Evaluation of resistance to SPFMVs in transgenic sweetpotato by graft-inoculation and aphid transmission

摘要

Viral diseases of the sweetpotato(Ipomoea batatas L.(Lam)) are highly prevalent and often cause serious damage to the plants,particularly the severe strain of the sweetpotato feathery mottle virus(SPFMV-S) that causes‘obizyo-sohi’disease in Japan.The sweetpotato is widely recognised as being prone to infection by sweetpotato feathery mottle virus (SPFMV).Generally,SPFMV is transmitted by aphids(Myzus persicae),and the infected tuberous roots are used for vegetative propagation.To confer viral resistance to SPFMV using current biotechnology,a transgenic sweetpotato has been developed by introducing SPFMV-S coat protein(CP)genes,which have shown a significant resistance to SPFMVS.However,ecological distribution in the field of SPFMVs is unclear,and,neither the transmission of SPFMV using the aphid transmission test nor the aphid transmit theory itself has been established for sweetpotato.Thus,in this study,investigated the ecological distribution of SPFMVs in field-infected sweetpotato,and establishes a testing method for the aphid transmission of SPFMV.Furthermore,the virus resistance nearer to the field was evaluated in transgenic sweetpotato.As a result of some examinations,SPFMV was not capable of independent infection；rather infection by SPFMVs was coincidentally complex in natural conditions.Furthermore,infection was by a dominant strain between complex infecting SPFMVs,and was differentiated by the area of infection.Transgenic sweetpotato plants expressing the SPFMV-S CP gene were challenged by graft-inoculation with field infected SPFMVs.All of the transgenic sweetpotato plants were highly protected in the long term against SPFMVs complex infection compared to the control plants.Next,we establish a testing method for resistance to SPFMV by aphid transmission in sweetpotato.Furthermore,we evaluated the resistance to SPFMV in transgenic sweetpotato using the improved aphid transmission method,and determined higher levels of resistance to SPFMVs in transgenic sweetpotatoes.These results suggest that transgenic sweetpotatoes show resistance to SPFMVs in the field.