| Peanut?Arachis hypogaea L.?is one of the important oil and economic crops in China.In recent years,with the adjustment of the industrial structure of the agricultural supply side,the planting area of ??peanuts has continuously increased,and the degree of disease damage in the peanut leaf sector has been increasing year by year.At present,the main method for controlling peanut leaf spot diseases in production is spraying fungicides.However,chemical control methods may be lead to increase the use of pesticides,the resistance of pathogens,serious environmental pollution and other issues.As a safe and effective disease control measure,plant induced resistance has a broad application prospect in the control of peanut leaf spot diseases.Therefore,in this paper,the inducer?calcium chloride?with good induction effect on peanut web blotch and early leaf spot disease were screened from 6 different inducers through field experiments.At the same time,potted test was used to study induce peanut resistance to web blotch disease,the organizational structure resistance mechanisms and physiological and biochemical mechanisms have been studied.The main results are as follows:1.The induced resistance efficacy,agronomic traits and pod yield of six exogenous chemicals such as salicylic acid,calcium chloride and sodium silicate to peanut web blotch disease and early leaf spot disease were tested.The results indicated that all the used compounds could induce resistance to peanut leaf spot diseases when applied to the plants as a spray treatment.Calcium chloride was most effective for control of web blotch disease?53.01%?and sodium silicate was most effective for control of early leaf spot disease?42.28%?.Besides,the areas under disease progress curve?AUDPC?of Calcium chloride and sodium silicate treatments were significantly lower than others,which were 28.87%?calculated with disease index of web blotch?and 31.77%?based on disease index of early leaf spot?lower than control,respectively.Furthermore,calcium chloride treatment was the best to improve the pod yield of peanut with increased 17.81% compared to water control.2.The effects of Ca Cl2 induced cell membrane permeability and ROS metabolism on the resistance of peanut to web blotch disease were investigated by the greenhouse pot experiment.The result demonstrated that Ca Cl2 treatment might have caused an enhanced level of resistance in peanut against Phoma arachidicola infection.Treatment with 30mmol·L-1 Ca Cl2 was more effective than other concentrations which could cause an increase in disease protection by 53.77%;Ca Cl2 application made the MDA content and REC of leaves lower than with pathogen inoculation alone;Under the pathogen inoculation condition,the Ca Cl2 pre-treated plants could obtain higher generation of ROS in metabolically active leaf tissues;Remarkably increased activities of SOD,CAT and APX in Ca Cl2?30 mmol/l?pre-treated inoculated plants was observed compared to all other treatments and the peak of enzyme activities was reached at 24 h.As mentioned above,a burst of ROS could be triggered by treatment with Ca Cl2 but was eliminated by activation of antioxidant enzymes,which consequently decreased the level of cell membrane damage and induced the defense response against peanut web blotch disease.3.A greenhouse pot experiment was conducted to investigate the changes in chlorophyll content,secondary metabolites such as lignin and phenols in peanut leaves induced by calcium chloride and inoculation with Phoma arachidicola.The activity of POD,PPO,and PAL enzymes in peanut leaves was also tested.The results showed that the total chlorophyll content of peanut leaves treated with different concentrations of Ca Cl2 was significantly higher than that of the group with pathogen inoculation alone.Under the pathogen inoculation condition,Ca Cl2 pre-treated plants could accumulate more lignin and total phenols in the peanut leaves.Ca Cl2 primed plants stimulate significantly high level of secondary metabolism related enzymes such as PAL,PPO and POD in response to pathogen inoculation.The accumulation of these secondary metabolites is closely related to the tissue structure resistance and physiological and biochemical resistance mechanisms of peanut plants,which improves the ability of peanut plants to resist infection by pathogen. |
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