Micropropagation and in vitro rooting of Robinia pseudoacacia L. recalcitrant genotypes

In forest production, there is an emerging tendency towards the planting of fast-growing trees as attractive, renewable energy sources. Hence, efforts were made to develop a method of micropropagation by organogenesis of seven clones of black locust (Robinia pseudoacacia L.) that are resistant to propagation by traditional vegetative methods, as well as one plus tree (no. 9755) at the age of 60, to see if the age of the mother plant is a limitation in the micropropagation of black locust trees. Overall results suggest that Murashige and Skoog medium supplemented with 30 g l⁻¹ sucrose, 0.6 mg l⁻¹ 6-benzylaminopurine (BAP) and 0.1 mg l⁻¹ naphthalene acetic acid (NAA) is better for the propagation of each genotype of R. pseudoacacia than Woody Plant Medium with the same growth regulators, and the age of the donor plant does not affect the organogenic potential. Recalcitrance to adventitious rooting from adventitious shoot formation is a major limitation for the clonal micropropagation of forest trees. Our results showed that although the roots were also formed spontaneously in the growth medium without growth hormones for the tested black locust clones, the application of auxin increased the total root length compared to that in the medium with active carbon and control. A significant effect of the additives of hormone and sucrose on the total root length was found. Increasing the sucrose concentration stimulated the induction of roots in each of the tested concentrations (5, 10, 15 or 20 g l⁻¹). Additionally, the change in sugar dose in the rooting medium caused significant differences in total root length.