Book with abstracts from the COST Action 0905 meeting in ... - UMB

ROOT ENHANCEMENT FOR CROP IMPROVEMENT
Thomas Schmülling
Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität
Berlin, D-14195 Germany
The root system is an important plant organ, and optimized root system architecture is
relevant to overcome yield limitations in crop plants caused by shortages in water or
nutrients. Development of the root system is under control of both environmental and
genetic factors. Classic breeding approaches for optimizing root systems are difficult
because the trait is governed by many genes and is difficult to score. We have chosen a
metabolic engineering approach to generate transgenic Arabidopsis, tobacco and oilseed
rape plants with enhanced root-specific degradation of the hormone cytokinin, a negative
regulator of root growth. Compared to wild type plants, these transgenic plants form a
larger root system, whereas growth and development of the shoot are similar to the wild
type. Elongation of the primary root, root branching and root biomass formation was
increased by up to 80% in transgenic lines, causing an enhanced root-to-shoot ratio. Thus,
it was demonstrated that a single dominant gene could be used to regulate to a great extent
a complex trait, root growth. Plants with a larger root system had a higher survival rate
after severe drought treatment. The accumulation of several elements, including micro- and
macronutrients, was significantly increased in the aerial plant parts. This indicates that our
approach could be used for the biofortification of crop plants or for phytoremediation of
metal-contaminated soils.