Control Technology Of Fenoxaprop-P-ethyl And Isoxadifen Ethyl Derivatives For Weedy Rice

With the growing area of direct seeding rice field in China,the harm of weedy rice is becoming more and more serious,and the weedy rice have become the third serious weed,the other two weed are barnyard grass and Chinese sprangletop,damaging cultivated rice growth.Owing to the extremely similar morphological features and physiological properties of weedy and cultivated rice,which also have the similar mechanism of absorption,transportion and metabolism of herbicides,it is generally difficult to control weedy rice in cultivated rice with post-emergence herbicides.On one hand fenoxaprop-P-ethyl has great control effect on grass weed,on the other hand it would easily cause serious phytotoxicity in cultivated rice.Isoxadifen ethyl,as an herbicide safener in maize and rice,can decrease the injury level to rice plants caused by fenoxaprop-P-ethyl.However,in the case of rice and weedy rice,it is difficult to apply isoxadifen ethyl at the same time in a manner that can safen cultivated rice but not weedy rice since they are extremely similar.Because isoxadifen ethyl will allow weedy rice to develop resistance to fenoxaprop-P-ethyl,it cannot be directly used on rice with the herbicide.Thus,it maybe practical for the safener to be applied directly to rice seeds before crop seeding to safen rice against post-emergence herbicides that would be lethal to both rice and weedy rice.This could enable selective weedy rice control without damaging cultivated rice.The experiment studied the control effect of fenoxaprop-P-ethyl on weedy rice and the safety of fenoxaprop-P-ethyl in cultivated rice,as well as the detoxification effect of the spraying and soaking treatments of isoxadifen ethyl in cultivated rice.To improve the seed treatment-based activity of isoxadifen ethyl,we modified its structure and generating a series of isoxadifen ethyl derivatives.To improve the biological activity of isoxadifen ethyl seed treatments,novel compounds were designed by splicing other groups,including amines,amino acids and 5-nitroguaiacol,to the parental structure of isoxadifen ethyl.The biological activities of the compounds were tested.In addition,the mechanism of fenoxaprop-P-ethyl relieving the damage in rice was explored preliminarily.The results are as follows:1.Fenoxaprop-P-ethyl provoked a significant decrease in the growth of weedy rice.Applied Fenoxaprop-P-ethyl at the dose of 200 ?mol/L,weedy rice stopped growing and died gradually.However it also had the poor selectivity at rice field.After 7 days of spraying Fenoxaprop-P-ethyl,the plant height selectivity index of it is 0.001 between weedy rice and cultivated rice and the fresh weight index is 0.0026.After 14 days of spraying Fenoxaprop-P-ethyl,the plant height selectivity index of it is 0.012 between weedy rice and cultivated rice and the fresh weight index is 0.032.Therefore,Fenoxaprop-P-ethyl easily caused serious phytotoxicity in cultivated rice.Spraying isoxadifen ethyl at certain dose could decrease the injury level effectively to rice plants caused by fenoxaprop-P-ethyl.Applied isoxadifen ethyl at the dose of 800 ?mol/L,the injury of cultivated rice was relieved most remarkably and the recovery rate of plant height and fresh weight are 70.83%and 76.94%,respectively.But the control effect of Fenoxaprop-P-ethyl in weedy rice appreciably reduced when isoxadifen ethyl was sprayed.Applied isoxadifen ethyl at the dose of 800 ?mol/L,the plant height control effect of Fenoxaprop-P-ethyl was decreased from 53.79%to 10.84%,and the fresh weight control effect from 58.43%to 12.54%.At the same time,thought the seed soaking experiment of isoxadifen ethyl,we discovered that the seed soaking treatment of isoxadifen ethyl did not relieve the injury level to rice plants caused by fenoxaprop-P-ethyl.2.Through hydrolysis and chlorination,the inactive compound,isoxadifen ethyl,was converted into the active acid chloride structure.Then,the acid chloride,as the intermediate,was spliced with other groups,including amines,amino acids and 5-nitroguaiacol,to obtain a series of isoxadifen ethyl derivatives and their structures were determined by mass spectrometry and 1H nuclear magnetic resonance spectroscopy.Isoxadifen ethyl derivatives were tested for its ability to decrease the injury in rice plants caused by fenoxaprop-P-ethyl.Compared with isoxadifen ethyl,compounds 2,4f,4g,4h and 4i showed similar recovery effects.Additionally,compounds 4a,4c,4d and 4e presented litter recovery effect as determined by recovery height among the derivatives,and compounds 4b showed the lowest performance levels and even caused injury to rice seedlings.In the seed soaking experiment,Compound 2 presented the greatest cultivated rice-protecting activities among the derivatives,as weell compound 4g and 4h presented the greater activities.However,compounds 4b,4d,4e,4f and 4i presented a few rice-protecting activities,compounds 4a and 4c showed the lowest performance levels in addition.3.In the experiment,we discovered that there were generally no significant differences between seed soaking treatment by isoxadifen ethyl(IE)and water at the same dose of fenoxaprop-P-ethyl treatment for the GST,CAT,POD,SOD activities and GSH,MDA contant of cultivated rice.However,comparing with seed soaking treatment by water,the GST,CAT,POD,SOD activities and GSH contant increased obviously on seed soaking treatment by isoxadifen ethyl derivatives(IH and IA)at the same dose of fenoxaprop-P-ethyl treatment,and the MDA contant decreased obviously.