Wheat stem reserves and salinity tolerance: molecular dissection of fructan biosynthesis and remobilization to grains.

Fructan accumulation and remobilization to grains under salinity can decrease dependency of the wheat tolerant cultivar on current photosynthesis and protect it from severe yield loss under salt stress. Tolerance of plants to abiotic stresses can be enhanced by accumulation of soluble sugars, such as fructan. The current research sheds light on the role of stem fructan remobilization on yield of bread wheat under salt stress conditions. Fructan accumulation and remobilization as well as relative expression of the major genes of fructan metabolism were investigated in the penultimate internodes of 'Bam' as the salt-tolerant and 'Ghods' as the salt-sensitive wheat cultivars under salt-stressed and controlled conditions and their correlations were analyzed. More fructan production and higher efficiency of fructan remobilization was detected in Bam cultivar under salinity. Up-regulation of sucrose: sucrose 1-fructosyltransferase (1-SST) and sucrose: fructan 6-fructosyltransferase (6-SFT) (fructan biosynthesis genes) at anthesis and up-regulation of fructan exohydrolase (1-FEH) and vacuolar invertase (IVR) genes (contributed to fructan metabolism) during grain filling stage and higher expression of sucrose transporter gene (SUT1) in Bam was in accordance with its induced fructan accumulation and remobilization under salt stress. A significant correlation was observed between weight density, WSCs and gene expression changes under salt stress. Based on the these results, increased fructan production and induced stem reserves remobilization under salinity can decrease dependency of the wheat tolerant cultivar on current photosynthesis and protect it from severe yield loss under salt stress conditions.