Degradation Of Plant Virus Transmitted By Bemisia Tabaci Using Plant Polyphenols And Its Mechanism

Bemisia tabaci is one of the most important pests in the world,in addition to causing direct damage on crops by feeding on the plants,it also causes indirect harm o crops by transmitting a variety of plant viruses,which results in serious loss of crop production.For controlling plant viral diseases,prevention is still the main method,and there are few reports on effective treatment of plant viral diseases.Plant polyphenols are important secondary substances of plants,and their sources are extensive and their species are diverse.Screening plant polyphenols with viral scavenging activity should be an important way to explore plant viral therapeutic agents.In this study,the degradation of plant polyphenols such as gossypol and paeonol was studied,and the degradation mechanism was analyzed.It is expected that plant polyphenols such as gossypol can play an active role in the treatment of plant virus diseases.The main results of this paper are as follows:(1)Comparison on the degradation activities of different plant polyphenols against tomato yellow leaf curl virus(TYLCV)by B.tabaci:In order to screen the plant polyphenols with high degradation activities on TYLCV,five different plant polyphenols were compared.The results showed that paeonol and phlormone showed degradation activity on TYLCV,while kaempferol,magnolol and thymol could not degrade TYLCV.After feeding on solution with 500mg/L paeonol or phlormone for five days,the degradation rate of TYLCV carried by B.tabaci was 60%,and the degradation activity on TYLCV by 500mg/L plant polyphenol was significantly higher than that by 100mg/L plant polyphenols.(2)Degradation of TYLCV capsid protein(TYLCV-CP)induced by plant polyphenols in vitro:To analyze the mechanism of virus degradation by plant polyphenols,the effects of paeonol,phloridine and acetate gossypol on the stability of TYLCV-CP in vitro were studied.It was found that all of the three plant polyphenols showed high activity on TYLCV-CP.After treated with 50mg/L paeonol for 6h,250mg/L TYLCV-CP could be effectively degraded.100mg/L phlormamine could effectively degrade 250mg/L TYLCV-CP after treated for 6h.Among the three plant polyphenols,acetate gossypol had the highest degradation activity,and it could effectively degrade 300mg/L TYLCV-CP by treating with 12.5mg/L phenol for 75s.The degradation of TYLCV-CP in vivo was also confirmed by Western blot analysis,the results showed that acetate gossypol could effectively degrade TYLCV-CP in B.tabaci.(3)Evaluation on field efficacy of acetate gossypol on TYLCV:Field trials in Nanjing were conducted to test the antiviral activities of gossypol on tomato plants as well as the incidence and severity of disease using a root-drenching method,after applying 50 or 100 mg/L acetate gossypol.The results indicated that gossypol treatment on tomato plants significantly decreased the incidence of TYLCV in plants.The height of tomato plants before treated with 50,100 mg/L acetate gossypol acetate gossypol and water was 27.8,27.9 and 29 cm respectively.After treatment for 30days,the height of tomato plant with 50 and 100 mg/L acetate gossypol was 70.5cm and 76.4cm,which was significantly higher than that of the control(65.6cm).Eight weeks later,the disease severity of the 50 and 100 mg/L acetate gossypol treatment were 19.61 and 29.63 respectively,and the efficacy were 15.6%and 40.1%respectively.(4)Degradation of various viral capsid proteins by acetate gossypol:Degradation experiments on various virus capsid protein in vitro showed that,the CP of plant virus such as cucumber green mottle virus,sweet potato feather virus and sweet potato chlorotic dwarf virus could be degraded by acetate gossypol,and the CP of animal viruses such as rabbit hemorrhagic disease virus could also be degraded by acetate gossypol.Transmission electron microscopy investigation and HA hemagglutination test showed that,acetate gossypol had a significant negative effect on the morphological size and density of VP60 virus protein of rabbit hemorrhagic disease virus,which thus effectively reduced the titer of VP60 virus protein,and the VP60 protein was entirely destructed by 100mg/L acetate gossypol.