Study On Safety And Mixed Effects Of Florpyrauxifen On Different Rice Varieties

Florpyrauxifen is a novel aryl picolinate herbicide registered by Dow Agro Sciences in 2016 and listed in China in 2018.It can effectively control gramineous weeds,broad-leaf weeds and cyperaceae weeds.The application of florpyrauxifen in rice production will lead to dwarfing and stagnant green in some rice varieties,and serious phytotoxicity will lead to reduction of rice yield.Therefore,it is particularly important to clarify the sensitivity of to different rice varieties.In this experiment,32 rice varieties in northeastern China were selected as the research objects,and the sensitivity of florpyrauxifen to different rice varieties was determined by whole-plant bioassay.The reasons for the difference in sensitivity of different rice varieties to florpyrauxifen were analyzed and the mixing effect and optimum mixing ratio of florpyrauxifen with penoxsulam and bentazon were determined.The study results are as follows:1.Safety of florpyrauxifen in different rice varietiesSensitivity of rice at different leaf ages to florpyrauxifen was different.When florpyrauxifen was applied at 2-3 leaf stage,20 of 32 rice varieties were sensitive.When it was applied at 3-4 leaf stage,9 of 32 rice varieties were sensitive.Among Heilongjiang rice varieties,Songjing 22,Suijing 4 and Longjing 47 were sensitive to florpyrauxifen at 2-3 leaf stage,but not sensitive at 3-4 leaf stage.Among Jilin rice varieties,Tiejing 11,Tongke 27,Jinian 6,Yanjing 26 and Songliao 5 were sensitive to florpyrauxifen at 2-3 leaf stage,but not sensitive at 3-4 leaf stage,while Jinian 10 was sensitive to high concentration of florpyrauxifen at 2-3 leaf stage,and sensitive to all doses at 3-4 leaf stage.Among Liaoning rice varieties,Shendao 9,Liaojing 390,Fuhe 66,Tiejing 13 and Longjing 772 were sensitive to florpyrauxifen at 2-3 leaf stage,but not sensitive at 3-4 leaf stage.Overall,the higher the leaf age of rice,the lower the sensitivity to florpyrauxifen.The effects of on plant hight,tillers and yield of rice varieties were also different.Florpyrauxifen could reduce plant height,panicle weight,spikelets per panicle,number of mature grains per panicle and yield of sensitive rice varieties.It had little effect on seed setting percentage,tiller,number of panicles and 1000-grain weight of rice,but had little effect on yield of insensitive rice varieties.It can be concluded that florpyrauxifen affects rice yield by inhibiting plant height,panicle weight,spikelets per panicle,number of mature grains per panicle of sensitive rice varieties.2.Effects of florpyrauxifen on physiology and biochemistry of riceThe sensitive variety Shendao 11 and the insensitive variety Jiudao 60 were used to apply 30 g ai/ha of florpyrauxifen in the 3-4 leaf stage.The influence of chlorophyll content,MDA content and protection enzyme and GSTs activity of the two rice varieties in different days are as follows:After treatment,the decrease of chlorophyll content in Shen Dao 11 was more obvious than that in Jiudao 60,and it took longer for She n Dao 11 to return to normal level.The content of MDA in Shen Dao 11 increased more than Jiudao 60 after treatment.Excessive accumulation of MDA could cause damage to Shen Dao 11.Jiudao 60 could alleviate membrane lipid peroxidation faster,eliminate MD A in vivo and avoid injury.SOD activity in both rice varieties decreased first and then increased after application,but SOD activity in Jiudao 60 could recover to normal level 7 days after application,and Shendao 11 could not recover within 7 days after application.POD activity in both rice varieties was different and increased significantly after application of pesticides,but POD activity in Jiudao 60 could recover to normal level 7 days after application.The POD activity in Shen Dao 11 increased wit hin 7 days after application,but could not be restored to normal level.The CAT activity in Jiudao 60 decreased first,then increased and then decreased,and returned to normal level on the 7th day after application,while the CAT activity in Shen Dao 11 increased first and then decreased.The CAT activity in treatment group was lower than that in control group on the 7th day after application.The activity of GSTs in Jiudao60 increased and showed a bimodal trend after application.The activity of GSTs in Jiudao60 recovered to normal level 7 days after application.The activity of GSTs in Shendao 11 also increased after application,but it was still significantly higher than the control level 7 days after application.3.The mixture of florpyrauxifen and penoxsulam has synergistic effect in controlling Echinochloa crusgalli.When penoxsulam and florpyrauxifen were mixed at the dosage of 8.90+12.56 g a.i./ha,Echinochloa crusgalli could be effectively controlled.The optimum mixing ratio was 1:1.4.The mixture of florpyrauxifen and bentazon has synergistic effect in controlling S.juncoides Roxb.When florpyrauxifen and bentazon were mixed at the dosage of 16.44+741.46 g a.i./ha,S.juncoides Roxb could be effectively controlled.The optimum mixing ratio was 1 :48.1.