Micropropagation of Jujube (Ziziphus jujuba)

Jujube (Ziziphus jujuba) is one of the most important fruit trees in Asia which has been planted from 3,000 years ago in China for medicinal purposes. Jujube belongs to the Rhamnaceae family. The Jujube fruit is used in fresh and dry forms. The fruit is full of vitamin C and has anticancer and medicinal effects. This tree can grow on salty and dry lands in Iran. Therefore, increasing the cultivation area of Jujube can be effective for soil conservation. In the last 20years, cultivation of Jujube is is considerable in Iran specially in the South Khorasan Province and 98 % of total production of Jujube in Iran belongs to this province. The low rate of seed germination and low production of shootlets are the most important problems in Jujube proliferation, so micropropagation of this plant through tissue culture was considered. In this study, Cangan ecotype of Jujube was used for multiple shoot regeneration. At the end of May, apical buds of shoots were cut from mature trees of the Research Collection of Jujube at Sarbishe, Birjand, South Khorasan Province in Iran. The buds were disinfected with 70% ethanol for 1 min and 2% sodium hypoclorite for 25 min. Then the buds were rinsed with distilled water for 25 min completely. Apical buds were placed on Murashige and Skoog (MS) medium supplemented with different concentrations of BA (0.5, 1, 1.5, 2 mg/L) in combination with IBA or NAA (0, 0.1, 0.2, 0.4 mg/L). After one month, the shoots with 3-5 cm length were transferred to rooting media (1/2 MS + IBA or IAA: 0.5, 2, 5, 10 mg/L). The data were recorded after shooting and rooting and were analysed in the facorial experiment. The results of variance analysis and mean comparisons showed that there are differences between different levels of IBA and BA alone for the number of shoots and their length (P<0.01). Their interaction effect was also significant. Based on the results, the highest number of shoot inductions (4.25 shoots per explant) was obtained on a medium containing 0.2mg/L IBA + 1 mg/L BA. The longest shoots (5.12 cm) were also observed in MS medium supplemented by 0.2 mg/L IBA and 1 mg/L BA. Increasing the ratio of BA to IBA more than 5 times, caused decrease in shoot production. Totally, the ratio of auxin to cytokinin and also their concentration can determine the success of shooting; because when the BA increased to 2 mg/L and the IBA was 0.4 mg/L the ratio was 5 times, but the shooting decreased. NAA (0.4 mg/L) + BA (1 mg/L) was the best hormonal combinations for high shoot regeneration (3.75 shoots per explant) and its lenght (5.87 cm). In most studies on Ziziphus genus, the combination of NAA and BA is preferred for shooting at in vitro culture. Regenerated shoots were rooted on ½MS medium supplemented with different levels of IAA and IBA (0.5, 2, 5 and 10 mg/L). The highest number of root inductions (7 roots per shoot) were observed on ½MS with 2 mg/L of IAA and it was not significantly different from 2 mg/L of IBA. The longest roots (5.25 cm) were observed in ½ MS medium suplemented by 2 mg/L of IBA and it was not different from 2 mg/L of IAA. So, there is no difference between IBA and IAA for rooting because both of them induced suitable roots for adaptation. IBA is synthetic auxin and is not sensitive to light; so its useispreferred for commercial micropropagation. The rooted shoots were rinsed by water to remove the residual of medium, and then they were transferred to pots containing vermiculite and soil (1:1). Acclimation of shoots was good with 92% survived shoots in the greenhouse. The results of this study showed that the equal ratio of auxin and cytokinin caused a decrease in shooting and high callugenesis. The produced shoots have suitable length and appearance. According to the results, a combination of BA (1 to 1.5 mg/L) with low concentration of IBA(0.2 mg/L) or NAA (0.4 mg/L) has the best shooting, and a weak auxin such as IBA or IAA with low concentration is good for rooting. So, this method can be used for micropropagation of Jujube in commercial scale in our country.