Efficient Genetic Transformation in Lavandin using Agrobacterium rhizogenes as Vector

To develop an efficient procedure for the genetic transformation of lavandin, wild-type Agrobacterium rhizogenes harboring pIG121-Hm was used for infection. β-Glucronidase (GUS) expression was compared in leaf segments and leaf-derived calli as inoculation explants after five days of cocultivation, but GUS expression was only observed on calli. Hairy roots with strong GUS expression formed in 27.3% of these calli. When root segments excised from hairy roots were cultured in media containing various concentrations of 6-benzylamino purine (BA), thidiazuron (TDZ), or N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU), adventitious shoots were formed in some media. The adventitious shoot formation rate depended on the plant-growth regulator, and the highest adventitious shoot formation rate was 77.5%, in medium containing 0.02 mg·L−1 CPPU. This medium was not as effective in the formation of adventitious shoots from calli. Shoots from hairy roots were easily rerooted and acclimatized in a temperature- and light-controlled room. Transformation efficiency was more than six times higher with the Agrobacterium rhizogenes-infected culture series (20.6%) than with the Agrobacterium tumefaciens-infected culture series (3.3%), in terms of the rates of hairy root induction and regeneration from hairy root segments. These results indicate that efficient genetic transformation in lavandin can be achieved with A. rhizogenes as the vector.