Bridging Plant Biotechnology and Field Research
Mary Ann L. Smith
A comparison of woody transplants rooted in vitro (left) or removed from culture and rooted ex vitro in soil (right). A video image analysis system records the superior root structure produced ex vitro.
New biotechnological strategies to manipulate plant germplasm in vitro have advanced at a staggering rate. Despite the intensive research interest in plant biotechnology, scientific progress and commercial exploitation frequently have been blocked at the crucial "transition" stage - from novel plant regenerates exhibiting superior growth or stress tolerance in the laboratory to field-proven crop plants.
The common obstacles to this transition are twofold: 1) characteristics evident in cell culture may not be expressed at the whole-plant level under natural production conditions, and 2) rooting and acclimatization of in vitro plants to field or greenhouse conditions may result in serious losses in plant survival rates and quality. Research efficiently linking laboratory biotechnology and traditional field-performance research is needed to foster rapid, practical realization of the gains offered through biotechnology. To enhance this transition, we have developed whole plant microculture (WPMC) intermediate testing systems and video-image analysis systems.
A WPMC system can provide a small-scale, efficient, highly controlled test environment for regenerates from cell culture, to verify that traits selected at the cell level are still expressed in the whole plant. For example, definitive and reproducible detection of superior salt tolerance traits for turfgrasses, tomatoes, and greenhouse floriculture crops have been achieved in rigorously controlled WPMC systems. With the aid of a computer, a video camera processes images of test microplants and allows subtle detection of plant responses to salt stress in the root and shoot zones. The image analysis system automates collection of data about plant growth, development, and disease symptoms. Traits evaluated in WPMC have correlated well with traits measured in vivo in field or growth chamber tests.
The transition from biotechnology research to production can also be obstructed at the stages of rooting and acclimatization, so that regenerates from culture can be evaluated in vivo. In some cases, the regenerated plants that survive transition have abnormal growth and poor tolerance to environmental stress.
Quantitative and qualitative differences in root character after in vitro and ex vitro rhizogenesis, or rooting initiation, dictates plant survival and has long-term repercussions for mature woody specimens that we originally produced in vitro. The nondestructive advantage of using images to evaluate plant quality has allowed us to identify specific factors that affect regenerated clones' chances for survival. This information provides new clues on how to manipulate in vitro strategies to ensure ultimate production of superior plant selections for either field or landscape conditions.
Research systems combining WPMC and image analysis, as described here, provide an excellent means to efficiently evaluate and use novel genetic material in terms of whole-plant attributes.
Mary Ann L. Smith, associate professor of plant physiology
