Greener Journal of Agricultural Sciences

ISSN: 2276-7770; ICV: 6.15

Vol. 6 (8), pp. 252-255, September 2016

Copyright ©2017, the copyright of this article is retained by the author(s)

http://gjournals.org/GJAS

 

 

 

 

Research Article (DOI: http://doi.org/10.15580/GJAS.2016.8.082416138)

 

Variation in High Molecular Weight Glutenin Subunits and Seed Chemical Contents in Ethiopian Bread Wheat (Triticum aestivum L.) Varieties

 

 

Alemayehu Balcha

 

 

Hawassa Agricultural Research Centre, Southern Agricultural Research Institute, POB 2126, Hawassa, Ethiopia.

 

 

ARTICLE INFO

ABSTRACT

 

Article No.: 082416138

DOI: 10.15580/GJAS.2016.8.082416138

 

High molecular weight glutenin subunits largely determine bread making quality of wheat. A study was done from April to May, 2015, in the Division of Plant Breeding, Department of Crop Sciences, University of Natural Resources and Life Sciences, Vienna, Austria, using seventeen bread wheat varieties of Ethiopia in order to determine high molecular weight glutenin subunits and seed chemical contents. Ash content ranged from 2.24 (variety Warrakatta/Pastor) to 3.44% (variety Mekelle-3), fat 2.73 (variety Alidoro) to 3.57% (variety Hulluka), starch 63.69 (variety Tay) to 70.98% (variety Alidoro), protein 14.00 (variety Mekelle-3) to 16.75% (variety Tay), gluten 32.96 (variety Mekelle-3) to 38.66% (variety Tay), and 1000-seed weight 24.30 (variety Jefferson) to 35.77(g) (variety Hidase). SDS-PAGE analysis showed that loci Glu-A1, Glu-B1 and Glu-D1 consisted of three, five and two subunits, respectively. Varieties ETBW5879, Worrakatta/Pastor, Hulluka, Mekelle-3, Kakaba, Danda´a, Alidoro, Pavon-76 and Jefferson consisted of subunits 1 or 2*, 7+8 or 17+18, and 5+10 at Glu-A1, Glu-B1 and Glu-D1 loci, respectively, and Glu-1 quality score of ten. Variety Tay consisted of subunits null, 6+8 and 2+12 at Glu-A1, Glu-B1 and Glu-D1, respectively, and Glu-1 quality score of four. The present study suggests that varieties combing 1 or 2*, 7+8 or 17+18, and 5+10 subunits at Glu-A1, Glu-B1 and Glu-D1, respectively, would be used to improve bread making quality of wheat in the future breeding programs.

 

 

Submitted: 24/08/2016

Accepted: 30/08/2016

Published: 29/09/2016

 

*Corresponding Author

Alemayehu Balcha

E-mail: albalcha@ yahoo.com

 

 

Keywords:

Bread wheat,  glutenin, protein, gluten, Triticum aestivum

 

 

 

 

 

 

INTRODUCTION

 

Wheat protein (8 to 20% of the grain) mainly contains albumins, globulins, gliadins and glutenins. Glutenin protein is a polymer of long chain of polypeptide subunits linked by inter polypeptide disulfide bonds. The reduction of these inter-chain bonds allows the separation of the subunits into high molecular weight (HMW) (80-130 kDa) and low molecular weight (LMW) (10-70 kDa) glutenin subunits (Bietz and Wall, 1972).The former constitutes about 5 to 10% and that of the later about 20 to 30% of the total grain protein (Eagles et al., 2002). The HMW glutenin subunits are encoded by two types of genes (x:y)  that are located at Glu-Al, Glu-Bl and Glu-Dl loci close to centromere on the long arm of the homologous chromosomes lA, 1B and lD, respective1y (Payne et al., 1982). The x-gene encodes for high molecular weight x-type subunit, whereas y-gene encodes for LMW y-type subunit (Shewry et al., 1992).

Bread wheat is expected to contain six different HMW glutenin subunits but due to silencing of some of these genes(x,y), most bread wheat cultivars possess three to five subunits. Thus, Glu-A1 locus encodes for none or one active subunit (y-type of this locus is not expressed) and loci Glu-B1 and Glu-D1 encode for one or two x-type subunits each (Payne and Lawrence, 1983). On the other hand, genes encoding for LMW glutenin subunits are located on the short arms of homologous group 1 chromosomes at Glu-A3, Glu-B3 and Glu-D3 loci, and are tightly linked to Glu-1 loci (Liu et al., 2010). Moreover, the presence or absence of specific HMW glutenin subunits largely determines bread making quality of wheat. In general, subunits null, 6+8, and 2+12 at Glu-A1, Glu-B1 and Glu-D1, respectively, are negatively related to break making quality (Payne et al., 1987; Weegels et al., 1996). The present study was done to determine high molecular weight glutenin subunits and seed chemical contents for seventeen Ethiopian bread wheat varieties.

 

 

MATERIALS AND METHODS

 

This study was done in the Division of Plant Breeding, Department of Crop Sciences, University of Natural Resources and Life Sciences, Vienna, Austria, from April to May, 2015, using seed samples of seventeen wheat varieties grown at Halaba experimental station (7o18’45”N, 38o06’49”E and 1765 m above sea level) of Hawassa Agricultural Research Centre, Hawassa, Ethiopia, from August to November, 2014, during main cropping season. Seed samples were analyzed for ash, fiber and starch contents using near-infrared reflectance spectroscopy (NIRS) (Buker, Ettlingen, Germany), and protein and gluten contents using NIR spectrometer, NIRFlex N-500 (BÜCHI, Labortechnik AG, Flawi, Switzerland). Seven seeds were sampled for each variety and ground into fine powder for the determination of HMW glutenin subunits using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with 10% polyacrylamide gels as it was described by Payne et al. (1980). The numbering of glutenin subunits and calculation of Glu-1 quality score were done according to Payne and Lawrence (1983) and Payne et al. (1987), respectively.

 

 

RESULTS

 

Ash content ranged from 2.24 (variety Warrakatta/Pastor) to 3.44% (variety Mekelle-3), fat 2.73 (variety Alidoro) to 3.57% (variety Hulluka), starch 63.69 (variety Tay) to 70.98% (variety Alidoro), protein 14.00 (variety Mekelle-3) to 16.75% (variety Tay), gluten 32.96 (variety Mekelle-3) to 38.66% (variety Tay), and 1000-seed weight 24.30 (variety Jefferson) to 35.77(g) (variety Hidase) (Table 1).

 

 

 

For the seventeen bread wheat varieties, SDS-PAGE analysis gave HMW glutenin subunits of three, five and two at Glu-A1, Glu-B1 and Glu-D1 loci, respectively. Out of the seventeen varieties, nine of them combined 1 or 2*, 7+8 or 17+18, and 5+10 subunits at Glu-A1, Glu-B1 and Glu-D1, respectively, and had Glu-1 quality scores of  ten .  On  the other hand, variety Tay consisted of null, 6+8 and 2+12 subunits at Glu-A1, Glu-B1 and Glu-D1, respectively, and had the lowest Glu-1 quality scores of four (Table 2).

 

 

 

DISCUSSION 

 

As to the present study, the presence of HMW glutenin subunits of null, 1 and 2* at Glu-A1 has been reported in previous studies in bread wheat (Payne and Lawrence, 1983; Payne et al., 1987; Lukaw et al., 1989; Nakamura, 2000; Anwar et al., 2003; Chaparzadeh et al., 2008; Giraldo et al., 2010) despite that Giraldo et al., (2010) have also reported the presence of 2** glutenin subunit. In the present study, the number of alleles obtained at Glu-B1 was similar to that reported in previous studies (Payne et al., 1987; Galova et al., 2002; Anwar et al., 2003; Chaparzadeh et al., 2008) except that seven (Lukow 1989; Giraldo et al., 2010) and 11(Nakamura, 2000) alleles have been reported by other studies. Even though there were two alleles observed in the present study at Glu-D1, three (Galova et al., 2002; Giraldo et al., 2010), four (Payne et al., 1987; Lukow et al., 1989), five (Anwar et al., 2003) and six (Nakamura, 2000) alleles have been reported at this locus. Varieties having subunits 1 or 2*,  7 + 8 or 17 + 18, and  5+10 at Glu-A1, Glu-B1 and Glu-D1, respectively, are expected to have high sedimentation and mixing time values which give high stability, elasticity and mixing tolerance to the dough compared to other subunits on the same locus (Giraldo et al., 2010).

In the present study, some varieties having 1 or 2* subunits at Glu-A1 had reduced Glu-1 quality scores attributed to 7+9 subunit at Glu-B1 locus. The highest value of Glu-1 quality score of ten was achieved for nine of the seventeen varieties studied indicating that these varieties could be expected for their good bread making qualities (Payne et al., 1987; Galova et al., 2002).  However, variety Tay could be judged as weak quality genotype because of its null, 6+8 and 2+12 subunits giving it lowest Glu-1 quality score of four. On the other hand, high positive correlation between protein and gluten contents (r=0.97, p<0.01) observed in the present study could be expected because gluten represents 75 to 85% of the grain protein content (Abdel-Aal et al., 1996; Belderok et al., 2000). The present study suggests that varieties combing 1 or 2*, 7+8 or 17+18, and 5+10 subunits at Glu-A1, Glu-B1 and Glu-D1, respectively, would be used to improve bread making quality of wheat in the future breeding programs.

 

 

ACKNOWLEDGMENTS

 

The author thanks Austrian Agency for International Cooperation in Education and Research (OEAD) for the scholarship grant provided for this study, and Johann Vollman and Heinrich Grausgruber for assistance in seed chemical analysis and Martin Pachner for SDS-PAGE analysis. 

 

 

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Cite this Article: Balcha A (2016). Variation in High Molecular Weight Glutenin Subunits and Seed Chemical Contents in Ethiopian Bread Wheat (Triticum aestivum L.) Varieties. Greener Journal of Agricultural Sciences, 6(8): 252-255, http://doi.org/10.15580/GJAS.2016.8.082416138.