Abstract
Cereal grain fiber is an important health-promoting component in the human diet. One option to improve dietary fiber content and composition in wheat is to introduce genes from its wild relatives Aegilops biuncialis and Aegilops geniculata. This study showed that the addition of chromosomes 2Ug, 4Ug, 5Ug, 7Ug, 2Mg, 5Mg, and 7Mg of Ae. geniculata and 3Ub, 2Mb, 3Mb, and 7Mb of Ae. biuncialis into bread wheat increased the seed protein content. Chromosomes 1Ug and 1Mg increased the proportion of polymeric glutenin proteins, while the addition of chromosomes 1Ub and 6Ub led to its decrease. Both Aegilops species had higher proportions of β-glucan compared to arabinoxylan (AX) than wheat lines, and elevated β-glucan content was also observed in wheat chromosome addition lines 5U, 7U, and 7M. The AX content in wheat was increased by the addition of chromosomes 5Ug, 7Ug, and 1Ub while water-soluble AX was increased by the addition of chromosomes 5U, 5M, and 7M, and to a lesser extent by chromosomes 3, 4, 6Ug, and 2Mb. Chromosomes 5Ug and 7Mb also affected the structure of wheat AX, as shown by the pattern of oligosaccharides released by digestion with endoxylanase. These results will help to map genomic regions responsible for edible fiber content in Aegilops and will contribute to the efficient transfer of wild alleles in introgression breeding programs to obtain wheat varieties with improved health benefits.Key Message: Addition of Aegilops U- and M-genome chromosomes 5 and 7 improves seed protein and fiber content and composition in wheat.
Highlights
Because of its central role in the human diet, wheat is one of the major sources of dietary fiber (DF)
Chinese Spring)/Ae. geniculata (TA2899) chromosome addition lines 1Ug, 2Ug, 3Ug, 4Ug, 5Ug, 6Ug, 7Ug, 1Mg, 2Mg, 3Mg, 5Mg, 6Mg, and 7Mg were kindly provided by Dr Bernd Friebe (Kansas State University, Manhattan, KS, United States) and maintained by the Cereal Genebank, Martonvásár, while a set of bread wheat/Ae. biuncialis (MvGB642) chromosome addition lines 1Ub, 1Ub6Ub, 3Ub, 2Mb, 3Mb, and 7Mb were produced in Martonvásár (Molnár-Láng et al, 2002; Schneider et al, 2005)
No studies have yet been reported on the composition of DF in Aegilops species with the U and M genomes, but previous results on high molecular weight (HMW) glutenin subunit alleles showed wide variation within these species (Ahmadpoor et al, 2014; Dai et al, 2015; Medouri et al, 2015; Wang et al, 2015; Garg et al, 2016)
Summary
Because of its central role in the human diet, wheat is one of the major sources of dietary fiber (DF). The major DF components in wheat grain are the cell wall polysaccharides, arabinoxylan (AX) and (1-3)(1-4)-β-D-glucan (β-glucan), which account for about 70 and 20%, respectively, of the total cell wall polysaccharides in the starchy endosperm (and white flour) (Mares and Stone, 1973). AX and β-glucan occur in soluble and insoluble forms, which may differ in their health benefits. Insoluble DF lowers transit time and increases fecal bulk, defecation frequency, and the binding of carcinogens, while soluble DF reduces the risk of coronary heart disease and type II diabetes. While wheat and rye are rich in AX, barley and oat have high β-glucan content. AX, the main pentosan component of the wheat grain, has a backbone chain of β-Dxylopyranosyl (Xylp) residues linked through (1-4)-glycosidic linkages. The AX in the secondary walls of the pericarp and seed coat tissues of the bran may contain 4-O-methyl α-D-glucuronic acid as an additional substituent at position 2 of Xylp units (Schooneveld-Bergmans et al, 1999)
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