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.
Rice is a major food source for much of the world, and expanding our knowledge of genes conferring specific rice grain attributes will benefit both farmer and consumer. Here we present novel dull grain mutants with a low amylose content (AC) derived from mutagenesis of Oryza sativa, ssp. japonica cv. Taikeng 8 (TK8). Positional cloning of the gene conferring the dull grain phenotype revealed a point mutation located at the acceptor splice site of intron 11 of FLOURY ENDOSPERM2 (FLO2), encoding a tetratricopeptide repeat domain (TPR)-containing protein. Three novel flo2 alleles were identified herein, which surprisingly conferred dull rather than floury grains. The allelic diversity of flo2 perturbed the expression of starch synthesis-related genes including OsAGPL2, OsAGPS2b, OsGBSSI, OsBEI, OsBEIIb, OsISA1, and OsPUL. The effect of the flo2 mutations on the physicochemical properties of the grain included a low breakdown, setback, and consistency of rice, indicating a good elasticity and soft texture of cooked rice grains. The effects of FLO2, combined with the genetic background of the germplasm and environmental effects, resulted in a variety of different amylose content levels, grain appearance, and physicochemical properties of rice, providing a host of useful information to future grain-quality research and breeding.
In their article, Wang et al.[1] report a new scheme for THz heterodyne detection using a laser-driven LTG-GaAs photomixer [2,3] and make the impressive claim of achieving near quantum-limited sensitivity at room temperature. Unfortunately, their experimental methodology is incorrect, and furthermore the paper provides no information on the mixer conversion loss, an important quantity that could readily have been measured and reported as a consistency check. The paper thus offers no reliable experimental evidence that substantiates the claimed sensitivities. To the contrary, the very high value reported for their photomixer impedance strongly suggests that the conversion loss is quite poor and that the actual sensitivity is far worse than claimed.THz heterodyne detection has been used in astronomy for over three decades [4] and is primarily of interest for high-resolution spectroscopy [5]. An illustrative application is the measurement of rotational transitions of isotopologues of water vapor to estimate the D/H ratio in comets -indeed, recent data from the SOFIA airborne observatory have reactivated the debate on whether the water in the Earth's oceans was delivered by comets [6]. To date, the best detection sensitivities have been achieved using cryocooled superconducting devices [5] such as the superconductor-insulator-superconductor (SIS) receivers that enable ALMA [7] or the hot-electron bolometers (HEB) used in the HIFI instrument on the Herschel 1
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