Agronomic performance of transgenic burley tobaccos expressing TVMV or AMV coat protein genes with and without virus challenges

Eighty transgenic tobacco (Nicotiana tabacum L.) lines expressing either the tobacco vein mottling virus (TVMV) coat protein (CP) gene or the alfalfa mosaic virus (AMV) CP gene were evaluated for their agronomic performance with or without virus challenge. All TVMV CP lines were characterized previously for their virus resistance following challenge with three different potyviruses. In the absence of virus challenge, the cured leaf yield of more than 80% of the TVMV CP lines was not significantly different from their non-transgenic counterparts; half of the poor performing lines were in one of the five genetic backgrounds. Similarly, most of the negative variation for yield among the AMV CP transgenic lines was within a single genetic background. Variation for other agronomic traits, including plant height, leaf size, and stalk diameter closely followed the results for yield. Following virus challenge, cured leaf yield of the most resistant transgenic lines was similar to the non-challenged treatment. Among the AMV CP transgenic lines, yield loss following challenge with AMV was reduced from 22 to 30%. These results suggest that the primary selection criterion in a population of transgenic tobacco lines containing a viral CP gene should be for virus resistance, but it must be recognized that variation for agronomic performance may exist among the resistant selections, particularly in some genetic backgrounds.