Rice plant (Oryza sativa L.) containing Rice tungro spherical virus (RTSV) coat protein transgenes are resistant to virus infection

The coat protein (CP) genes CP1, CP2 and CP3 of Rice tungro spherical virus (RTSV) were introduced individually or together to indica and/or japonica rice cells by particle bombardment and transgenic plants were produced. Plants derived from selfed progeny of the primary transformants were subjected to virus inoculation via leafhoppers, the natural vector of the virus. Sixteen out of the nineteen selected transgenic plant lines, as well as their R1, R2 and/or R3 progeny that contained the target gene, accumulated transcripts of the chimeric CP gene(s) by RNA blot analysis. We obtained evidence of moderate levels of protection to RTSV infection, ranging from 17% to 73% of seedlings that escaped infection and a significant delay of virus replication under greenhouse conditions in plant lines that expressed the RTSV-CP1, CP2 and CP3 genes singly or together. There was not an additive effect on resistance when more than one CP gene is expressed. This study is the first to report pathogen-derived resistance to infection by RTSV, one of the two viruses that are involved in rice tungro disease. It is also the first example of CP-mediated protection against a virus that contains more than one CP gene from the same virus.