Efficacy of Endogenous Satellite Expression to Confer Resistance to CMV in Satellite Transgenic Tomato under Field Conditions

Abstract

Viral satellite RNA associated with cucumber mosaic virus (CMV) is know to modulate CMV symptomology. Virulent CMV associated RNA 5 (CARNA 5) satellites may intensify crop disease. Naturally occurring variants of these satellites, however, attenuate CMV symptoms. Satellite transgenic tomato plants expressing the S-CARNA 5 or 1-CARNA 5 ameliorating forms of the satellite were evaluated under simulated CMV epidemic conditions in USDA–APHIS approved field trials. Trials conducted at Beltsville, Md., in 1994 and 1995 demonstrated that CMV can be effectively controlled under field conditions in satellite transgenic plants. Yields of transgenic lines infected with CMV were 50%–65% greater than that of non-transgenic infected controls. Yields of noninfected transgenic lines ranged from 5% greater than, to 33% less than, noninfected nontransgenic controls. Expression of CARNA 5 in inoculated transgenic plants greatly reduced CMV foliar symptoms and virus titers when compared to inoculated control plants. Levels of CARNA 5 were detected at varying levels in infected transgenic plants throughout the growing season. Virus or satellite was not detected in samples collected from tomato border plants and weeds growing inside and outside a nonhost crop border surrounding the test plot. Field tests conducted in 1996 will evaluate transgenic tomato plants with a double construct coding for the CMV coat protein gene and 1-CARNA 5 satellite.