Abstract
Wild relatives of wheat, such as Aegilops spp. are potential sources of genes conferring tolerance to drought stress. As drought stress affects seed composition, the main goal of the present study was to determine the effects of drought stress on the content and composition of the grain storage protein (gliadin (Gli), glutenin (Glu), unextractable polymeric proteins (UPP%) and dietary fiber (arabinoxylan, β-glucan) components of hexaploid bread wheat (T. aestivum) lines containing added chromosomes from Ae. biuncialis or Ae. geniculata. Both Aegilops parents have higher contents of protein and β-glucan and higher proportions of water-soluble arabinoxylans (determined as pentosans) than wheat when grown under both well-watered and drought stress conditions. In general, drought stress resulted in increased contents of protein and total pentosans in the addition lines, while the β-glucan content decreased in many of the addition lines. The differences found between the wheat/Aegilops addition lines and wheat parents under well-watered conditions were also manifested under drought stress conditions: Namely, elevated β-glucan content was found in addition lines containing chromosomes 5Ug, 7Ug and 7Mb, while chromosomes 1Ub and 1Mg affected the proportion of polymeric proteins (determined as Glu/Gli and UPP%, respectively) under both well-watered and drought stress conditions. Furthermore, the addition of chromosome 6Mg decreased the WE-pentosan content under both conditions. The grain composition of the Aegilops accessions was more stable under drought stress than that of wheat, and wheat lines with the added Aegilops chromosomes 2Mg and 5Mg also had more stable grain protein and pentosan contents. The negative effects of drought stress on both the physical and compositional properties of wheat were also reduced by the addition of these. These results suggest that the stability of the grain composition could be improved under drought stress conditions by the intraspecific hybridization of wheat with its wild relatives.
Highlights
Drought is one of the most serious stresses affecting crops, and may reduce the yield production of wheat by up to 50% depending on its frequency and duration [1, 2]
The effect of drought on grain composition and quality was studied in wheat/Aegilops addition lines in order to evaluate their usefulness as genetic sources of high quality under drought stress for exploitation in bread wheat
Analysis on a series of wheat/Aegilops addition lines showed that compared to the wheat parents the Aegilops parents had higher protein and β-glucan contents, higher proportions of unsubstituted or less substituted arabinoxylan oligosaccharides (AXOS), and more stable grain composition under drought stress conditions
Summary
Drought is one of the most serious stresses affecting crops, and may reduce the yield production of wheat by up to 50% depending on its frequency and duration [1, 2]. Recent studies have shown that the expression of gliadin and glutenin genes may be affected by drought stress as early as three days after anthesis [9] The amounts of both protein groups are reduced by drought stress, but the magnitude of the effect differs, resulting in decreases in the ratio of glutenins to gliadins and the proportion of unextractable polymeric proteins (UPP%) [7, 10,11,12]. The concentration of GMP was increased by a single early period of drought, a single late period of drought or combined early drought+late heat stress according to Zhang et al [14] These effects could have consequences for processing quality, with Li et al [15] reporting that drought resulted in increased dough strength but reduced bread volume
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