关键词：
Herbicide resistance;resistance management;resistance mechanism;weed control
摘要：
Since its initial introduction in the late 1950s, chemical control has dominated weed management practices in China. Not surprisingly, the development of herbicide resistance has become the biggest threat to long-term, sustainable weed management in China. Given that China has followed the same laissez-faire approach toward resistance management that has been practiced in developed countries such as the United States, herbicide resistance has evolved rapidly and increased steadily over the years. Previously, we carried out a systematic review to quantitatively assess herbicide-resistance issues in China. In this review, our main objective is to focus on mechanistic studies and management practices to document the (1) history of herbicide application in China; (2) resistance mechanisms governing the eight most resistance-prone herbicide groups, including acetolactate synthase inhibitors, acetyl-CoA carboxylase inhibitors, synthetic auxin herbicides, 5-enolpyruvylshikimate-3-phosphate synthase inhibitors, protoporphyrinogen oxidase inhibitors, photosystem I electron diverters, photosystem II inhibitors, and long-chain fatty-acid inhibitors; and (3) herbicide-resistance management strategies commonly used in China, including chemical, cultural, biological, physical, and integrated approaches. At the end, perspectives and future research are discussed to address the pressing need for the development of integrated herbicide-resistance management in China.
摘要：
The existing form of ionizable organic contaminants (IOCs) could affect their adsorption characteristics to soil and biochar. In this study, 2 IOCs, namely, sulfadiazine and imazalil, were selected to study their adsorption by rice straw-derived biochar-amended soils, as well as the effect of pH and gallic acid on their adsorption. The results showed that the soil adsorption isotherms of the two ionizable organic contaminants could be fitted well by a linear equation and the Freundlich equation, and r(2) was more than 0.80. The adsorption coefficient (Kd) in the three kinds of soil ranged from 0.262 to 4.07Lkg(-1) for sulfadiazine and from 3.11 to 96.5Lkg(-1) for imazalil. After the addition of biochar, the adsorption of sulfadiazine and imazalil in the soil increased. The adsorption of sulfadiazine by biochar gradually decreased with the increase in pH; the adsorption of imazalil increased when the pH increased from 2 to 5 and then gradually decreased with increasing pH. Gallic acid enhanced the adsorption of the two IOCs to pure soil and biochar-amended soil.
摘要：
Dimethoate, a systemic insecticide, has been used extensively in vegetable production. Insecticide residues in treated vegetables, however, pose a potential risk to consumers. Photocatalytic degradation is a new alternative to managing pesticide residues. In this study, the degradation of dimethoate in Bok choy was investigated under the field conditions using cerium-doped nano titanium dioxide (TiO2/Ce) hydrosol as a photocatalyst. The results show that TiO2/Ce hydrosol can accelerate the degradation of dimethoate in Bok choy. Specifically, the application of TiO2/Ce hydrosol significantly increased the reactive oxygen species (ROS) contents in the treated Bok choy, which speeds up the degradation of dimethoate. Ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) analysis detected three major degradation products, including omethoate, O,O,S-trimethyl thiophosphorothioate, and 1,2-Bis (acetyl-N-methyl-) methane disulfide. Two potential photodegradation pathways have been proposed based on the intermediate products. To understand the relationship between photodegradation and the molecular structure of target insecticides, we investigated the bond length, Mulliken atomic charge and frontier electron density of dimethoate using ab initio quantum analysis. These results suggest the P = S, P-S and S-C of dimethoate are the initiation sites for the photocatalytic reaction in Bok choy, which is consistent with our empirical data.
作者机构：
[徐世积; 何影; 李思齐] College of Plant Protection, Hunan Agricultural University, Changsha, 410128, China;Collaborative Innovation Center of Farmland Weeds Control, Loudi, 417000, China;[刘开林; 刘祥英; 周小毛; 柏连阳] College of Plant Protection, Hunan Agricultural University, Changsha, 410128, China<&wdkj&>Collaborative Innovation Center of Farmland Weeds Control, Loudi, 417000, China
通讯机构：
College of Plant Protection, Hunan Agricultural University, Changsha, China
摘要：
Burning straw in the field is a common agricultural practice. The effects of adding biochar derived from rice straw to soils on the phytotoxicity of sulfentrazone to Oryza sativa L. were observed. Overall, when 1 % biochar was added to three different soils, the phytotoxicity of sulfentrazone to O. sativa L. decreased, and the concentration that inhibits growth by 50 % (IC50) increased by 1.4 to 7.6 times. To illuminate the influencing mechanisms, the changes in sulfentrazone adsorption to the soil, the soil pH, and the bioavailable sulfentrazone extracted from the soil solution using hollow fiber-based liquid-phase microextraction were studied. The Freundlich constant (K
f
) of sulfentrazone to the soil increased 1.5 to 25 times relative to the K
f
in the three unamended soils, and the soil pH increased by 0.36 to 1.36 units resulted in a fraction of dissociated sulfentrazone increased by 10.2–17.4 %. In addition, the average concentrations of sulfentrazone in the three unamended soil solutions were 1.3–6.1 times relative to those in the three biochar-amended soil solutions. These results suggest that the sulfentrazone adsorption and soil pH increased when soils were amended with biochar, which decreased the bioavailable concentrations and reduced its phytotoxicity to O. sativa L.
摘要：
<jats:title>Abstract</jats:title><jats:p>The toxicity of ionizable organic compounds to organisms depends on the pH, which therefore affects risk assessments of these compounds. However, there is not a direct chemical method to predict the toxicity of ionizable organic compounds. To determine whether hollow-fiber liquid-phase microextraction (HF-LPME) is applicable for this purpose, a three-phase HF-LPME was used to measure sulfadiazine and estimate its toxicity to <jats:italic>Daphnia magna</jats:italic> in solutions of different pH. The result indicated that the sulfadiazine concentrations measured by HF-LPME decreased with increasing pH, which is consistent with the decreased toxicity. The concentration immobilize 50% of the daphnids (EC50) in 48 h calculated from nominal concentrations increased from 11.93 to 273.5 mg L<jats:sup>−1</jats:sup> as the pH increased from 6.0 to 8.5, and the coefficient of variation (CV) of the EC50 values reached 104.6%. When calculated from the concentrations measured by HF-LPME (pH 12 acceptor phase), the EC50 ranged from 223.4 to 394.6 mg L<jats:sup>−1</jats:sup>, and the CV decreased to 27.60%, suggesting that the concentrations measured by HF-LPME can be used to estimate the toxicity of sulfadiazine irrespective of the solution pH.</jats:p>
摘要：
Asia minor bluegrass (AmB) is a major weed impacting rapeseed production in Dongting Lake District, China. Growth chamber experiments were conducted to determine the influence of environmental factors on germination and emergence of AmB. The optimum constant temperature for germination was around 20 C. Seeds showed germination percentages above 60% under 22/15 and 24/19 C day/night temperature regimes. Seeds could germinate in the dark, but light exposure significantly enhanced the germination percentage. More than 50% of seeds germinated over a pH range between 4 and 10. Seeds were highly sensitive to osmotic stress, and germination was completely inhibited at an osmotic potential of -0.4 MPa, indicating that it was favored by a moist environment. Increasing salinity reduced germination of AmB seeds from 58% at 0 mM to 13% at 80 mM NaCl. The highest seedling emergence (62%) was observed when seeds were placed on the soil surface, and no seedlings emerged from seeds placed at a depth of 5 cm. This work shows that the climate and soil conditions in Dongting Lake District are suitable for AmB seed germination and that no-till fields, where seeds remain on the soil surface, promote the successful establishment of the weed.
摘要：
Plant microRNAs (miRNAs) play important roles as modulators of gene expression at the post-transcriptional level. Previous studies have shown that high-throughput sequencing is a powerful tool for the identification of miRNAs, and it is believed that many more miRNAs remain to be discovered. Here, we found 23 novel conserved miRNAs from three rice cultivars by high-throughput sequencing and further identified these through subsequent cloning and quantitative real-time polymerase chain reaction (qPCR). Eight of these novel miRNAs were detected with significant signals in the three rice cultivars by northern blotting assays. The quantitative analysis of their expression profiles showed that most of these miRNAs were perfectly or imperfectly negatively correlated with their target genes, which suggests that these miRNAs may play important roles during rice development. This is the first genome-wide investigation of miRNAs from different rice cultivars, and the data obtained expand the known rice miRNA inventory and provide further information about the regulatory roles played by miRNAs in rice development.
关键词：
Internal Ribosome Entry Site;Dwarf Virus;Internal Ribosome Entry Site Element;Internal Ribosome Entry Site Activity;Northern Blot Assay
摘要：
Rice black-streaked dwarf virus (RBSDV) is a recognized member of the genus Fijivirus, family Reoviridae. Genome segment S5 has a putative second ORF partially overlapping the major ORF but in a different reading frame. This putative ORF is present in a published sequence and in two Chinese isolates now sequenced. Antibodies were raised against purified P5-1 and P5-2 fusion proteins expressed in a prokaryotic system. In western blots, these antibodies reacted with proteins of about 106 and 27 kDa, respectively, as predicted by sequence analysis. In immunoelectron microscopy, antibodies to P5-1 reacted with viroplasms, indicating that P5-1 is a component of viroplasms, but no labeling was observed with P5-2 antisera. Northern blot assays showed that the genome segment S5 was transcribed as a single mRNA with no subgenomic RNA. These results show that S5 is functionally bicistronic in infected plants. Possible translational mechanisms for P5-2 are discussed.
