Abstract
Sulfur (S) is an essential nutrient for plant growth and development; however, S supply for crop production is decreasing due to reduced inputs from atmospheric deposition and reduced application of S-containing fertilizers. Sulfur deficiency in soil is therefore becoming a widespread cause of reduced grain yield and quality in rice (Oryza sativa L). We therefore assessed the genotypic variation for tolerance to S deficiency in rice and identified loci associated with improved tolerance. Plants were grown in nutrient solution with either low (0.01 mM) or high (1.0 mM) supply of S. Plants grown under low-S treatment showed a reduction in total biomass, mainly due to a marked reduction in shoot biomass, while root biomass and root-to-shoot ratio increased, relative to plants under high-S treatment. Genome-wide association studies (GWAS) identified loci associated with root length (qSUE2-3, qSUE4, and qSUE9), and root (qSUE1, qSUE2-1, and qSUE3-1 and qSUE3-2) or total dry matter (qSUE2, qSUE3-1, and qSUE11). Candidate genes identified at associated loci coded for enzymes involved in secondary S metabolic pathways (sulfotransferases), wherein the sulfated compounds play several roles in plant responses to abiotic stress; cell wall metabolism including wall loosening and modification (carbohydrate hydrolases: beta-glucosidase and beta-gluconase) important for root growth; and cell detoxification (glutathione S-transferase). This study confirmed the existence of genetic variation conferring tolerance to S deficiency among traditional aus rice varieties. The advantageous haplotypes identified could be exploited through marker assisted breeding to improve tolerance to S-deficiency in modern cultivars in order to achieve sustainable crop production and food security.
Highlights
Sulfur (S) is an essential element for growth and development in living organisms; animal digestion, including that of humans, is unable to metabolize sulfur directly
Plants were grown in a modified Yoshida solution where all sources of S were substituted to test the response of a set of rice cultivars to S-deficiency treatments
Plants grown with 1 mM S showed normal growth while those grown in low-S treatment (0.01 mM) showed slow growth and their leaves exhibited the characteristic symptoms of deficiency for this nutrient
Summary
Sulfur (S) is an essential element for growth and development in living organisms; animal digestion, including that of humans, is unable to metabolize sulfur directly. Animals depend on the consumption of plant biomass for the supply of organic S, such as sulfur-containing amino acids (methionine and cysteine), vitamins (thiamine and biotin), and many other secondary compounds (Maruyama-Nakashita et al, 2003; Lunde et al, 2008; Kopriva et al, 2015). Sulfur-containing amino acids are found in very small amounts in legumes, while most cereals contain high levels for example rice (O. sativa L.) contains 190% of the reference value, egg protein (Mariotti, 2017). S is an essential macronutrient needed in similar amounts to Phosphorus for growth and development. Apart from being a vital component of amino acids and vitamins, S is a component of coenzymes, cofactors, lipoic acid, glutathione, sufloquinovosyl diacylglycerol, and many other secondary compounds (Suzuki, 1978; Lunde et al, 2008; Kopriva et al, 2015)
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