Agrobacterium rhizogenes-mediated genetic transformation system
plays an important role in the identification of functional genes. To establish Agrobacterium rhizogenes-mediated genetic transformation system in Eucalyptus， the different strains infected the leaves and stems of Eucalyptus urophylla × E. grandis were used to select the appropriate A. rhizogenes strains and explant types， and the effects of Agrobacterium concentration and infection time on hairy root induction were explored. The results showed that MSU440 was the optimal A. rhizogenes strain and leaves was the preferred explants for hairy root induction. The highest hairy root induction rate reached 81.0% with the average root length of hairy roots was 3.23 cm. The leaves were infected by MSU440 which grown to a bacterial density of 0.3（OD600） for 30 min， then they were co-cultured for 48h and transferred the selection medium supplemented with 20 mg·L-1 Kanamycin. The exogenous genes were stably integrated in the genome of Eucalyptus hair roots which confirmed by PCR analyses and GUS staining， and the transformation efficiency reached 20.2%. In our study， an A. rhizogenes-mediated genetic transformation system of Eucalyptus was preliminarily established， which laid a foundation for gene function identification and further transgenic breeding of Eucalyptus.
