Study On Measures Of Mitigating Tobacco Atrazine And Mesotrione Phytotoxicity

In most dry farming tobacco areas in China,corn and flue-cured tobacco are often planted adjacent to each other in the field.When spraying herbicides in corn fields,many factors can cause the herbicides to drift,thereby triggering tobacco damage to adjacent plots.With the extensive use of herbicides in corn fields,the tobacco damage caused by the drift of herbicides in corn fields has become a problem that cannot be ignored in tobacco leaf production.To this end,this paper uses the main tobacco varieties as experimental materials,and carried out relevant experimental studies on two herbicides atrazine and mesotrione,which are commonly used in corn fields.Screen out the relieving agent with significant relieving effect and suitable for tobacco and explore the best application time.By measuring the effect of different relieving agents on the content of malondialdehyde(MDA)and glutathione(GSH)in tobacco plants,explored the mechanism of action of relieving agents to alleviate the herbicide toxicity of tobacco herbicides,explored the differences in the number of culturable microorganisms on tobacco leaves with different drug resistance levels,and selected bacterial strains with certain resistance.1.Screen of the moderator mitigating tobacco herbicide phytotoxicity drifted from cornfield and decision of optimal application timeThe main planted flue-cured tobacco variety Yunyan 87 was used as the test material.Six commonly used moderators were used as test agents.Screening of atrazine and mesotrione moderators and an investigation of the optimal application time,in order to screen out those with significant mitigating effects and determine the optimal application time.The results of different application times of Zhiliyuan,Yepukang and Brassinolide showed that to mitigate drift herbicide phytotoxicity of atrazine and mesotrione to tobacco the best applying time of Zhiliyuan and Yepukang were 5 to 7 days before the herbicide used in cornfield,with the mitigating effects from 66.46% to 78.61%.And the best applying time of Brassinolide was 1 to 3 days after the herbicide used in cornfield,with the mitigating effects from 67.81% to 68.01%,which can effectively prevent and mitigate the herbicide phytotoxicity.2.Effects of different moderator treatments on MDA and GSH content in tobacco plantsBy measuring the changes of MDA and GSH content in tobacco,the mechanism of alleviating the effects of 6 moderators on herbicide damage in corn fields was explored.The results of this study found that,compared with the control of fresh water,the corn field herbicides atrazine and mesotrione treated tobacco with stems and leaves increased the MDA content and the GSH content in tobacco significantly.In the atrazine mitigation test,the content of malondialdehyde in leaves of tobacco plants treated with YePukang,Zhiliyuan before and Brassinolide was significantly lower than that of atrazine,Which are55.54%,62.36%,and 55.32% lower,respectively,and the content of reduced glutathione is significantly higher than that of atrazine control,which are 73.17%,95.12%,and 70.73% higher;In the mesotrione mitigation test,the content of malondialdehyde in leaves of tobacco plants treated with Yepukang,Zhiliyuan before and after Brassinolide was significantly lower than that of mesotrione in the control group,which were 56.44%,58.86%,and 54.80% lower,respectively.The content of reducedglutathione was significantly higher than that of mesotrione control,which were 68.29%,68.29%,and65.85% higher.This is consistent with the screening of atrazine and mesotrione moderators and the results of exploring the optimal application time,which indicates that the moderators may alleviate the toxicity of tobacco plant herbicides by participating in the antioxidant response of tobacco plants.3.Studies on foliar microorganisms of tobacco varieties with different herbicide tolerance levels and screening of herbicide resistant bacteria strainsThe number of foliar microorganisms in different resistant tobacco varieties at different periods was compared by the plate coating method,and drug-resistant bacteria strains were screened by the toxic media method.The test results showed that there were significant differences in the number of cultivable foliar microorganisms in tobacco varieties with different tolerance levels to the two cornfield herbicides atrazine and mesotrione,community structure is bacteria> actinomycetes> fungi.During the peak period when the number of bacteria is dominant,the number of bacteria in highly resistant varieties and moderately resistant varieties is significantly higher than that in highly sensitive varieties.It is speculated that there may be dominant bacterial strains with mitigation effects on highly resistant varieties,which can alleviate tobacco toxicities caused by herbicide drift.Five drug-resistant bacterial strains were further isolated from the leaves of highly resistant tobacco varieties,all of which belong to the Bacillus bacterial and showed high resistance to two cornfield herbicides.These drug-resistant strains may have played a positive role in resistance to tobacco varieties.Among the 6 kinds of moderators,Zhiliyuan,Yepukang and Brassinolide have better mitigating effects.The best application time of Zhiliyuan and Yepukang was 5 days before spraying the herbicide,and the best application time of Brassinolide was 1 day after spraying the herbicide;the content of MDA and GSH in tobacco plants treated with different relieving agents is significantly different.It is speculated that the relieving agent may alleviate the toxicity of tobacco herbicides by participating in the antioxidant reaction in tobacco plants;tobacco varieties with different tolerance levels of corn field herbicides have significant differences in the number of culturable microorganisms on the leaf surface.The overall structure of the community is bacteria> actinomycetes> fungi.Five drug-resistant bacterial strains were isolated,all of which belonged to Bacillus bacteria.