| As the production of agricultural modernization,herbicide possesses the function of killing the weeds effectively,and lowering the labor costs.Bensulfuron-mehtyl(BSM),which is an important member of sulfonylurea herbicide class and widely applied in paddy fields owing to its high efficiency,low toxicity and safety.However,in many crop-rotation fields in Fujian Province,the residue of herbicides e.g.BSM in paddy soils bring severe hazards to the sensitive crops such as Nicotiana tabacum planting later.Few studies pay attention to indirect effects brought by sensitive crops under the residue of BSM such as the of resistance to important pests and pathogens,and these studies lack of timeliness.In addition,the physiological alterations based on anti-pests/pathogens,such as the change of jasmonic acid(JA)/salicylic acid(SA)levels was not reported in limited studies.The methods of plant-remedy are of limitation.We try to investigate the resistance to pests and pathogens of plants under the treatment of BSM,and discover the physiological factors including JA/SA based on the altered resistance in our study.We also use JA and SA as plant regulators used on the BSM-treated plants and determine the reactions.First of all,we made an investigation on the herbicides applied in Fujian Province and the situation of tobaccos affected by the herbicide of improper utilization.Among the herbicide causing potential hazards on tobacco production in Fujian,only the amount of BSM for utilization was keeping fast rising in recent years The damage of tobaccos occurred in some fields caused indirectly by herbicides mainly used in paddy soils previously,and these herbicides were mainly BSM and compounds mixed with BSM and quinclorac,or other herbicides.Thus we determined BSM as the object in our further studies.The hazards brought by different dosage of BSM applied in the soil was investigated.This program chose the gradient concentration of 2.0 mg·kg-1,1.0 mg·kg-1,0.25 mg·kg-1,0.1 mg·kg-1,0.05 mg·kg-1 and 0 mg·kg-1(CK)to treat tobaccos in order to mimic the residue in the fields.The correlated symptom caused by herbicide emerged about 2 d post herbicide treatment,but was different on susceptible plants according to the herbicide dosage.We finally chose the dosage of 0.25 mg·kg-1 and the timepoint of 10 d post treatment in our further study.We also identified that the length and width of leaves were inhibited under this condition.How does BSM affected the resistance to pests and pathogens of susceptible plants?It was found that the density of adult Bemisia tabaci feeding on BSM-treatedplants was smaller than the one on control plants 15 d later.post infestation.But the density of eggs deposited by adult B.tabaci showed no significant difference.Myzus persicae was fed on leaves of BSM-treated and control plants then it was discovered that the longevity of each stage of bodies,and the life of insects,as well as the fecundity were not significantly affected when insects were feeding on BSM-treated tobacco leaves.In the Tobacco mosaic virus(TMV)assay,both BSM-treated and control plants were inoculated with viruses.The phenotype of N.tabacum was assessed and it was found that the level of the symptom on herbicide-treated plants significantly lower than control ones 10d post virus-inoculation.Similarly,virus-induced symptom on lobus cardiacus under the treatment of BSM showed milder than the ones of without herbicide.But it was more serious 15 d and 20 d post virus-inoculation.The relative amount of virus by RT-qPCR was determined and it was discovered that the amount of virus in BSM-treated plants showed remarkable lower 10 d post virus-inoculation but significantly higher than that of control plants another 10 d later.This was correlated to our phenotype-observation.The fluctuation of accumulation of virus in plants under low-concentration of BSM was much slighter,which indicated that the activity of viruses was affected by the level of symptom caused by herbicide.The contents of(jasmonic acid/salicylic acid)JA/SA was determined based on the resistance to pests and viruses of plants under the treatment of BSM.We tried the method of RT-qPCR and LC-MS in order to determine the expression of marker genes related to the pathway and the contents of relative phytohormones,respectively.The expression of WIPK in JA signaling,as well as PR la and PAL in SA signaling,showed remarkable up-regulation under the treatment of herbicide.Then we determined the expression of PR l a and PAL at the time point of significant difference of virus amount and found that it was inhibited compared to plants without herbicide 10 d post inoculation.Thus indicated that the biosynthesis of SA was blocked in BSM-treated plants which provided suitable space for the explosive multiplication of viruses.We determined the expression of RDR1 and RDR6 at several time points before or after TMV inoculation because RDR family can be mediated by SA and play key role in regulation of anti-virus in plants.The result showed that the expression of both RDR1 and RDR6 was significantly affected in the later time post TMV-inoculation while the former was inhibited and the latter was inducedHow do JA/SA and there inhibitors diethyldithiocarbamic acid(DIECA)/salicylhydroxamic acid(SHAM)act on BSM-treated plants based on the results of previous research?It was found that the symptoms caused by herbicides couldn’t be suppressed by chemicals we used,and the time of symptom-emergency was similar among each groups.However,we discovered that single application of JA/SA showed positive regulation to the growth of plants,and SA performed better,while the mixture of DIECA/SHAM caused negative impact on the plants.In SA-deficiency mutant Arabidopsis thaliana assay,it was confirmed that plants could be more sensitive to herbicide owing to the lower content of SA.We increase the frequency of SA application solely and discovered that there was still no remarkable improvement of plants growth under the treatment of BSM.Then the expression of genes related to the anti-oxidative stress in plants was determined under higher-frequency application of SA.SA improved the level of reactive oxygen species(ROS)level in BSM-treated plants,and also improve the expression of both SOD and APX,but inhibit the activity of CAT and POD 10 d post herbicide treatment.However,when it came to the time point of 20 d post BSM-treatment,SA caused no significant impact on ROS scavenging in plants,and it only inhibited the activity of POD in BSM-treated tobaccos.This was correlated to the 3,3’-diaminobenzidine(DAB)/nitrotetrazolium blue chloride(NBT)staining assays.SA similar had no impact on ROS level in plants without herbicide,but can improved the activity of POD and CAT,also we cannot tell whether it can bring influence on the quality of tobaccos.This subject based on the practical production and investigate the damage brought by the residue pf BSM in the soil,as well as the resistance to pests and viruses indirectly affected by herbicide.Then the fundamental physiological responses based on the pest/viruses resistance was discovered,and the impact brought by the application of plant regulators based on the physiological phenomenon was also investigated.This study reflected the problem brought by residue of herbicide from another aspect,and provided the potential settlement to this problem. |
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