take water from the soil from a depth of more than 1 m [3]. Literature data have indicated the usefulness of this species in phytoremediation of soils contaminated with heavy metals: lead, cadmium, copper, zinc and nickel [10; 11]. These biological features make tall rescue a model plant in research concerning molecular mechanisms of grass tolerance to abiotic stress [12]. Due to low rainfall, high evaporation, salt-water irrigation, overfertilization and other factors, saline areas are increasing by about 10% per year, and we conducted preliminary research on the use of haplotypes in the development of an integrated system for bioremediation of saline soils and biorefinery of their biomass [1; 13]. Halophyte biomass contains a lignocellulosic complex, which is relatively resistant to biodegradation. Biofuel production from plant biomass requires degrading cell walls to specific polymers and hydrolysis of carbohydrates to monomer sugars. It includes the plant material preparation (physico-chemical pretreatment), enzymatic hydrolysis up to alcoholic fermentation [14]. Pretreatment of plant biomass generally allows for loosening of the compact structure of lignocellulosic, including increasing the internal surface of the cellulose, reducing the degree of polymerization and crystallinity, and delignification of the raw material [15; 16]. Next, an effective and economical solution for further processing of biomass into ethanol seems to be the SSF process, which combines cellulose hydrolysis with fermentation of sugars in one bioreactor, and the enzymes must be adapted to the fermentation temperature of the process of 30-40 \({}^{\circ}\)C (optimal temperature for distillery yeast _Saccharomyces cerevisiae_) [17; 18; 19]. The use of tall rescue biomass from saline soils is certainly important due to the EU Directive on Renewable Energy Sources 2018/2021 (RED II) defining the criteria for the sustainable development of biofuels, including biofuels from plant biomass, whose share in the transport sector by 2030 should amount to 3.5% [20].