Effects of Reduced Nitrogen Fertilization and Irrigation on Structure and Physicochemical Properties of Starch in Two Bread Wheat Cultivars

Jingyang Tong,Zhonghu He,Shujun Wang,Yan Zhang

doi:10.3390/agriculture11010026

Abstract

Nitrogen (N) fertilization and irrigation are significant agronomic factors affecting wheat production, but little information is available on the effects of reduced N fertilization and irrigation on internal starch structure and physicochemical properties associated with the quality of wheat-based foods. In this study, reduced N fertilization and irrigation were separately applied to investigate their effects on composition and morphological changes, crystalline and external region structure features, swelling power, and gelatinization characteristics of starch granules in bread wheat, with a high N-use-efficiency and water-saving wheat cultivar Zhongmai 175 and a widely grown cultivar Jingdong 17. Compared with a non-N control, reduced N fertilization did not change the crystallinity type and short-range ordered degree of starch; however, it significantly increased relative crystallinity, swelling power and gelatinization enthalpy, whereas amylose content and transition temperatures were decreased. Under reduced irrigation, more small starch granules with compact arrangements appeared in comparison with non-water control. Relative crystallinity, swelling power and gelatinization enthalpy of starch were increased, whereas short-range ordered degree and transition temperatures were decreased. Moreover, the starch of the two cultivars appeared to differ in response to both the N and water treatments. The findings indicated that reduced N fertilization or irrigation markedly influenced the structure and physicochemical characteristics of wheat starch, providing important information for developing elite cultivars with high N and water use efficiency and outstanding starch quality.

Highlights

Bread wheat (Triticum aestivum L.) is the most widely planted cereal crop and wheatbased foods are major constituents of the human diet worldwide [1]
With reduced N the amylose content of Zhongmai 175 and Jingdong 17 decreased from 30.78% to 29.96% and from 29.97% to 29.48%, respectively (Table 1), indicating that N fertilization affected the composition of starch in both cultivars, similar to Li et al [17] who conducted high N fertilization and both studies showed that low amylose content was associated with the applications of N fertilizers
Given that N applied at later growth stages could improve the activity of starch-branching enzymes in cereal grain [29,30], the decreased amylose content was attributed to enhanced starch-branching enzyme activity causing synthesis of high-amylopectin starch

Summary

Introduction

Bread wheat (Triticum aestivum L.) is the most widely planted cereal crop and wheatbased foods are major constituents of the human diet worldwide [1]. The most plentiful component of wheat grain is starch, which accounts for about 70% of the endosperm as well as 75% of flour dry weight. It provides calories for energy and plays an essential role in industry [2]. The relative contents of amylose and amylopectin are a key factor influencing morphological, internal structure and physicochemical properties of starch granules, including relative crystallinity, swelling power, and thermal and gelatinization properties [4,5,6]. Amylopectin content, the number of small starch granules, swelling power and gelatinization temperature are reported to positively influence the total scores of noodle and bread quality [9]

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Results

Conclusion