Abstract
The eating and cooking qualities of rice grains are the major determinants of consumer preference and, consequently, the economic value of a specific rice variety. These two qualities are largely determined by the physicochemical properties of the starch, i.e. the starch composition, of the rice grain. In our study, we determined the genetic factors responsible for the physicochemical properties of starch in recombinant inbred lines (RILs) of japonica cv. Tainung 78 × indica cv. Taichung Sen 17 (TCS 17) cultivated over two crop seasons by examining palatability characteristics and several Rapid Viscosity Analyzer (RVA) parameters. Thirty-four quantitative trait loci (QTLs), each explaining between 1.2 and 78.1 % phenotypic variation, were mapped in clusters on eight chromosomes in 190 RILs genotyped with 139 markers. Ten pairs of QTLs were detected in the two environments, of which seven were in agreement with previous findings, suggesting that these QTLs may express stable experimental populations across various environments. Waxy (Wx), which controls amylose synthesis, was determined to be a primary gene regulating the physicochemical properties of cooked rice grains, as indicated by the presence of a major QTL cluster on chromosome 6 and by marker regression analysis. Six starch synthesis-related genes (SSRGs) which were located in the QTL intervals significantly differed in terms of gene expression between the two parents during grain-filling and were important genetic factors affecting physicochemical properties. The expression of four genes, PUL, ISA2, GBSSI, and SSII-3, was significantly upregulated in TCS 17, and this expression was positively correlated with six traits. The effects of the six SSRGs and gene interaction depended on genetic background and environment; grain quality may be fine tuned by selecting for SBE4 for japonica and PUL for indica. We provide valuable information for application in the breeding of new rice varieties as daily staple food and for use in industrial manufacturing by marker-assisted selection.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-014-0065-8) contains supplementary material, which is available to authorized users.
Highlights
Rice is one of the important cereal crops grown worldwide and is the major stable food for more than one-half of the world’s population, providing approximately 23 % of the daily caloric intake (Fischer et al 2000)
Variation in palatability and Rapid Viscosity Analyzer (RVA) profile parameters in the parents and recombinant inbred lines (RILs) population We evaluated eight physicochemical properties related to rice eating and cooking qualities (ECQ), including palatability and seven RVA parameters, in two parents and 190 RILs planted in two crop seasons
Based on the paired difference t test analysis, PLS and six RVA parameters, differed significantly in the RIL population between the two different crop seasons (ESM Table S3), indicating that the viscosity of the cooked rice grains was affected by the environment
Summary
Rice is one of the important cereal crops grown worldwide and is the major stable food for more than one-half of the world’s population, providing approximately 23 % of the daily caloric intake (Fischer et al 2000). Increasing grain yield has been an important breeding goal because the demand for rice is expected to increase by up to 40 % by 2030 (Khush 2005). In Taiwan, where rice is cultivated and harvested in two crop seasons every year, the breeding goal has focused on premium grain quality for the past 40 years. Rice starch, which accounts for approximately 90 % of the grain contents, is a valuable commodity and has been used in food and pharmaceuticals because of its bland taste, creamy texture, spreadability, and non-allergenicity (Wani et al 2012). Breeding new varieties with various grain qualities to meet these diverse purposes is an important target worldwide
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