Immunity to Potato Mop-Top Virus in Nicotiana benthamiana Plants Expressing the Coat Protein Gene Is Effective Against Fungal Inoculation of the Virus. Brian Reavy. Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, U.K. Mohammed Arif, Satoshi Kashiwazaki, Kara D.Webster, and Hugh Barker Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, U.K. MPMI 8:286-291. Accepted 14 November 1994. Copyright This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1995.

Nicotiana benthamiana stem tissue was transformed with Agrobacterium tumefaciens harboring a binary vector containing the potato mop-top virus (PMTV) coat protein (CP) gene. PMTV CP was expressed in large amounts in some of the primary transformants. The five transgenic lines which produced the most CP were selected for resistance testing. Flowers on transformed plants were allowed to self-fertilize. Transgenic seedlings selected from the T seed were mechanically inoculated with two strains of PMTV. Virus multiplication, assayed by infectivity, was detected in only one transgenic plant of 98 inoculated. T1 plants were also highly resistant to graft inoculation; PMTV multiplied in only one plant of 45 inoculated. Transgenic T, seedlings were challenged in a bait test in which they were grown in soil containing viruliferous spores of the vector fungus Spongospora subterranea. In these tests only two plants out of 99 became infected. Of the five transgenic lines tested, plants of three lines were immune to infection following manual, graft, or fungal inoculation.