Abstract: Genetic transformation experiments of the different exploids from Citrus grandis cv. Changshou Shatian You infected with Agrobacterium rhizogenes were carried out under dark and light. The optimized culture system for Ri T-DNA transformed roots of C. grandis cv. Changshou Shatian You was constructed as follows: After the ventral wounded striations on the single activation cotyledon were inoculated by A. rhizogenes A4 (logarithmic period), they were cultured at the temperature of 25±2℃ in the dark for 25-30 days, some transformed roots were generated from wounded striations of most cotyledons. The genetic transformation ratio was about (83±11)%. Axenic Ri T-DNA transformed roots (hairy roots ) were harvested after five subcultures. Explants were activated on MT medium. The MS medium was used for subculture of transformed roots. Mass Ri T-DNA transformed roots which the hormone was produced independently were harvested from this optimized culture system. White fresh Ri T-DNA transformed roots were about 1.14±0.07 cm long, 0.73±0.04 mm wide, and grew negative geotropism.

Key words: Citrus grandis cv. Shatian You Changshou, Agrobacterium rhizogenes, Ri T-DNA transformed root, Optimizing culture system