High-frequency Shoots Regeneration of an Oil Crop, Simmondsia chinensis (Link) Schneider Using Axillary Buds

Abstract

An improved shoot micropropagation protocol of Simmondsia chinensis (Link) Schneider (jojoba) through axillary-bud proliferation from nodal explants using combination of 6-benzyladenine (BA) and thidiazuron (TDZ) has been developed. Axillary buds were sprouted from nodal segments within two weeks on Murashige and Skoog (MS) medium supplemented with different combinations of BA and TDZ. The presence of TDZ in initiation medium increased the rate of explants with sprouting buds. To avoid adverse effects of prolonged exposure of explants to TDZ, cultures were transferred to TDZ-free MS medium fortified with various concentrations of BA for further multiplication, proliferation and elongation of induced shoots. The highest number of shoots per explant (29.5 ± 1.3) was achieved when 2.5 mgL^-1 BA and 5.0 mgL^-1 TDZ-exposed explants were sub-cultured for 6 weeks on MS medium containing 1.0 mgL^-1 BA. Elongated shoots were rooted on 1/2 MS medium augmented with 2.5 mgL^-1 IBA, which resulted in the highest average number of roots per shoot (7.4 ± 0.9). The regenerated plants were acclimatized and transferred to a growth chamber with 75% survival rate. Our results suggested that combination of BA and TDZ was effective for shoots multiplication and sprouting buds of jojoba explants, and that this protocol would be useful for the large-scale micropropagation of elite jojoba genotypes.