qFC6, a major gene for crude fat content and quality in rice.

KEY MESSAGE: qFC6, a major quantitative trait locus for rice crude fat content, was fine mapped to be identical with Wx. FC6 negatively regulates crude fat content and rice quality. Starch, protein and lipids are the three major components in rice endosperm. The lipids content in rice influences both storage and quality. In this study, we identified a quantitative trait locus (QTL), qFC6, for crude fat (free lipids) content through association analysis and linkage analysis. Gene-based association analysis revealed that LOC_Os06g04200, also known as Wx, was the candidate gene for qFC6. Complementation and knockout transgenic lines revealed that Wx negatively regulates crude fat content. Lipid composition and content analysis by gas chromatography and taste evaluation analysis showed that FC6 positively influenced bound lipids content and negatively affected both free lipids content and taste. Besides, higher free lipids content rice varieties exhibit more lustrous appearance after cooking and by adding extra oil during cooking could improve rice luster and taste score, indicating that higher free lipids content may make rice more lustrous and delicious. Together, we cloned a QTL coordinating rice crude fat content and eating quality and assisted in uncovering the genetic basis of rice lipid content and in the improvement of rice eating quality.

Deep eutectic solvent-based ultrasound-assisted emulsification microextraction for the rapid determination of benzotriazole and benzothiazole derivatives in surface water samples.

This work describes a simple and environmental-friendly method for the simultaneous determination of five benzotriazole derivatives (BTRs) and four benzothiazole derivatives (BTs) that are frequently found in surface water. The target analytes were efficiently extracted from water samples using a "green" deep eutectic solvent (DES) as the extraction solvent based- ultrasound-assisted emulsification microextraction (DES-USAEME), and their determination were performed by ultrahigh-performance liquid chromatography and electrospray ionization (+)-quadrupole time-of-flight mass spectrometry (UHPLC-ESI(+)-QToF-MS). The DES was composed of a mixture of choline chloride and phenol (molar ratio 1:2). The DES-USAEME factors were optimized by a Box-Behnken Design coupled response surface methodology. The developed method was validated, providing limits of quantitation (LOQs; 02 µg L-1), high precisions (1-8%), and satisfactory mean spiked recoveries (72-104 %). Relatively high total concentrations of the target analytes were found in samples collected from a reservoir (47.2-101.3 µg L-1), which may have been released from tire-wear particles and scrap tires from buses and old tires that were strung alongside the shuttle boats to prevent the boats from coming into contact with each other or from impacting against the dock during docking. This is the first study on the occurrence of BTRs and BTs in reservoir samples.

Genetic architecture and key genes controlling the diversity of oil composition in rice grains.

Rice grain oil is a valuable nutrient source. However, the genetic basis of oil biosynthesis in rice grains remains unclear. In this study, we performed a genome-wide association study on oil composition and oil concentration in a diverse panel of 533 cultivated rice accessions. High variation for 11 oil-related traits was observed, and the oil composition of rice grains showed differentiation among the subpopulations. We identified 46 loci that are significantly associated with grain oil concentration or composition, 16 of which were detected in three recombinant inbred line populations. Twenty-six candidate genes encoding enzymes involved in oil metabolism were identified from these 46 loci, four of which (PAL6, LIN6, MYR2, and ARA6) were found to contribute to natural variation in oil composition and to show differentiation among the subpopulations. Interestingly, population genetic analyses revealed that specific haplotypes of PAL6 and LIN6 have been selected in japonica rice. Based on these results, we propose a possible oil biosynthetic pathway in rice grains. Collectively, our results provide new insights into the genetic basis of oil biosynthesis in rice grains and can facilitate marker-based breeding of rice varieties with enhanced oil and grain quality.

Determination of microcystins in water samples by deep eutectic solvent-based vortex-assisted liquid-liquid microextraction coupled with ultrahigh-performance liquid chromatography-high resolution mass spectrometry.

Rapid screening of two microcystins (i.e., microcystin-YR (MC-YR) and microcystin-LR (MC-LR)) in surface water samples was performed by a simple and eco-friendly procedure using deep eutectic solvent-based vortex-assisted liquid-liquid microextraction (DES-based VALLME) combined with ultrahigh-performance liquid chromatography and electrospray ionization (+)-quadrupole time-of-flight mass spectrometry (UHPLC-ESI(+)-qTOF-MS) detection. To obtain an efficient water-miscible DES, choline chloride and phenol at a molar ratio of 1 : 2 were used as an extractant for VALLME. To optimize factors of DES-based VALLME, response surface design alongside Box-Behnken design was used. The limits of quantitation (LOQs) were 0.5 ng mL-1 and 0.4 ng mL-1 for MC-YR and MC-LR, respectively, which is sensitive enough to meet the World Health Organization (WHO) maximum guideline level for MC-LR in water of 1.0 ng mL-1. Moreover, satisfactory precision with relative standard deviations (RSD) for both intra- and inter-day analysis lower than 11%, and trueness (also known as mean extraction recovery) ranged from 85.5 to 113% based on the ICH method validation guideline.

Development and evaluation of near-isogenic lines for brown planthopper resistance in rice cv. 9311.

Brown planthopper (BPH) is the most destructive pest of rice in Asia. To date 29 BPH resistance genes have been identified, but only a few genes are being used in breeding due to inefficient markers for marker-assisted selection (MAS) and little knowledge of the real effects of the genes. In this study we individually transferred 13 genes or QTLs (Bph14, QBph3, QBph4, Bph17, Bph15, Bph20, Bph24, Bph6, Bph3, Bph9, Bph10, Bph18 and Bph21) into cultivar 9311 by marker assisted backcross breeding (MABB). Through positive and negative selection we narrowed the segments from donors containing Bph14, Bph15, Bph6 and Bph9 to 100-400 kb. Whole-genome background selection based on a high resolution SNP array was performed to maximize reconstitution of the recurrent parent genome (RPG 99.2-99.9%). All genes reduced BPH growth and development and showed antibiotic responses in seedlings. Based on genetic effects and amino acid sequences of genes in three clusters we inferred that Bph10 and Bph21 might be identical to Bph26, whereas Bph9 and Bph18 were different. Bph15 might be same with Bph17, but QBph4, Bph20 and Bph24 might be different. We believe that these NILs will be useful in rice BPH resistance research and breeding.