| Common diplachne(Diplachne fusca)is a noxious annual grass weed of paddy field in China.In recent years,it has been more serious in some paddy fields of coastal regions such as Hebei,Jiangsu province and Shanghai city.So far,there is still a lack of more research on the control of D.fusca,and the commonly used cyhalo fop-butyl has poor performance on it in practice.In order to provide theoretical reference for the scientific control and resistance management of D.fusca,as well as ensuring food safety,the contents were studed in this paper includes the optimum method to break the seed dormancy of D.fusca,and the effect of temperature,photoperiod,pH and other environmental factors on its germination and seedling emergence.Some traits of D.fusca were also investigated at maturation stage.The soil spray application and foliar spray application tests were conducted to determine the control efficacy of 19 herbicides for soil treatment and 14 herbicides for foliar treatment to D.fusca respectively.The resistance level of D.fusca to cyhalo fop-butyl and the cross-resistance of the cyhalofop-butyl-resistant D.fusca to three ACCase inhibitors was determined by the whole-plant dose-response experiments.Finally,the resistance mechanism of D.fusca to cyhalo fop-butyl was analyzed at a molecular level.Detailed results are as follows:The results indicated that the seed dormancy of D.fusca could be broken by paddy field stratification for 10 days,dryland stratification for 20 days and dry storage at room temperature for 60 days,and the germination rates were 80.11%,92.51%,96.24%respectively,while conditions for drying at low temperature was not conducive to breaking its dormancy.The seed dormancy of D.fusca was broken varying degrees by treatment with GA3 or warm water soaking,for example,500 mg/L GA3 soaking for 48h and water soaking at 55? for 12h could significantly increase the germination rate by 97.74%and 100%respectively.The optimum constant temperature for germination of D.fusca was at 35 ?,and the optimum alternate temperature for germination was at 35/20 ?(L/D);the highest germination rate was 75.77%under 24/0 h(L/D)photoperiod condition,while the germination rate under dark condition was only 10.73%;seeds could germinate at pH ranged from 4 to 10(more than 50%),and the germination rate were the highest from pH 6 to pH 8;seed germination was sensitive to water stress,under which the germination rate would be remarkablely decreased from 97.78%to 9.77%with the descending of water stress from 0 to-0.6 MPa;while it was tolerant to salinity,germination occurred even at 160 mmol/L NaCl(44.79%).Seedling emergence was highest when seeds were placed on the soil surface(72.22%),but no seedling emerged when seeds were buried in soil at depths of 0.3 cm or more;seedling emergence was highest(75.77%)when the soil water content was 50%,and it could not emerged when the soil water content decreased to 5%.The average plant height of D.fusca was 111.4cm,average productive tillering nodes were 3.2,average spike length was 25.7cm,average number of seeds per spike was 826,average weights of 1000-grain was 0.3288g,and the theoretical fruiting amount was 2643 per plant.The results of the herbicides screening test showed that 9 herbicides for soil treatment had significant effect on the control of D.fusca,of which the plant control efficacy(PCE)of pendimethalin,butralin,acetochlor,pretilachlor,butachlor,anilofos,oxyfluorfen and oxaziclomefone under the test dose could reach 100%.The PCE and fresh weight control efficacy(FWE)of pyraclonil under the test dose were more than 95%and more than 99%respectively.The control efficacy with metamifop,cyhalofop-butyl,florpyrauxifen-benzyl and propanil for foliar treatment at the 2-leaf,4-leaf and 6-leaf stage of D.fusca were all significantly better than other 10 herbicides.The PCE were obtained 100%at recommended high dose(80 ml/667m2)of metamifop at the 2-leaf,4-leaf and 6-leaf stage of D.fusca.The PCE were 100%,85.09%and 27.96%respectively with the recommended high dose(70 ml/667m2)of cyhalofop-butyl at the 2-leaf,4-leaf and 6-leaf stage,and the FWE were 100%,96.64%and 81.13%respectively.The PCE were 100%,59.47%and 77.78%respectively with propanil dose of 1500 ml/667m2 at the 2-leaf,4-leaf and 6-leaf stage,and the FWE were 100%,83.01%and 94.97%respectively.The PCE were 94.44%,88.21%and 66.26%respectively with the recommended high dose(80 ml/667m2)of florpyrauxifen-benzyl at the 2-leaf,4-leaf and 6-leaf stage,and the FWE were 97.38%,96.94%and 90.06%respectively.It has been confirmed that the 2-leaf stage was the optimun stage to control D.fusca,and for the 4-6 leaf stage of D.fusca,consideration should be given to the use of metamifop at the recommended high dose for control.The whole-plant dose-response experiments showed that the HH D.fusca population had evolved 8.9-fold resistance to cyhalofop-butyl compared with sensitive population.ACCase sequencing revealed that a point mutation(GGC to GCC)at amino acid position 2096,resulting in a Gly-2096-Ala substitution in the resistant population.In addition,the resistant D.fusca population(HH)with the Gly-2096-Ala mutation was cross-resistant to ACCase inhibitors such as metamifop(APPs),sethoxydim(CHDs)and pinoxaden(PPZ),and resistance index(RI)was 3.7,4.8 and 2.1,respectively. |
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