Studies On Seed Germination Conditions Of Red Sprangletop(Leptochloa Panicea(Retz.)Ohwi) And Screening Of Herbicides

Red sprangletop(Leptochloa panicea(Retz.)Ohwi)is one of annual weed in summer.However,in recent years,the occurrence of red sprangletop be found in rice field of the coasta area of Jiangsu Province,and red sprangletop is not control by cyhalofop-butyl.There are few resport on the red sprangletop up till now.In this paper,the dormancy and germination properties of red sprangletop were investigated.The influence of temperature,light,water potential,salt and pH on seed germination,and the influence of soil depth and soil moisture on germination emergence were studied.The sensitivity to different foliar-applied herbicides and soil-applied herbicides of red sprangletop was determined by pot experiment,and the single herbicide or compound herbicide on red sprangletop was screened.The ACCase CT domain of red sprangletop was amplified and sequenced to verify the relationship between the target-site mutation and the bad control effect of cyhalofop-butyl.Results were as followed:1.The research of germination and emergence of red sprangletopThe results of seed germination experiment indicated that red sprangletop seeds have not dormancy.The seeds could germinate under constant temperature between 20?40 ?,while the optimum temperature for germination was at 30 ? and the germination rate was 84.64%.Seeds can germinate over a wide range of temperature fluctuation,the temperature shift of 30/20,35/20,35/25 ?(L/D)was suitable for the seed germination,and the highest germination rate was 85.93%at 20/30 ?(L/D),optimum temperature shift.The seed could germinate without light,and there was 12%only in germination rate.The rate of germination increased with the increase of illumination time,and the top of germination happened under the photoperiod of 12 h/12 h(L/D).The seed germination was sensitive to water potential.It was more suitable for germination in the range of-0.2?0.0 MPa.However,the seed hardly germinated under the condition of less than-0.2 MPa water potential.The salt stress remarkably inhibited the seed germination and the germination rate was dropdown to 50.67%in 0.15 mol/L of salt concentration compared with 78.67%of the control treatment.There is no significant difference in seed germination rate under pH5-9.In the soil experiment,the seed emergence rate was the highest in the surface,and the seedling emergence was not observed when soil depth was more than 1.0 cm.The emergence rate is the highest in 25%soil moisture.2.Screening of herbicides for controlling red sprangletopThe efficacies of fifteen kinds of foliar-applied herbicides and eight kinds of soil-applied herbicides controlling red sprangletop was determined in pot experiment.The results indicated that the control effect of eight kinds of soil-applied herbicides on red sprangletop was all 100%,and those of 10 foliar-applied herbicides were lower control effect on red rprangletop.In the foliar-applied tests at 2-lesf,4-lesf and 6-lesf stage respectively,Metamifop and propanil were the most effective herbicides among the 15 kinds of herbicides.The efficacy of metamifop reached to 97,72%-100%at dose of 75-85 ml/667 m2 and that propanil was 78.85%-82.74%at dose of 1250-1500 ml/667m2 at 2-leaf stage of red rprangletop.The efficacy was 95.12%-97.18%at dose of 80-100 ml/667m2 of metamifop and that was 81.61%-86.76%at 1500-1875 ml/667m2 of the propanil in 4-leaf stage of red rprangletop.The efficacy was excellent at dose of 90-110 ml/667 m2 of Metamifop and 1500-2150 ml/667 m2 of the propanil applied at 6-leaf stage of red sprangletop.The combination of metamifop+propanil was screen and the efficacy reached all to 100%.The optimum formulating of metamifop vs propanil(1:25)was obtained by bioassay in 2-leaf.3.Gene sequence of ACCase CT domain of red sprangletopThe sequence of ACCase CT domain in red sprangletop was compared with Alopecurus myosuroides Huds.The results indicated that no mutation was in the sequence of red sprangletop at the seven amino acid substitutions reported in ACCase CT domain.It is sugested that red sprangletop did not produce target-site resistance to cyhalofop-butyl.