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dcyphr | Wheat (Triticum aestivum L.) Breeding from 1891 to 2010 Contributed to Increasing Yield and Glutenin Contents but Decreasing Protein and Gliadin Contents

Abstract

The composition of wheat protein may trigger celiac disease. This study compares 60 types of wheat grown over 3 years for things like height, yield, protein, gliadin, glutenin, albumin/globulin ratio, and gluten. When looking at proteins, this study found that the year of harvest, not the type of plant, had a larger effect. This study did not find evidence supporting modern wheat varieties triggering celiac disease more than other types of wheat.

Aims

This study aims to identify if different types of wheat are more likely to trigger celiac disease based on the specific protein composition of that wheat.

Introduction

The proteins in wheat can be classified by if they are soluble in solutions of water or alcohol. Albumins and globulins are water soluble, and gliadins are soluble in 70% alcohol. Wheat can cause reactions like celiac disease (CD), wheat allergy, and non-celiac gluten sensitivity (NCGS). Although we know what causes CD and wheat allergies, it is not 100% clear on what causes NCGS. One theory is that the proteins in wheat are the cause. Prevalence of CD and NCGS have increased over the past 50 years, and possible explanations of that are changes in the human immune system, the processing of wheat in foods, or the process of growing the wheat. This study assesses types of wheat grown from 1891 to 2010, with everything from 1950 to 2010 considered modern wheat.

Results

Agronomic Characteristics

Plant height decreased form 117-153cm old wheat plants to the 76-99cm modern wheat plants. The yield and harvest index, however, were much higher in the modern plants compared to the old plants. 


Crude Protein Contents

The protein content was variable for all three years, but 90% of the plants had a protein content of less than 10%.


Percentages of Albumins/globulins, Gliadins, Glutenins, and Gluten

Albumins/globulins had no significant change in this study. Gliadins had a significant decrease from old to modern plants. On the contrary, the glutenins had a steady increase from old to modern plants. Gluten is the sum of gliadins and glutenins, so it did not have a significant change because the individual changes cancel each other out. 


Correlations between Agronomic and Proteomic Characteristics

As the plant height decreased, the yield and harvest index increased. With a high yield, there was a lower spike density, but a higher harvest index. There were some weak correlations between different protein types within the gliadin proteins to plant height, yield, and spike density which are represented in the original article. 


Influence of Genotype and Harvest Year on the Protein Distribution

The study of genotypes showed that the year of harvest was more important in the proportions of albumin/globulin and glutenin than the variety of plant. Gliadin was the only protein that was more influenced by the variety of plant than of the harvest year. 

Discussion

The data in this study about plant height agrees with a previous study done on wheat, and the ideal plant height is 80-100cm. If the wheat in this study had been fertilized, the protein content would have been much higher, but this study was interested in testing without the influence of fertilizer. There are mixed results in studies that test the change in protein content from varieties of wheat used from 1860 to 2000. Unlike this study, other studies have found there was a protein increase over time. The decrease in gliadin and increase in glutenin over time found in this study agrees with another previous study that was done. There was no evidence on the specific protein type that tends to cause CD being elevated in modern wheat. In the few studies done on this topic, there are also mixed results.

Methods

The 60 varieties of wheat were selected from the Leibniz Institute of Plant Genetics and Crop Plant Research, and were grown under similar conditions in 2015, 2016, and 2017.The albumin/globulins, gliadins, and glutenins were extracted from the wheat, and  Reverse Phase 

High Performance Liquid Chromatography was used to analyze the samples.

Conclusion

This study has identified some important trends in modern wheat plants compared to old wheat plants, but has yet to identify a trend that explains the recent increase in celiac disease, wheat allergy, and non-celiac gluten sensitivity.