Field evaluation of an interspecific hybrid as a containment strategy for plant-made pharmaceutical applications in tobacco.
Biotechnology allows plants to be utilized for the production of non-native pharmaceutical and industrial materials with tobacco being the most commonly exploited plant for these applications. Genetic containment is a concern for these plant expression technologies because of strict USDA regulations requiring no outcrossing with commercial tobacco and no unauthorized release of transgenic seed. An interspecific cross between N. tabacum and N. glauca was tested to assess the level of sterility for contained field production.
Parental lines were engineered for expression of green fluorescent protein (GFP) and homozygous lines were crossed to produce the hybrid. A modified Nelder-wheel with curved, radial arms was utilized for the field test design. Fifty hybrid plants and fifty fertile N. tabacum plants were grown in the center of the plot to evaluate the sterility of the hybrids. Groups of five male-sterile plants (cv. MSTN 90) were placed at specified distances from the center plot to measure the outcrossing potential of the hybrid.
Mature seed pods were collected from both the hybrids and the MSTN 90 plants. A small percentage of the hybrid flowers produced mature seed pods and most of them did not contain any seeds. The few seeds that were produced either did not germinate, or if they did germinate, the seedlings lacked vigor and often perished. Pods collected on the MSTN 90 plants produced more viable seed but less than .0006% of the germinated seedlings expressed GFP.
The results suggest that although the hybrids are not fully sterile, the probability of seed set from selfing, or cross pollination from fertile pollen sources, as well as the incidence of outcrossing to compatible species is extremely low.