Effects of Wx and Its Interaction With SSIII-2 on Rice Eating and Cooking Qualities.

Bowen Yang,Xunchao Xiang,Shunju Xu,Liang Xu,Hui You

doi:10.3389/fpls.2018.00456

Bowen Yang, Xunchao Xiang + Show 3 more

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https://doi.org/10.3389/fpls.2018.00456

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Abstract

The Wx gene encodes a granule-bound starch synthase (GBSS) and plays a key role in determining rice eating and cooking qualities (ECQs). SSIII-2 (SSIIIa), a member of the soluble starch synthases, is responsible for the synthesis of long chains of amylopectin. To investigate the effects of Wx and its interaction with SSIII-2 on grain ECQs, a population from a hybrid combination was established as a research material. The genotypes of SSIII-2 and the single nucleotide polymorphisms (SNPs) on intron1, exon6, and exon10 of Wx, and the physicochemical indicators and rapid visco analyzer (RVA) profile characteristics were analyzed. The results revealed various effects of SSIII-2 on rice quality under different backgrounds of Wx alleles. There was no obvious difference between different SSIII-2 alleles under the same background of Wxa, whereas there was a significant diversity under the same background of Wxb. Wxa had a dominant epistasis to SSIII-2 because the effect of SSIII-2 was masked by the massive synthesis of GBSS under Wxa. The apparent amylose content (AAC) was mainly controlled by the In1G/T SNP, and rice gel consistency (GC) was regulated by the Ex10C/T SNP. The combined effects of three SNPs had a significant influence on all ECQs and RVA profile parameters, except for gelatinization temperature. In1T-Ex6A-Ex10C and In1T-Ex6A-Ex10T were classified as being low AAC type. TT-AA-CC and TT-AA-TT had a low AAC and a soft GC. The combined effects of different SNPs of Wx are very important for rice quality breeding.

Highlights

Rice yield has increased significantly over the past decade due to the introduction of semi-dwarfness and the exploitation of heterosis
There was no obvious difference in the tested characteristic values between different SSIII-2 alleles under the same background of Wxa (SNP of Wx loci with G)
The results of a multiple comparison showed that the alkaline spreading value (ASV), peak viscosity (PKV), BDV, and pasting temperature (PaT) varied significantly between different polymorphisms of the SSIII-2 alleles

Summary

Introduction

Rice yield has increased significantly over the past decade due to the introduction of semi-dwarfness and the exploitation of heterosis. With the constantly increasing demands from society, rice quality cannot meet the requirements of consumers. Wx and SSIII-2 Regulate ECQs. Rice quality is determined by starch, which is composed of two polysaccharides: amylose and amylopectin. According to the standard Chinese rice resources evaluation, AAC can be classified as waxy (0–2%), very low (2–10%), low (10–20%), intermediate (20–25%), and high (25–33%). The most important indices of grain quality are eating and cooking qualities (ECQs) that are determined by three physical and chemical indices: AAC, rice gel consistency (GC), and gelatinization temperature (GT). A rice starch rapid visco analyzer (RVA) is widely used to evaluate rice grain quality because it provides a rapid and accurate determination of ECQs for a small amount of sample (Bao and Xia, 1999)

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