Research On Preliminary Mechanism Of Resistance To Tobacco Bacterial Wilt Induced By Fulvic Acid

Tobacco Bacterial Wilt is a soil-borne bacterial disease caused by Ralstonia solanacearum,which leads to immeasurable damage to tobacco production every year in China,and causes lots of losses to tobacco farmers.The control effect could hardly meet expectations for the characteristics of the pathogen,occurrence characteristics,host resistance and other factors.No matter agricultural chemicals or biological control technology does little effect.It has become an important subject that exploring new method to control Tobacco Bacterial Wilt.At present,the tobacco plant resistance induction and tobacco root micro-ecological research have shown good prospects of application.Fulvic Acid,as a new type of resistance induction material,is widely sourced and easy to obtain.It has shown some effect on various crops to control fungal diseases,but the study on tobacco bacterial wilt has not been carried out.Therefore,through indoor and field tests,this study analyzed the effects of antiseptic,tobacco growth,tobacco resistance enzyme activity testing,tobacco strain resistance gene testing,tobacco root micro-ecology,and cyandisease.The effect of fulvic acid on Ralstonia solanacearum,tobacco growth,disease-control and mechanism are clarified,and the main results are as follows:1.Study on the biological activity of Fulvic Acid on Ralstonia solanacearum and growth of tobacco.This experiment used the classic Oxford Cup method to compare the size of the antidote ring produced by different concentrations of fulvic acid to the Ralstonia solanacearum.The results showed that the antidote of fulvic acid was 0cm in the concentration range of 0.001mmol/L ~30mmol/L.It was shown that fulvic acid had no inhibition effect on the growth of Ralstonia solanacearum.Through the indoor medicine seed germination test,it was found that 1mmol/L fulvic acid treatment can shorten the time required for tobacco seed germination about 12 h,and 1mmol/L fulvic acid treatment can make tobacco seed germination rate reach 97%,higher than control treatment by 4 percentage,and the germination index reached 83,much higher than the control treatment 59.11.The fulvic acid treatment of 0.01mmol/L,0.1mmol/L,10mmol/L and 30mmol/L also increased the germination index of tobacco seeds to varying degrees.The results of the potted plants found that the foliar application of fulvic acid with 1mmol/L,10 mmol/L and 30mmol/L can significantly increase the aboveground weight of tobacco.And the 1mmol/L FA foliar application's promotion is the most obvious.1mmol/L fulvic acid treatment also has a significant boost effect on the fresh weight of the root,while 1mmol/L,10 mmol/L and 30mmol/L fulvic acid are also significantly improved by irrigation treatment and can significantly improve the root fresh weight and root dry weight of the root of tobacco.2.Study on the control effect of tobacco bacterial wilt disease induced by Fulvic Acid.Through indoor potted tests,it was found that the irrigation treatment cannot offer a high control effect,and there was no significant difference between different concentrations(P< 0.05),while the foliar application of fulvic acid at different concentrations are able to lowering the disease index and have a certain control effect of which the highest relative control effect was the foliar application of 10mmol/L fulvic acid,reaching 35.69%.While the relative control effect decreased to a certain extent when the application concentration was higher or lower than 10mmol/L.The results showed that the control effect of fulvic acid was slightly lower than 2,6-dichloro-isonicotinic acid and higher than benzothiadiazole,and the resistance to tobacco bacterial wilt induced by fulvic acid was much higher than that of salicylic acid.3.Study on the mechanism of resistance to tobacco bacterial wilt induced by Fulvic Acid.Through the detection of several defensive enzymes of tobacco leaves in 1d-5d after treatment,it was found that fulvic acid can increase the activity of POD,SOD,PAL and PPO in the tobacco leaves to 2.012,1.364,2.75 and 1.574 times than the control treament.Among them,the activity of fulvic acid to phenylalanine ammonialyase is the most significant,indicating that fulvic acid plays an important role on the promotion of phenylalanine ammonialyase metabolism rate in tobacco.Results on the expression of defense genes in different pathways of tobacco found that fulvic acid can not only increase the relative expression of the PR2 and PR1/c genes of salicylic acid pathways to increase the resistance to tobacco bacterial wilt disease,but also increase the overexpression of the ethylene channel gene NtACC Oxidase and the the ubiquitin-proteasome system enzyme gene NTRNF-217.And NtACC Oxidase and NtRNF-217 may play a more critical role.4.Field control effect of fulvic acid on tobacco bacterial wilt disease.Field test set 1mmol/L FA,10mmol/L FA,30mmol/L FA,0.25mmol/L INA,0.5mmol/L SA,1mmol/L BTH and blank control for a total of 7 treatments,applied by foliar at quasi-rosette stage of tobacco,three times every 7 days after the first time.The results showed that the foliar application of 10mmol/L and 30mmol/L of fulvic acid can increase the height,the maximum leaf length and width in rosette atage and increase stem circumference and the maximum leaf length.And 10mmol/L of fulvic acid foliar application has good control effect on tobacco bacterial wilt after 60 d of application,reaching 35.64%,lower than 0.25mmol/L INA treatment and higher than 1 mmol/L BTH treatment.