IN VITRO CONSERVATION OF ZIZYPHUS SPINA-CHRISTI L. GERMPLASM BY USING ABSCISIC ACID

Jujube (Zizyphus spina-christi L., also known as napq or sidr) belongs to the buckthorn family (Rhamnaceae). Zizyphus species are important fruit trees for several countries, such as Egypt, India and Gulf area, for the fleshy drupes rich in sugars and vitamins. Traditional tree improvement programs are time-consuming and difficult, and in vitro propagation methods provide an effective alternative. Slow growth storage is a technique that allows in vitro storage of shoots for period ranging from 6 months to 2 years, depending on the species, after which shoots can be returned to standard culture conditions and micropropagated when desired. In this study, slow growth storage of Z. spina-christi was conducted using 0, 7 or 9 mg/L of abscissic acid (ABA) in different media (MS, ½MS and N&N). Conservation was extended for up to 12 months, with observations on the quality of shoots performed every 3 months. Moreover, after each period of slow growth storage, the ABA-treated and untreated shoots were moved back to standard culture conditions and evaluated for their recovery of proliferation. After 12 months of storage, ABA treatment could maintain high survival percentage of shoots that recovered well its proliferation capacity. In particular, the main outcome of the present study is that, on full or half-strength MS medium added of 7 mg/L ABA, it is possible to achieve 12-month storage of nabq shoot cultures, maintaining a good quality level of material and an effective recovery in post-conservation. It has also been observed that the effect of ABA in slow growth storage is mediated by the formulation of the storage medium.