Assessing salt-stress tolerance in barley

Univ. Sci. 24 (1): 91-109, 2019. doi: 10.11144/Javeriana.SC24-1.asst Bogotá original article Assessing salt-stress tolerance in barley Somasundaram Rajeswari1, *, Neeru Sood, Trupti Gokhale Swarup, Ramachandran Subramanian Edited by Juan Carlos Salcedo-Reyes () 1. Birla In itute of Technology and Sciences, Pilani, Department of Biotechnology, Dubai Campus. * Received: 23-01-2018 Accepted: 13-9-2018 Published on line: 04-03-2019 Citation: Rajeswari S, Sood N, Gokhale ST, Subramanian R. Assessing salt-stress tolerance in barley, Universitas Scientiarum, 24 (1): 91-109, 2019. doi: 10.11144/Javeriana.SC24-1.asst Funding: N.A. Electronic supplementary material: Supp. 1. Abstract Identifying naturally existing abiotic-stress tolerant accessions in cereal crops is central to understanding plant responses towards stress. Salinity is an abiotic stressor that limits crop yields. Salt stress triggers major physiological changes in plants, but individual plants may perform differently under salt stress. In the present study, 112 barley accessions were grown under controlled salt stress conditions (1 Sm−1 salinity) until harvest. The accessions were then analyzed for set of agronomic and physiological traits. Under salt stress, less than 5 % of the assessed accessions (CIHO6969, PI63926, PI295960, and PI531867) displayed early flowering. Only two (< 2 %) of the accessions (PI327671 and PI383011) attained higher fresh and dry weight, and a better yield under salt stress. Higher K+ /Na+ ratios were maintained by four accessions PI531999, PI356780, PI452343, and PI532041. These top-performing accessions constitute naturally existing variants within barley’s gene pool that will be instrumental to deepen our understanding of abiotic-stress tolerance in crops. Keywords: Agronomic trait; barley; salt stress; yield parameters Introduction Salinity affects crops worldwide. In arid and semi-arid environments, salinity’s negative effects on crops are exacerbated by high temperature and inadequate water supply. FAO estimated that approximately 20 % of the world’s agricultural land is saline [1]. Further, inadequate agricultural practices lead to salinization of approximately 2 000 hectares of land in arid and semi-arid areas per day [2]. Salinity alters a plant’s water and mineral nutrient (osmotic and ionic) balance, and prolonged exposure to salinity leads to changes in the molecular and biochemical mechanisms controlling plant development, growth and reproduction [3]. Salinity-induced changes Universitas Scientiarum, Journal of the Faculty of Sciences, Pontificia Universidad Javeriana, is licensed under the Creative Commons Attribution 4.0 International Public License 92 Salt-stress in barley in plants, are modulated by changes in gene expression [4]. Facing an unrelenting salinization of agricultural land, the best way to increase crop production is by planting salt-tolerant and high yielding accessions [5, 6]. To this end, we must first identify, by reliable screening procedures, naturally existing salt-tolerant accessions in crop gene pools. Barley (Hordeum vulgare) is the most salt tolerant cereal crop [7], and it is the fourth most important cereal crop grown worldwide due to its nutritional and health benefits [8]. Barley is also a model crop because of its agronomic, molecular and genetic diversity, which has been exploited and developed since ancient times [9]. Barley is copious in genetic diversity entailed in many landraces and progenitor species. Thus, barley exhibits variation for traits of agricultural importance, such as high yield, resistance to infections, tolerance to abiotic stressors like drought, salt, cold etc. As environmental conditions become more limiting for agriculture, the natural adaptability of cereal crops, like barley ought to be constantly assessed. In the present study, the agronomic, biochemical and yield attributes of 112 barley accessions obtained from USDA were evaluated for salt stress tolerance under field condition in Dubai to find the salt tolerant accessions. Materials and methods Controlled salt stress experiments were carried out in the field at BITS Pilani, Dubai Campus (25.2048◦ latitude north, 55.2708◦ east) in the United Arab Emirates. Dubai is classified as an arid environment. The study was conducted during the 2015-16 winter season (Nov-Feb). The experimental growth field, of size 120 m, was prepared to maintain suitable conditions for efficient irrigation and to get maximum sunlight for plant growth. The field was leveled by plowing and removal of large stones. Since, desert soil is not suitable for plant growth because of its very high sand and salt concentration (106 mM) with electrical conductivity (ECe) of 1 056 and a negligible amount of organic matter. Hence a new layer of commercial sweet soil (0.5 m deep) was laid over the sand. This prevents plant roots from directly contacting the underlying highly saline desert soil during the trial. Sweet soil’s pH and ECe were determined using saturated paste extract [10] and they were 7.2 and 0.045 Sm−1 , respectively. The field was irrigated with fresh water (0.003 Sm−1 ) for three days to keep it moist before planting. Grass was grown around the trail field to buffer edge effects. An experiment was carried out on a complete randomized block design with five replicates. A total of 112 barley accession obtained from the United States Department of Agriculture (USDA) were assessed in this study. Barley accessions Universitas Scientiarum Vol. 24 (1): 91-109 http://ciencias.javeriana.edu.co/investigacion/universitas-scientiarum 93 Somasundaram et al. 2019 originated from Africa (Algeria, Egypt, Ethiopia, and Morocco); America (Canada, Peru, and the USA); Asia (Bhutan, China, India, Israel, Japan, Nepal, Saudi Arabia, Pakistan, the Russian Federation, and Syria); Europe (Croatia, England, Germany, Hungary, Norway, Sweden, and Ukraine); and Oceania (Australia). The accessions comprised an array of agronomic categories, such as cultivars, genetic material, breeding material, landraces, and untested results of selection endeavors (henceforth referred to as uncertain improvement). All the accessions were further classified by row type (two-row or six-row or irregular), caryopsis type (covered or hull-less), and growth habit (spring or winter or facultative; Table 1). Seeds of each accession were disinfected with 6 % hydrogen peroxide and rinsed with distilled water. Sterilized seeds were germinated on moist petri plates at room temperature. Radicle emergence was considered as a sign of germination. Subsequently seedlings were planted in the prepared field. Each accession was planted in a separate raised garden bed of length 0.44 m and breadth 0.1 m. All beds were spaced 0.3 m apart. Seedlings were irrigated with fresh water (ECe 0.003 Sm−1 ) twice a day until they reached their 3-leaf stage. One liter of freshwater was mixed with 5.8 g of sodium chloride to make 100 mM, 1 Sm−1 , sa (...truncated)