| Rice is one of the important grain crops and it plays an important role in agricultural production in China.However,weeds are an important factors affecting the yield and quality of rice.In recent years,with the large-scale promotion of agricultural mechanization and the transfer of rural labor force to cities,Direct-seeded are being promoted on a large scale which are represented light cultivation methods,but the chemical control of weeds faces two major problems in direct-seeded paddy field.Firstly,there are many weed species with high occurrence density,among which Echinochloa crusgalli and Leptochloa chinensis are dominant on annual gramineous weeds,and dryland weeds such as Digitaria sanguinalis are also spreading to rice fields,which makes the current conventional herbicide difficult to control weed.Secondely,herbicde resistance in weeds in paddy fields is a widespresd problem,especially in acetolactate synthase(ALS)and acetyl Co A carboxylase(ACCase)inhibitors,as well as synthetic auxins herbicides,which often leads to the failure of weed control..In view of the above problems,it is of great significance to develop efficient and safe new herbicides.NC1 is a new compound,and there are no report on its herbicidal activity,crop safety and mechanism of action.In order to clarify whether NC1 can be used in paddy fields,this paper studies the herbicidal activity,suitable application period and rice safety in paddy fields,then a field trials were performed.At the same time,the mechanism of action and selective principle of NC1 were studied.The following results and conclusions were obtained from the above experiments:The whole-plant bioassay was used to determine the herbicidal effect of common gramineous weeds(E.crusgalli,L.chinensis and D.sanguinalis)to NC1 in paddy field.The results revealed that as a pre-emergence herbicide with the dose of 30 g a.i./ha,the inhibitory rate of NC1 to sensitivity and resistance annual gramineous weeds were all above93.26% and Its ED90 ranged from 4.56 to 26.41 g a.i./ha.When treating by foliar treatment at the 2.5~3.5 leaf stage of weeds with the dose of 144 g a.i./ha,the inhibitory rate of NC1 to sensitive Echinochloa spp.and Mefenacet-resistant E.crusgalli var.crusgalli were all above 90.57%,but slightly lower on L.chinensis,D.sanguinalis,Penoxsulam-resistant Echinochloa spp.and Quinclorac-resistant E.crusgalli var.zelayensis.Field test results showed that as a pre-emergence herbicide at the dose from 60 to 75 g a.i./ha,the control efficacy of E.crusgalli and L.chinensis were both higher than 92.47%,when treating by early foliar treatment at the 1~2 leaf stage of weeds with the dose from 100 to 112.5 g a.i./ha,the control efficacy of E.crusgalli and L.chinensis were both higher than 96.68%.Therefore,based on the results of whole-plant bioassay and field experiments,NC1 is suitable for soil treatment or treating by early foliar treatment at the 1~2 leaf stage of weeds to control gramineous weeds in paddy fields.The whole-plant bioassay was used to determine the safety of applying NC1 to rice(indica ‘Hanyou 73’,japonica ‘Xudao 9’ and glutinous ‘Dahua 1’)in dry direct-seeded,water direct-seeded and different leaf stage.The results showed that the selectivity index of NC1 as a pre-emergence to three different types of rice and gramineous weeds was 4.12 to27.82 in dry direct-seeded,the selectivity index of NC1 as a pre-emergence to three different types of rice and gramineous weeds was 4.42 to 34.63 in water direct-seeded.When treating by foliar treatment at the 2.5 and 3.5 leaf stage of rice with the dose from 9to 288 g a.i./ha,there was no significant difference in the fresh weight each treatment.When treating by foliar treatment at the 1.5 leaf stage of rice with the dose from 9 to 144 g a.i./ha,there was no significant difference in the fresh weight each treatment,but at the dose of 288 g a.i /ha,the inhibition rates of indica,japonica and glutinous were 7.80%,7.48% and 5.01%.Based on the safety of NC1 for dry direct-seeded,water direct-seeded and rice with different leaf ages,the safety of NC1 for three different types of rice were glutinous > japonica > indica.In order to further expand the herbicidal spectrum,NC1 was mixed with Benzosulfuron-methyl,Halosulfuron methyl and Pyraclonil which were commonly used in paddy fields.The results showed that the component of NC1 and Benzosulfuron-methyl(1.5:1)at the dose from 100 to 120 g a.i./ha,it had a good inhibitory effect to resistant gramineous,some broadleaf and nutsedge weeds,and it had a good safety to rice.The component of NC1 and Halosulfuron methyl(1:1)at the dose from 100 to 120 g a.i./ha,it had a good inhibitory effect to resistant gramineous,some broadleaf and nutsedge weeds,but with the increase of the dose of chlorpyrisulfuron,the compound has a significant inhibitory effect on rice.The component of NC1 and Pyraclonil(1:3)at the dose from 160 to 200 g a.i./ha,it had a good inhibitory effect to resistant gramineous,broadleaf and nutsedge weeds,and it had a good safety to rice.In order to clarify the mechanism of action of NC1,with E.crusgalli as the research object,the activity of α-amylase and ALS of E.crusgalli were measured after NC1 treatment,Pretilachlor and Penoxsulam were used as control agents.The results showed the activity of α-amylase E.crusgalli were all lower than without treatment at all time periods,and it showed the same inhibitory effect as the control agents Pretilachlor.The ALS activity of E.crusgalli decreased with the increase of NC1 concentration,and it showed the same inhibitory effect as that of the control agent Penoxsulam.Therefore,it is speculated that NC1 has a similar mechanism of action with amide and ALS inhibitor herbicides.In order to clarify the selectivity principle of NC1,the activity of α-amylase,ALS and GSTs in E.crusgalli and rice.The results showed that the α-amylase activity of the E.crusgalli at a certain concentration of NC1 was lower than that of untreated treatment at 1 d,3 d and 5 d after treatment,Under the treatment of NC1 α-amylase activity of rice was lower than that of untreated treatment,but α-amylase activity was significantly higher than that of untreated treatment at 5 d.The activity of ALS in vitro of E.crusgalli and rice was inhibited,but the IC50 of rice(the concentration of 50% agent to inhibit ALS activity)was13.58 times that of E.crusgalli.Under NC1 treatment,the activity of GSTs in rice was significantly higher than that without treatment at all time periods,while the GSTs in E.crusgalli increased slightly at 6h after treatment,while the GSTs in E.crusgalli at 24 h,72 h and 120 h after treatment were all lower than that without treatment.Therefore,it was speculated that NC1 had different effects on α-amylase,ALS and GSTs activity during germination of E.crusgalli and rice,which was an important selectivity principle of NC1 between rice and weeds.In conclusion,1 NC1 can be used to control gramineous weeds in direct-seeded paddy fields and it is safe for rice,it can be used as a ideal agent for the management of resistant weeds in paddy fields.2 Three new compounds mixed with NC1 have been screened out,it can be further verified in the field.3 The mechanism of action and selectivity principle of NC1 had been preliminarily clarified,It provides a direction for the further study of the mechanism of action. |
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