Influence of specific abiotic stress factors on durum wheat gluten proteins and their relation with pasta quality
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Date
2021-01
Authors
Phakela, Keneuoe
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
In recent years, breeding for high quality durum wheat has become an important research focus
due to an increase in demand for good quality products. Wheat storage proteins, termed gluten,
have a major influence on dough quality characteristics, such as visco-elasticity. The gluten proteins are strongly influenced by genotype, environment and genotype by environment interaction. This may consequently cause variation in quality. Limited information is available on the impact of genotype, environment and their interaction on durum wheat gluten proteins. Most research has focused on the effects of environmental conditions on bread wheat quality. In order to improve durum wheat quality, it is important to understand the impact of environmental conditions on durum wheat gluten proteins. In this study, six durum wheat cultivars were planted in Mexico under six environmental conditions: optimum, flood irrigation, moderate heat, severe heat, moderate drought and severe drought. The aim of this study was to determine the effect of heat and drought stress on protein quantity and quality, using size exclusion-high performance liquid chromatography (SE-HPLC), reversed phase-high performance liquid chromatography (RPHPLC) and proteomics techniques. Flour protein content was significantly increased by all stress treatments. High flour protein content was observed under severe heat and drought stress
conditions. There were significant differences between genotypes for protein fractions separated
by SE-HPLC. All stress treatments caused a significant reduction in extractable and unextractable albumin/globulin protein fractions, as well as in extractable and unextractable low molecular weight (LMW) gluten proteins. Severe drought stress caused an increase in large SDSunextractable polymeric proteins. Moderate and severe heat stress significantly increased SDSextractable gliadin. Genotype effect was large for extractable LMW for all environments except for severe drought. The SDS-unextractable LMW correlated significantly with alveograph strength (alvW) and mixograph peak time (MPT). RP-HPLC indicated a significant reduction in LMW glutenins and γ-gliadin, and an increase in α- gliadins for all stress treatments. Genotype affected α-gliadins more than environment and genotype by environment interaction, indicating a strong genetic influence on the expression of these gliadins. The γ-gliadins showed positive significant correlations with alvW, alvP and MPT for most treatments. The ω- and α-gliadins had a negative relationship with alveograph parameters. Proteomic analysis revealed 330 protein spots differentially expressed in cultivar AtilC2000, with the largest number of spots (14.24%) up-regulated by all stress conditions. In Mexicali75, 205 spots were differentially expressed and most protein spots (35.12%) increased due to moderate drought stress conditions. Highly up-regulated protein spots were analysed by liquid chromatography tandem mass spectrometry (LC-MS/MS) followed by database searching. Of these, some were HMW-GS, gliadins, serpins, and β-amylase involved in carbohydrate metabolism. Drought and heat significantly altered the gluten protein composition, by upregulating HMW and gliadin proteins in the two cultivars. Generally, cultivars differed in terms of their reaction to stress conditions. This suggests that the effects of stress cannot be generalised in durum wheat.
Description
Keywords
Thesis (Ph.D. (Plant Sciences (Plant Breeding))--University of the Free State, 2021, Abiotic stress, Durum wheat quality, Glutenin, Size exclusion-high performance liquidnchromatography, Reversed phase-performance liquid chromatography, Proteomics