Degradation of Herbicides Atrazine and Bentazone Applied Alone and in Combination in Soils

The application of a mixture of bentazone(3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide)and atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine)is a practical approach to enhance the herbicidal effect.Labo- ratory incubation experiments were performed to study the degradation of bentazone and atrazine applied in combination and individually in maize rhizosphere and non-rhizosphere soils.After a lag phase,the degradation of each individual herbicide in the non-autoclaved soil could be adequately described using a first-order kinetic equation.During a 30-d in- cubation,in the autoclaved rhizosphere soil,bentazone and atrazine did not noticeably degrade,but in the non-autoclaved soil,they rapidly degraded in both non-rhizosphere and rhizosphere soils with half-lives of 19.9 and 20.2 d for bentazone and 29.1 and 25.7 d for atrazine,respectively.The rhizosphere effect significantly enhanced the degradation of atrazine, but had no significant effect on bentazone.These results indicated that biological degradation accounted for the degrada- tion of both herbicides in the soil.When compared with the degradation of the herbicide applied alone,the degradation rates of the herbicides applied in combination in the soils were lower and the lag phase increased.With the addition of a surfactant,Tween-20,a reduced lag phase of degradation was observed for both herbicides applied in combination. The degradation rate of bentazone accelerated,whereas that of atrazine remained nearly unchanged.Thus,when these two herbicides were used simultaneously,their persistence in the soil was generally prolonged,and the environmental contamination potential increased.

Removal of bentazone from micro-polluted water using MIEX resin:Kinetics,equilibrium,and mechanism

The contamination of surface and ground water by bentazone has attracted increasing global concern in recent years. We conducted a detailed investigation using MIEX resin to eliminate bentazone from waters. Batch experiments were carried out to evaluate the effect of process parameters, such as retention time, resin amount, and initial pesticide concentration, on removal efficiency of bentazone. Results showed the sorption process was fast and bentazone could be efficiently removed in 30 minutes. The kinetic process of bentazone sorption on MIEX resin was well described by pseudo second-order model and intraparticle diffusion was the rate controlling step. The MIEX resin possessed the highest sorption capacity of 0.2656 mmol/mL for bentazone according to Langmuir fitting, Bentazone is a hydrophobic ionizable organic compound, and both ionic charge and hydrophobic aromatic structure governed the sorption characteristics on MIEX resin. The different removal efficiencies of ionic and non-ionic pesticides, combined with the charge balance equations of bentazone, SO4^2-, NO3- and Cl-, indicated that removal of bentazone using MIEX resin occurred primarily via ion exchange.

Development of RAPD Markers and SCAR Markers Linked to Bentazon Susceptible Lethality Gene in Rice

Rice cultivar Norin 8 and its mutant Norin 8m harbour bentazon resistance trait and bentazon susceptibility trait respectively. A total of 360 arbitrary 10-mer oligonucleotide primers were screened on the genomic DNA of Norin 8 and Norin 8m with RAPD technique. Among which, five primers produced seven polymorphic RAPD bands between Norin 8 and Norin 8m. Amplified RAPD polymorphic products were cloned and sequenced. The sequences were used to design primers for PCR. Five SCAR markers, SCAR/G18/883, SCAR/G18/890, SCAR/G18/919/948, SCAR/D10/1237 and SCAR/F03/1186, were developed from OPG18/943, OPG18/972, OPD10/1248 and OPF03/1198. F-2 progeny of 320 individuals was analyzed to map SCAR markers in relationship to ben or Ben genes. SCAR markers of SCAR/G18/883, SCAR/G18/890, SCAR/G18/919/948 were shown to cosegregate with ben or Ben genes, and SCAR/D10/1237 to be linked of Ben gene with a distance of (14.8 +/- 2.1) cM. The genetic linkage to ben gene and SCAR markers was identified by a pair of near isogenic lines H121 and Hben121. Southern blotting analysis and segregation ratio of F-2 progeny revealed that OPG18/943 and OPG18/972 were single-copy in genome, and locus of OPG18/943 and OPG18/972 were allelic and sequence tagged sites. It is the first report on molecular markers linked to ben or Ben genes. The markers are useful to marker-assisted selection for the breeding and tag ben gene with map-based cloning.

The Application of Bentazon Susceptible Gene on Seed Production of Hybrid Rice

The seed production of male and female parent of ‘Hunzhi 1＇ contained bentazon susceptible gene was studied. The result showed that spraying 3. 375 L/hm2 48% bentazon aqua could control the self-pollinated fertilization rate below 1.0% and survival plant rate was 0. The spray of bentazon would not influence MC526 pollen vitality. Seed setting rate of female parent was not obvious different from that of control group with spraying bentazon aqua more than 3. 375 L/hm^2 from the sprouting appearing period to full heading stage. This demonstrated that bentazon aqua had no influence on seed setting rate during florescence of female parent. The weight ratio between male parent seeds and female parent seeds was 1 to 5, then seeds from parents with that weight ratio would be mixedly planted for seed production. With this weight ratio, relative proper structure of panicle and grain would be obtained ,panicle ratio was 1 to 4.3, glumous flowers ratio was 1 to 3.5. Cross seed-setting rate of female parent was 72.6% and seed production per hm^2 was 66 000 kg.

Research Progress on Mechanized Mixed Sowing Seed Production Technology of Hybrid Rice

Hybrid rice planting has been widely popularized and applied in the world. However, the high cost of seed production and the complicated procedures have become a bottleneck in the development of hybrid rice. The research progress on mixed sowing seed production techniques of hybrid rice was introduced from the aspects of rice resources creation, breeding, sowing seed technology research and cost benefit analysis. The production technology of the new mixed seeding combina- tion ＂Xinhunyou 6＂ was investigated, including the research and validation of benta- zon treatment period and dosage, mixing ratio of male and female parents, and the comparative test of different different sowing methods, which revealed that the mechanization technology of seed production of hybrid rice was mature and feasible and would be one of the most important development trend of technological devel- opment of hybrid rice production.

Selection of Submergence Tolerant Homozygous Line by STS Marker and Twice Submergence Stress

One sequence tagged site marker Subl-1 and twice submergence stress method were used in selection of submergence tolerant homozygous line from Sub-lBS, a submergence tolerant, bentazon sensitive and photoperiod-sensitive and/or thermo-sensitive genic male sterile line that developed by our laboratory. The results revealed that the original Sub-lBS was heterozygous in SublA-1 locus even though it was identical in almost all of agronomical traits and the segregation of SublA-1 was in accordance with Mendelian law based on chi-square test. And then the original Sub-IBS was divided into two groups： one was ofSublA-1 introgression and the other was not; and the two groups were tested by twice submergence stress method. After the first submergence stress that lasted for 12 d, the average plant heights were significant difference at the 1% level between the two groups. After recovery for 10 d, the second submergence stress sustained for 18 d was carried on; and the group with SublA-1 gene was found apparently tolerant than the other group in submergence tolerance.

SCAR Markers Assisted Selection for a Bentazon Susceptible Lethality Gene (ben) in Rice

In progenies resulting from crosses involving rice cultivar Norin 8m susceptible to bentazon as the donor of ben gene, SCARs tightly linked to ben were utilized for selection of ben. The homozygous and heterozygous genotypes with ben could be identified with the SCARs. The molecular markers offer a powerful tool for indirect selection of ben and can accelerate the introgression of ben into current rice cultivars.

Sensitivity of Adzuki Bean (<i>Vigna angularis</i>) to Acifluorfen, Fomesafen, Bentazon, Imazethapyr and Halosulfuron-Methyl Applied Postemergence

New herbicide options are needed for postemergence (POST) broadleaf weed control in adzuki bean. A field study, of five experiments, was conducted over a three-year period (2014, 2015, 2016) in Ontario to evaluate the tolerance of adzuki bean to the POST application of acifluorfen (600 and 1200 g&middot;ai&middot;ha-1), fomesafen (240 and 480 g&middot;ai&middot;ha-1), bentazon (1080 and 2160 g&middot;ai&middot;ha-1), imazethapyr (100 and 200 g&middot;ai&middot;ha-1) and halosulfuron-methyl (75 and 150 g&middot;ai&middot;ha-1). Acifluorfen and fomesafen applied POST caused as much as 12% visible injury at the 1X rate and 20% visible injury at the 2X rate but had no adverse effect on adzuki bean population, shoot dry weight, height, maturity or yield. Bentazon caused as much as 23% visible injury at 1080 g&middot;ai&middot;ha-1 and 28% visible injury at 2160 g&middot;ai&middot;ha-1 but caused no adverse effect on adzuki bean population, shoot dry weight, height, maturity or yield at either rate, except at 2160 g&middot;ai&middot;ha-1 which reduced shoot dry weight 20% and height 12%. Imazethapyr caused as much as 22% visible injury at 100 g&middot;ai&middot;ha-1 and 34% visible injury at 200 g&middot;ai&middot;ha-1 but caused no adverse effect on adzuki bean population, shoot dry weight, height, maturity or yield at either rate except at 200 g&middot;ai&middot;ha-1 which delayed maturity slightly. Halosulfuron-methyl caused as much as 65% visible injury and reduced shoot dry weight, height and yield 64%, 41%, and 28%, respectively. This research concludes that acfluorfen, fomesafen, bentazon, imazethapyr and halosulfuron at the rates evaluated can cause the significant injury in adzuki bean.

Control of volunteer adzuki bean in soybean

The objective of this research was to evaluate the efficacy of various pre-emergence (PRE) and post-emergence (POST) herbicides for the control of volunteer adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) in soybean (Glycine max L.). Trials were conducted at two locations in 2005, 2006, 2007, and 2009. Experiments were arranged in a randomized complete block design with either five PRE or nine POST herbicides. Volunteer adzuki bean interference in soybean resulted in yield loss of up to 25%. Cloransulam-methyl, linuron, metribuzin, flumetsulam, and imazethapyr applied PRE provided up to 6, 24, 14, 8, and 0% control, respectively at 8 weeks after emergence (WAE), while acifluorfen, fomesafen, bentazon, thifensulfuron-methyl, cloransulam-methyl, imazethapyr, and imazethapyr plus bentazon applied POST provided 2, 2, 5, 34, 6, 4, and 12% control, respectively at 8 weeks after application (WAA). Generally, with the aforementioned herbicides, soybean yield was equivalent to the weedy control and soybean grain contamination with adzuki bean seed was consistently above the 1% maximum threshold. Chlorimuron-ethyl and glyphosate applied POST provided up to 84 and 94% visual control at 8 WAA, respectively, decreased adzuki bean density, biomass, and seed production, and generally decreased soybean contamination with adzuki bean below the 1% threshold. The only herbicides evaluated in this study that controlled volunteer adzuki bean in soybean were chlorimuron-ethyl (9 g ai.ha-1) and glyphosate (900 g ai.ha-1) applied POST. All the other PRE and POST herbicides evaluated did not provide adequate control of volunteer adzuki bean in soybean.

Glyphosate-Resistant Giant Ragweed(Ambrosia trifida L.)in Ontario:Dose Response and Control with Postemergence Herbicides

Giant ragweed (Ambrosia trifida L.) is competitive with agronomic crops and can cause significant yield losses. Rapid adoption of glyphosate-resistant (GR) crops and a concomitant increase in the reliance on glyphosate for weed management has led to the evolution of GR giant ragweed in Ontario, Canada. Field studies were conducted to evaluate the level of resistance in giant ragweed biotypes from Ontario, and to evaluate the effectiveness of various postemer-gence (POST) herbicides in soybean (Glycine max L.). The effective dose (ED) to provide 50%, 80% and 95% giant ragweed control was up to 1658, 9991 and >43200 g?a.e.?ha–1 4 weeks after application (WAA), respectively. For effective control, growers would need to apply glyphosate 18 times greater than the recommended field application dose. Glyphosate applied at the recommended field dose of 900 g?a.e.?ha–1 provided up to 57% control and resulted in soybean yield equivalent to the weedy check. Cloransulam-methyl applied POST provided up to 99% control, reduced giant ragweed density 98%, reduced giant ragweed shoot dry weight 99% and resulted in soybean yield equivalent to the weedfree check. Chlorimuron-ethyl, fomesafen, imazethapyr and imazethapyr plus bentazon applied alone or with glyphosate did not provide adequate control of GR giant ragweed. Based on these results, some GR giant ragweed biotypes from Ontario have evolved a high level of resistance to glyphosate. Cloransulam-methyl applied POST was the only herbicide that provided adequate control and suggests that additional weed management tactics will need to be implemented in order to effectively manage GR giant ragweed.

Safening effect of bentazon on cloransulam-methyl and halosulfuron-methyl in dry bean

Bentazon, applied as a tankmix, has been shown to have the potential for reducing the injury from some POST herbicides. Field experiments were conducted in 2008 and 2009 at Exeter, ON and in 2009 at Ridgetown, ON to determine if the addition of bentazon reduces the injury from cloransulam-methyl or halosulfuron-methyl applied POST in black, cranberry, kidney and white beans. Bentazon added to cloransulam-methyl reduced the level of injury 0 to 6% at 17.5 g·ai·ha–1 and 0 to 9% at 35 g·ai·ha–1 in dry bean. Bentazon added to halosulfuron-methyl reduced the level of injury as much as 4% at 35 g·ai·ha–1 and 6% at the 70 g·ai·ha–1. Bentazon added to cloransulam-methyl increased plant height as much as 3 cm. The addition of bentazon to halosulfuron-methyl had no effect on the height of various market classes of dry bean. Bentazon added to cloran-sulam-methyl generally has no effect on seed moisture content in black and white bean but decreased seed moisture content of cranberry and kidney bean as much as 4%. The addition of bentazon to halosulfuron-methyl caused no effect on seed moisture content of dry bean. Cloransulam-methyl caused a 7% to 18% reduction in dry bean yield compared to halosulfuron-methyl and 12% to 21% reduction in yield compared to bentazon. Bentazon added to cloransulam-methyl increased dry bean yield by 0.16 and 0.31 t·ha–1 at Exeter (2009) and Ridgetown (2009) respectively. The addition of bentazon to halosulfuron-methyl had no effect on dry bean yield.

Does the Application of a Fungicide after a Herbicide Reduce Soybean Injury and Increase Yield?

A total of four field experiments were conducted during 2017, 2019 and 2020 in Ontario, Canada to determine if applying a fungicide 2 - 3 days after a herbicide, applied POST, reduces visible injury, increases crop vigour and increases yield of soybean. At 3 DAB (days after fungicide application), the POST application of glyphosate, fomesafen, bentazon, thifensulfuron-methyl, cloransulam-methyl and imazethapyr caused 0, 11%, 5%, 18%, 9% and 12% visible injury in soybean, respectively. The injury decreased over time with less than 5% injury at 8 WAB (weeks after fungicide application) in all treatments evaluated. The application of pyraclostrobin/fluxapyroxad after the application of herbicides evaluated did not reduce soybean injury. Soybean vigour with glyphosate, fomesafen, bentazon, thifensulfuron-methyl, cloransulam-methyl and imazethapyr applied POST without the fungicide application was 100%, 91%, 95%, 84%, 91% and 88%, respectively at 3 DAB. The soybean vigour increased over time to 95% - 100% at 8 WAB. The application of pyraclostrobin/fluxapyroxad after the herbicide application did not improve soybean vigour, except with thifensulfuron-methyl where soybean vigour was improved 6% when followed by pyraclostrobin/fluxapyroxad. There was no effect of herbicide and fungicide treatments on soybean yield except for thifensulfuron-methyl and imazethapyr without the fungicide treatments which reduced soybean relative yield 7% and 10%, respectively. The application of pyraclostrobin/fluxapyroxad after the application of imazethapyr increased soybean yield 3%. Based on these results, applying pyraclostrobin/fluxapyroxad fungicide 2 - 3 days after glyphosate, fomesafen, bentazon and cloransulam-methyl does not affect soybean injury, vigour or yield, but it can slightly enhance the vigour and yield of soybean when applied after thifensulfuron-methyl and imazethapyr.

Expression of cytochrome P450 CYP81A6 in rice: tissue specificity, protein subcellular localization, and response to herbicide application

The cytochrome P450 gene CYP81A6 confers tolerance to bentazon and metsulfuron-methyl, two selective herbicides widely used for weed control in rice and wheat fields. Knockout mutants of CYP81A6 are highly susceptible to both herbicides. The present study aimed to characterize the CYP81A6 expression in rice. Quantitative real-time polymerase chain reaction（PCR） analyses demonstrated that foliar treatment of bentazon（500 mg/L） greatly induced expression of CYP81A6 in both wild-type（Jiazhe B） and its knockout mutant（Jiazhe m B）： a 10-fold increase at 9 h before returning to basal levels at 24 h in Jiazhe B, while in the mutant the expression level rose to 20-fold at 12 h and maintained at such high level up to 24 h post exposure. In contrast, metsulfuron-methyl（500 mg/L） treatment did not affect the expression of CYP81A6 in Jiazhe B within 80 h; thereafter the expression peaked at 120 h and returned gradually to basal levels by Day 6. We suggest that a metabolite of metsulfuron-methyl, 1H-2,3-benzothiazin-4-（3H）-one-2,2-dioxide, is likely to be responsible for inducing CYP81A6 expression, rather than the metsulfuronmethyl itself. Use of a promoter-GUS reporter construct（CYP81A6Pro：：GUS） demonstrated that CYP81A6 was constitutively expressed throughout the plant, with the highest expression in the upper surfaces of leaves. Subcellular localization studies in rice protoplasts showed that CYP81A6 was localized in the endoplasmic reticulum. These observations advance our understanding of CYP81A6 expression in rice, particularly its response to the two herbicides.

GIS based ArcPRZM-3 model for bentazon leaching towards groundwater

Groundwater contamination due to pesticide applications on agricultural lands is of great environmental concern. The mathematical models help to understand the mechanism of pesticide leaching in soils towards groundwater. We developed a user-friendly model called ArcPRZM-3 by integrating widely used Pesticide Root Zone Model version 3 （PRZM-3） using Visual Basic and Geographic Information System （GIS） based Avenue programming. ArcPRZM-3 could be used to simulate pesticide leaching towards groundwater with user-friendly input interfaces coupled with databases of crops, soils and pesticides. The outputs from ArcPRZM-3 could be visualized in user-friendly formats of tables, charts and maps. In this study we evaluated ArcPRZM-3 model by simulating bentazon leaching in soil towards groundwater. ArcPRZM-3 was applied to 37 sites in Woodruff County, Arkansas, USA to observe the daily average dissolved bentazon concentration for soybean, sorghum and rice at a depth of 1.8 m for a period of two years. Nineteen ranks of bentazon leaching potential were obtained using ArcPRZM-3 for all sites having different soil and crop combinations. ArcPRZM-3 simulation results for bentazon were compatible with the field monitored data in term of relative ranking and trend, although some uncertainties exist. This study indicated that macropore flow mechanism would be important in analyzing the effect of irrigation on groundwater contamination due to pesticides. Overall, ArcPRZM-3 could be used to simulate pesticide leaching towards groundwater more efficiently and effectively as compared to PRZM-3.