Inheritance of resistance to fenoxaprop‐p‐ethyl in sprangletop (Leptochloa chinensis L. Nees)

Sprangletop (Leptochloa chinensis L. Nees) is a serious grass weed in direct‐seeded rice cropping systems in Thailand. One population of sprangletop, BLC1, was found to be resistant to fenoxaprop‐p‐ethyl at 62‐fold the concentration of a susceptible biotype, SLC1. This study elucidated the inheritance of resistance to fenoxaprop‐p‐ethyl in this sprangletop BLC1 genotype. The reaction to the herbicide at 0.12–2.4 mg ai L^?1 was determined in the seedlings of self‐pollinated resistant BLC1, susceptible SLC1 and SLC1 that had been allowed to cross‐pollinate with BLC1. At 0.24 mg ai L^?1, all the seedlings of SLC1 were killed, while 99% of BLC1 survived, along with 5% of the cross‐pollinated SLC1 seedlings, which were considered to be putative F₁ hybrids. The root and shoot lengths of the F₁ hybrids in 0.24 mg ai L^?1 of fenoxaprop‐p‐ethyl, relative to those in the absence of the herbicide, were close to or the same as the resistant parent, indicating that the resistance is a nearly complete to complete dominant trait. One‐hundred‐and‐forty‐one of the F₂‐derived F₃ families were classified by their response to the herbicide at 0.24 and 0.48 mg ai L^?1 into 39 homozygous susceptible : 72 segregating : 30 homozygous resistant, fitted with a 1:2:1 ratio at χ² = 1.21 and P = 0.56, indicating that the resistance to fenoxaprop‐p‐ethyl in the sprangletop BLC1 genotype is controlled by a single gene.     

Involvement of cytochrome P‐450 enzyme activity in the selectivity and safening action of pyrazosulfuron‐ethyl

To investigate the selectivity and safening action of the sulfonylurea herbicide pyrazosulfuron‐ethyl (PSE), pyrazosulfuron‐ethyl O‐demethylase (PSEOD) activity involving oxidative metabolism by cytochrome P‐450 was studied in rice (Oryza sativa L cv Nipponbare) and Cyperus serotinus Rottb. Cytochrome P‐450‐dependent activity was demonstrated by the use of the inducers 1,8‐naphthalic anhydride and ethanol, the herbicides PSE, bensulfuron‐methyl, dimepiperate and dymron, or the inhibitor piperonyl butoxide (PBO). Growth inhibition in C serotinus seedlings was more severe than that in rice seedlings. O‐Dealkylation activities of PSE were induced differently in rice and in C serotinus, with distinctly higher activity in rice seedlings. The induced PSEOD activities were slightly inhibited by PBO in rice seedlings, whereas they were strongly inhibited in C serotinus seedlings. Dimepiperate and dymron were effective safeners of rice against PSE treatment. Treatments with herbicide alone resulted in less induction of PSEOD activity compared with combined treatments of the herbicide and safener. PSEOD activity in rice seedlings induced with herbicide alone was strongly inhibited by PBO, whereas it was weakly inhibited in rice seedlings induced with combinations of PSE and two safeners. These results suggest that O‐demethylation by cytochrome P‐450 enzymes may be involved in the metabolism of PSE and may contribute to its selectivity and safening action. Furthermore, these results suggest the existence of a multiple form of cytochrome P‐450 in plants. © 2001 Society of Chemical Industry     

呋虫胺及其代谢物在水稻生态系统中的残留检测与消解动态

为评价呋虫胺在水稻生态系统中的残留与消解行为,分别在海南、湖南和黑龙江省3地进行了规范残留试验。建立了超高效液相色谱-串联质谱 (UPLC-MS/MS) 检测呋虫胺 (DNF) 及其代谢物1-甲基-3-[(3-四氢呋喃) 甲基]脲 (UF) 与1-甲基-3-[(3-四氢呋喃) 甲基]二氢胍盐 (DN) 在水稻稻株、土壤、田水、糙米和稻壳中残留的分析方法。样品经含体积分数为1%的乙酸水溶液或乙腈溶液提取,QuEChERS方法净化,以甲醇-水混合溶液为流动相梯度洗脱,多反应监测 (MRM) 模式扫描,外标法定量。结果表明:3种分析物的进样浓度与其峰面积之间呈良好线性相关,R2>0.999。DNF、UF和DN在稻株、土壤、田水、糙米和稻壳中的平均回收率在71%~102%之间,在稻株、土壤、田水和糙米中的相对标准偏差 (RSD) 在1.2%~8.3%之间,在稻壳中的RSD在4.4%~20%之间。3种分析物在稻株、土壤、田水、糙米和稻壳中的最低检测浓度 (LOQ) 分别为0.1 mg/kg、0.02 mg/kg、0.01 mg/L、0.02 mg/kg和0.1 mg/kg。DNF、UF和DN的最小检出量分别为1、0.4和4 pg。3种分析物的消解半衰期分别为:DNF在稻株上为0.41~2.7 d,土壤中为1.6~4.2 d,田水中为0.90~2.2 d;DN在稻株上为2.9~13 d,土壤中为64~65 d,田水中为4.2 d;UF在稻株上为0.43~3.1 d。20%呋虫胺悬浮剂以有效成分120~180 g/hm2的剂量于水稻抽穗期施用2~3次,施药间隔期21 d,分别于距末次施药后14 d与21 d采收,呋虫胺在糙米中的残留最大值为0.11 mg/kg,低于中国制定的其在糙米上的最大残留限量标准1 mg/kg。     

Residues of zeta‐cypermethrin in bovine tissues and milk following pour‐on and spray application

The depletion of zeta‐cypermethrin residues in bovine tissues and milk was studied. Beef cattle were treated three times at 3‐week intervals with 1 ml 10 kg^?1 body weight of a 25 g litre^?1 or 50 g litre^?1 pour‐on formulation (2.5 and 5.0 mg zeta‐cypermethrin kg^?1 body weight) or 100 mg kg^?1 spray to simulate a likely worst‐case treatment regime. Friesian and Jersey dairy cows were treated once with 2.5 mg zeta‐cypermethrin kg^?1 in a pour‐on formulation. Muscle, liver and kidney residue concentrations were generally less than the limit of detection (LOD = 0.01 mg kg^?1). Residues in renal‐fat and back‐fat samples from animals treated with 2.5 mg kg^?1 all exceeded the limit of quantitation (LOQ = 0.05 mg kg^?1), peaking at 10 days after treatment. Only two of five kidney fat samples were above the LOQ after 34 days, but none of the back‐fat samples exceeded the LOQ at 28 days after treatment. Following spray treatments, fat residues were detectable in some animals but were below the LOQ at all sampling intervals. Zeta‐cypermethrin was quantifiable (LOQ = 0.01 mg kg^?1) in only one whole‐milk sample from the Friesian cows (0.015 mg kg^?1, 2 days after treatment). In whole milk from Jersey cows, the mean concentration of zeta‐cypermethrin peaked 1 day after treatment, at 0.015 mg kg^?1, and the highest individual sample concentration was 0.025 mg kg^?1 at 3 days after treatment. Residues in milk were not quantifiable beginning 4 days after treatment. The mean concentrations of zeta‐cypermethrin in milk fat from Friesian and Jersey cows peaked two days after treatment at 0.197 mg kg^?1 and 0.377 mg kg^?1, respectively, and the highest individual sample concentrations were 2 days after treatment at 0.47 mg kg^?1 and 0.98 mg kg^?1, respectively. © 2001 Society of Chemical Industry     

新烟碱类杀虫剂吡虫啉、噻虫啉和啶虫脒及代谢物在水稻及非靶标水生生物中的痕量检测方法及其应用

为了阐明新烟碱类杀虫剂对水稻和非靶标水生生物的残留特性和安全性, 建立了水稻、非靶标水生生物斑马鱼Danio rerio和大型溞Daphnia magna、水体中3种新烟碱类杀虫剂(吡虫啉、噻虫啉、啶虫脒)及其7种代谢物的痕量检测分析方法。采用QuEChERS方法进行样品前处理, 高效液相色谱－串联质谱检测, 目标化合物均采用外标法定量。结果表明:10种目标化合物的溶剂标准曲线和基质标准曲线在1~1 000 μg/kg范围内线性关系良好, 决定系数为0.991~0.999; 10种目标化合物在6种基质中的平均回收率为71.16%~118.57%, 相对标准偏差为0.54%~18.04%, 水稻、斑马鱼、营养液和水中10种目标化合物的定量限为10 μg/kg(大型溞中的定量限为50 μg/kg), 满足残留分析方法的要求。运用所建立的方法探究了3种新烟碱类杀虫剂在水稻及非靶标水生生物(斑马鱼和大型溞)中的吸收累积和代谢行为, 结果表明这3种农药在水稻中的转运系数均大于7, 极易向地上部分迁移; 在非靶标水生生物中的富集系数均小于2 mL/g, 为低富集性农药。     

Root‐associated microbes in sustainable agriculture: models,metabolites and mechanisms

Since the discovery of penicillin in 1928 and throughout the ‘age of antibiotics’ from the 1940s until the 1980s, the detection of novel antibiotics was restricted by lack of knowledge about the distribution and ecology of antibiotic producers in nature. The discovery that a phenazine compound produced by Pseudomonas bacteria could suppress soilborne plant pathogens, and its recovery from rhizosphere soil in 1990, provided the first incontrovertible evidence that natural metabolites could control plant pathogens in the environment and opened a new era in biological control by root‐associated rhizobacteria. More recently, the advent of genomics, the availability of highly sensitive bioanalytical instrumentation, and the discovery of protective endophytes have accelerated progress toward overcoming many of the impediments that until now have limited the exploitation of beneficial plant‐associated microbes to enhance agricultural sustainability. Here, we present key developments that have established the importance of these microbes in the control of pathogens, discuss concepts resulting from the exploration of classical model systems, and highlight advances emerging from ongoing investigations. © 2019 Society of Chemical Industry     

Residues of the algicide endothal in water,soil and rice,after paddy field applications

In order to obtain residue data from the application of the algicide endothal in Italian rice paddy fields, two experiments were carried out using a 50 g kg^?1 granular formulation in a small pond and the same granular and two liquid formulations in actual paddy fields of the Italian rice growing area. Endothal decay in the pond water was very rapid, reaching residue levels of 0·01-1·02 mg litre^?1 in two days and 0·004-0·01 mg litre^?1 at the third day. The muddy soil of the pond was free from measurable endothal residues( <0·02 mg kg^?1). In the paddy-field waters, the endothal decay was slower, with an average half-life time of 3·3 days, independently of the type of formulation. The actual residues in water after 6 days ranged from 0·3 to 1·3 mg litre^?1 according to the initial amount of product applied, and, consequently, to the initial concentration in water. Rice samples collected at the normal harvest time from the two paddy fields, treated with three different formulations, showed no endothal residue at the minimum detectable level of 0·01 mg kg^?1.     

Uptake,translocation and metabolism of the herbicide molinate in tobacco and rice

Molinate, a selective herbicide, is used for the control of annual and perennial weeds in rice paddy fields. This study was designed to assess the basis of the selective action of molinate between a susceptible broadleaf crop, tobacco, and a resistant graminaceous plant, rice. Experiments were conducted comparing plant growth under different concentrations of molinate, determining the absorption and translocation of the herbicide in the plant and identifying the metabolites in suspension cells. Rice showed greater tolerance to molinate than tobacco. Leaves of tobacco showed retarded and distorted growth at 10 mg liter^-1 of molinate 14 days after treatment, but rice leaves were unaffected at this concentration. Higher concentrations of molinate accumulating in the root of tobacco seedlings may inhibit root development and represent a significant factor in the herbicide's selective action. Seven and eight metabolites were found in tobacco and rice cells, respectively, with molinate sulfoxide and molinate sulfone present in both species. © 1998 SCI