QTL Detection and Candidate Gene Identification for Eating and Cooking Quality Traits in Rice (Oryza sativa L.) via a Genome-Wide Association Study.

The eating and cooking quality (ECQ) directly affects the taste of rice, being closely related to factors such as gelatinization temperature (GT), gel consistency (GC) and amylose content (AC). Mining the quantitative trait loci (QTLs), and gene loci controlling ECQ-related traits is vital. A genome-wide association study on ECQ-related traits was conducted, combining 1.2 million single nucleotide polymorphisms (SNPs) with the phenotypic data of 173 rice accessions. Two QTLs for GT, one for GC and five for AC were identified, of which two were found in previously reported genes, and six were newly found. There were 28 positional candidate genes in the region of qAC11. Based on a linkage disequilibrium (LD) analysis, three candidate genes were screened within the LD region associated with AC. There were significant differences between the haplotypes of LOC_Os11g10170, but no significant differences were found for the other two genes. The qRT-PCR results showed that the gene expression levels in the accessions with high ACs were significantly larger than those in the accessions with low ACs at 35d and 42d after flowering. Hap 2 and Hap 3 of LOC_Os11g10170 reduced the AC by 13.09% and 10.77%, respectively. These results provide a theoretical and material basis for improving the ECQ of rice.

A new allele PEL9 GG identified by genome-wide association study increases panicle elongation length in rice (Oryza sativa L.).

Considering the male sterile line has the phenomenon of panicle enclosure, panicle elongation length (PEL) plays an important role in hybrid rice seed production. However, the molecular mechanism underlying this process is poorly understood. In this study, we investigated the PEL phenotypic values of 353 rice accessions across six environments, which shows abundant phenotypic variation. Combining the 1.3 million single-nucleotide polymorphisms, we performed a genome-wide association study on PEL. Three quantitative trait loci (QTL) qPEL4, qPEL6, and qPEL9 were identified as significantly associated with PEL, of which qPEL4 and qPEL6 were previously reported QTLs and qPEL9 was novel. One causal gene locus, PEL9, was identified and validated. The PEL of accessions carrying allele PEL9 GG was significantly longer than that of those carrying allele PEL9 TT. We also demonstrated that the outcrossing rate of female parents carrying allele PEL9 GG increased by 14.81% compared with that of the isogenic line carrying allele PEL9 TT in an F1 hybrid seed production field. The allele frequency of PEL9GG increased gradually with an increase in latitude in the Northern Hemisphere. Our results should facilitate the improvement of the PEL of the female parent of hybrid rice.

QTL mapping and identification of candidate genes using a genome-wide association study for heat tolerance at anthesis in rice (Oryza sativa L.).

Heat tolerance (HT) of rice at anthesis is a key trait that ensures high and stable yields under heat stress. Finding the quantitative trait loci (QTLs) and gene loci controlling HT is crucial. We used relative spikelet fertility (RSF) as a measure of HT. The phenotypic values of RSF in 173 rice accessions were investigated in two environments and showed abundant variations. We performed a genome-wide association study on RSF using 1.2 million single nucleotide polymorphisms (SNPs). Five QTLs were significantly associated with RSF were identified, four were found in previously reported QTLs/genes, and one was novel. The novel QTL qRSF9.2 was mapped into the 22,059,984-22,259,984 bp region, which had 38 positional candidate genes. By combining the linkage disequilibrium analysis, the QTL region was narrowed to 22,110,508-22,187,677 bp, which contained 16 candidate genes. Among them, only gene LOC_Os09g38500 contained nonsynonymous SNPs that were significantly associated with RSF. In addition, accessions with large and small RSF values had corresponding respective high and low gene expression levels. Furthermore, the RSF of the CC allele was significantly higher than that of the TT allele. Hap 2 and Hap 3 can increase heat tolerance by 7.9 and 11.3%, respectively. Our results provide useful information that recommends further cloning of qRSF9.2 and breeding heat-tolerant rice varieties by marker-assisted selection.

Photocatalytic oxidation degradation of tetracycline over La/Co@TiO2 nanospheres under visible light.

The oxygen-vacancy-rich La/Co@TiO2 nanospheres for the photo catalytic degradation of tetracycline were prepared by a simple two-step method. 3 wt%La/Co@TiO2 nanospheres had better photocatalytic performance of the degradation of tetracycline than that of the other catalysts under visible light may be due to the synergistic effect between La/Co and TiO2 and nano-confined effect. The catalytic experimental results showed the degradation ratio of tetracycline (40 mg/L) were 100% for 90 min. XPS, Raman, and photoelectrochemical results showed appropriate number of oxygen vacancies existed on the surface of TiO2, which could improve the activation efficiency of dissolved oxygen in tetracycline solution because they accelerated the electron transfer rate in the system and inhibited the photoelectron-hole pair recombination under visible light. The EPR and radical scavenger tests showed h+, O2-, and ·OH were the main active species for the degradation of tetracycline. Also, the possible mechanism and intermediates of the tetracycline degradation process were speculated under the visible light. La/Co@TiO2 nanospheres would be a promising photocatalyst for wastewater treatment.

Ultra-selective desulfurization of 4, 6-dimethyldibenzothiophene via carbon-sulfur bond cleavage with the bimetal single atom on N-rGO.

A single-atom Cu and Ni anchored on N-doped Reduced Graphene Oxides, which confer the intensified exposure of interior active sites, was developed. Due to single-atom active sites which accelerated the oxygenation and hydrogenation, the prepared Cu/Ni-N-rGO shows excellent conversion, good stability and selectivity for CS bond cleavage by catalytic oxidation and hydrogenation at the different temperatures. The desulfurization ratio and selectivity for 4, 6-DMDBT to carbonhydrogen were 100 % and 100 %, respectively, on the suitable conditions. The kinetics of catalytic oxidation and in situ hydrogenation of 4, 6-DMDBT, and their mechanism over Cu/Ni-N-rGO by density functional theory was explored. Computational studies show the CS cleavage of the 4, 6-dimethyldibenzothiophene by catalytic oxidation and then in situ hydrogenation is easier than that by direct hydrogenation or catalytic oxidation.

Simultaneous removal of sulfides and benzene in FCC gasoline by in situ hydrogenation over NiLaIn/ZrO2-r-Al2O3.

The ZrO2-r-Al2O3 composite was developed and co-modified with nickel, lanthanum and indium species by the impregnation method. A fixed-bed reactor was utilized to investigate the activity of the resulting catalysts in the removal of sulfides and benzene in fluid catalytic cracking gasoline. The resultant samples were characterized using XRD, TEM, XPS, TGA, H2-TPR, NH3-TPD and N2 adsorption/desorption techniques. XRD analysis indicated no agglomeration of Ni and La species, in good agreement with the TEM image. Only under the suitable conditions of a metal loading of 15%, a reaction temperature of 423K, a reaction time of 60min, a space velocity of 3h-1, and a reaction pressure of 1MPa, could the desulfurization ratio, the debenzolization ratio, and selectivity of benzene to dimethylbutane and toluene reach 100%, 19.9%, 48.9% and 50.9%, respectively, and research octane number of the product increased by 2 units and sulfur content reached "Zero". The catalyst was actively involved in the in-situ hydrogenation under mild conditions and used for 30h with no loss in activity. This remarkable behavior makes the NiLaIn/ZrO2-r-Al2O3 family a potential candidate for industrial application as catalysts in the clean fuel.