An efficient in vitro propagation protocol for direct organogenesis from root explants of a multi-purpose plant, Broussonetia papyrifera (L.) L'H acute accent er. ex Vent.

Broussonetia papyrifera (L.) L'He ' r. ex Vent. is a perennial woody plant used as source material for papermaking, as woody forage, and as traditional Chinese medicine. In this study, an in vitro adventitious shoot induction procedure for B. papyrifera root explants was developed and evaluated the frequency of adventitious shoot regeneration. It showed that the culture medium, treatment with plant growth regulators, explant developmental stage, explant inoculation mode and genotype significantly affected explant regeneration efficiency. The results suggested that the best medium was half-strength Murashige and Skoog (1/2 MS) medium supplemented with 1.0 mg/L 6-benzyladenine (BA), 0.1 mg/L alpha-naphthalene acetic acid (NAA), 0.05 mg/L indole-3-butyric acid (IBA), explants derived from roots at the third development stage, inoculation by horizontal planting without cutting, and the genotype was GZ2, delivering a regeneration frequency of 84.44% and the maximum prolif-eration coefficient was 5.02. The optimal condition for inducing adventitious shoot rooting was 1/2 MS sup-plemented with 0.1 mg/L NAA. Under this condition, the maximum rooting rate of adventitious shoot was 82.22%, and the root grew strongly. Furthermore, the survival rate of transplanted seedlings was > 90%. Although the regeneration system was influenced by the B. papyrifera genotype, it is still effective for all ge-notypes studied. Using this novel system, B. papyrifera root explants can attain high induction rates and pro-liferation coefficients.

Automated summary

By optimizing the culture medium, plant growth regulators, explant developmental stage, inoculation mode, and genotype, the efficiency of adventitious shoot regeneration in Broussonetia papyrifera root explants can be significantly improved. The best regeneration conditions include specific hormone concentrations in the culture medium. Moreover, the transplant survival rate is also high.