Induction of roots on jujube softwood cuttings using Agrobacterium rhizogenes

Cuttings from trees of jujube (Ziziphus jujuba Mill.), particularly mature ones, root with great difficulty. A greenhouse experiment assessed the effects of two strains of Agrobacterium rhizogenes (A4 and TR105) on softwood cuttings from two sources: ten year old trees of cv. Li and a tree approximately 40 years old of the cv. Contorta. The cuttings were collected and trimmed to 7.5 cm. Ten weeks after inoculation, both strain and source of cutting influenced visible symptoms of infection. Jujube cuttings were more responsive to TR105 than to A4, and the 'Li' cuttings were more responsive than 'Contorta' cuttings. Strain TR105 was very effective in increasing rooting percentages and root number. 'Li' cuttings had better rooting percentages, greater root number, and greater root length than did the 'Contorta' cuttings. Inoculation with A. rhizogenes may also possess great potential for promoting adventitious root formation in other difficult woody ornamental or fruit tree species.