Sensitivity Differences Of Different Rice To Imazamox And The Development Of Protective Agent

Direct seeding of rice is easy to breed weeds and weedy rice,which seriously affects the growth of rice and the final yield.The use of herbicides can effectively control weeds,but is not an effective treatment for weedy rice which is closely related to cultivated rice,but is not an effective treatment for weedy rice which is closely related to cultivated rice.Hopefully,the development and extension of herbicide-resistant rice can solve this problem.Imazamox is an inhibitor of acetolactate synthetase(ALS),which belongs to the imidazolinone herbicide.Mutations in ALS gene will affect the binding of ALS protein to imidazolinone herbicides,thus making rice resistant to imidazolinone herbicides.At the same time,the improper application of herbicide will not only inhibit the growth of herbicide-resistant rice,but also cause damage to the sensitive rice varieties around it.Improper application mainly includes herbicide concentration,rice growth period and external environmental factors of herbicide application.Therefore,to develop effective protective agent of imazamox and the application condition of it is particularly important.At first,different rice varieties/strains with and without ALS mutation were selected as materials to select rice varieties/lines with different resistance to imazamox and the corresponding working concentration,which was taken as the research material.Then three amino acids(valine,leucine,and isoleucine)were mixed as protective agent A.On this basis,brassinolide,which has a broad spectrum effect on plant growth and resistance,was added as protective agent B.The degree of damage caused by imazamox to rice and the repair effect of protective agent were compared under different temperatures and leaf ages.Finally,the effects of protective agent on the growth,antioxidant enzyme,detoxification enzyme and ALS enzyme activities,as well as the expression levels of ALS,P450 and GST related genes in different rice varieties/strains treated with imazamox were determined,in order to reveal the mechanism of protective agent A and B in alleviating the imazamox damage of different rice varieties/strains.The main research results are as follows:1.Rice plants at the four-leaf stage were treated with different concentrations of imazamox,and then the effects of herbicide treatment for 12 days on plant growth of Nanjing 9108(sensitive rice: without ALS mutation)and Jinjing 818,73119,K37(resistant rice: with defferent ALS mutation)were studied.The results showed that the survival rate was less than 50.0%,and the growth of Nanjing 9108 was greatly inhibited when the concentration of imazamox was greater than 0.6 times of the action concentration.The resistant variety Jinjing 818 was still resistant at 7 times of the action concentration of imazamox.The survival rate of 73119 and K37 rice was less than 50.0% when treated respectively with more than 5 times and 3 times of the action concentration.It can be seen that rice materials with different ALS mutation sites are all resistant to imazamox,but the degree of resistance differed among cultivars.Therefore,in this study,0.6 times and 3times of the action concentration of imazamox were used as screening concentration for the development of protective agent for sensitive and resistant rice.2.Nanjing 9108,a sensitive variety,and K37,a resistant strain,were used as materials to analyze the effects of imazamox and protective agent on the growth characteristics of different rice varieties at different external temperatures and leaf ages.The results show that the protective agent A and B had significant repair effect on herbicide damage of two kinds of rice under the optimum temperature at the four-leaf stage.However,high temperature increased the toxicity of imazamox to rice,and protective agent A and protective agent B had poor repair effect on it.When rice reached the five-leaf stage,there was no obvious damage to sensitive and resistant varieties of rice,and the growth of rice were not affected by the treatment of protectant.Therefore,the rational use of herbicide protective agent should not only relate to the growth period of rice,but also relate to the external environmental conditions,especially the air temperature at the time of application.3.In the experiment on the physiological mechanism of protective agent A and B alleviating the imazamox damage of different varieties of rice,the research found that:protective agent A and B could alleviate the inhibition effect of imazamox on plant height,root length and biomass of sensitive and resistant rice varieties,and increase the chlorophyll content in rice leaves.Protective agents A and B could increase the activities of antioxidant enzymes in rice,accelerate the scavenging of active oxygen in rice,and induce the activity of cytochrome P450 in rice leaves to promote the metabolism of herbicides,but the two protective agents had no effect on GST activity.Protective agents A and B increased the expression of CYP81A6,but there was no significant difference between this treatment of Os GSTU2 and imazamox treatment.The results of target enzyme ALS activity showed that the inhibition rate of ALS activity of sensitive varieties was significantly higher than that of resistant varieties,but protective agents A and B could effectively alleviate the inhibition of ALS enzyme of sensitive varieties,but had no significant effect on ALS of resistant varieties.Imazamox treatment could significantly up-regulate the expression of ALS gene in rice,but there was no significant difference between protective agent treatment and imazamox treatment.To sum up,this study determined the safe application concentration of imazamox on sensitive and resistant varieties.It was also confirmed that the protective agents selected in this study could repair the damage of different varieties of rice caused by imazamox during the four-leaf stage after 5 days of herbicide treatment,and the effect of protective agent B was better than that of protective agent A.