Abstract
Background
Plant roots may be used as an efficient target tissue for plant transformation assays . In root propagable species transformed roots are able to regenerate into whole plants without the addition of exogenous hormones, thus avoiding somaclonal variation associated with many plant transformation protocols. Plants grown in soil or a soilless solid medium have roots that tend to be extremely delicate and are difficult to sterilize in advance of plant transformation experiments. Axenic tissue culture plants grown on a semi-solid medium are slow to produce large amounts of biomass compared to plants grown in solution-based medium.
Methods
Seeds were germinated and grown for 14 days in 25 mL Petri dishes on half-strength semi-solid Murashige and Skoog medium containing 1% sucrose. Seedlings were then transferred to MagentaTM GA7 vessels containing either liquid or semi-solid ½ MS medium with 0.25, 0.5, 1, 2, or 3% sucrose. In the hydroponics (liquid medium) treatments, expanded clay balls were used to anchor seedlings. Hydroponic vessels were fitted with a sterile air aeration hose and filled ¾ full (100 mL) with liquid ½ MS media. Liquid media were replaced after 7 days. All plants were grown under fluorescent lights for 14 days.
Results
We have developed an improved axenic hydroponic propagation system for producing large quantities of plant roots for use in transformation assays using Taraxacum kok-saghyz as a model for root propagable species. Addition of sucrose up to 2% and use of liquid medium were correlated with an increase in biomass accumulation compared to plants grown on traditional semi-solid media.
Conclusions
Our new axenic hydroponic method yields sufficient quantities of roots for extensive plant transformation/molecular studies. Using this axenic modified Magenta vessel system and described growth conditions, an average 50% increase in root biomass was obtained compared to semi-sold media.