Developing practical protocols for micropropagation of some important pistachio commercial cultivars and 2 selected male varieties.

In this project different stages of micropropagation including surface sterilization, culture establishment, shoot proliferation, rooting, transfering to in vivo conditions and acclimatization of 6 pistachio varieties were optimized in the Department of Tissue Culture and Gene Transformation of Agricultural Biotechnology Research Institute of Iran (ABRII). Suitable strategies to overcome encountered propagation problems including shoot proliferation and rooting were investigated. Plant materials used in this project were both in vitro-germinated seeds and actively-growing healthy current-year twigs from adult trees (15 – 20 years old) of 4 pistachio commercial cultivars (Owhadi, Kalleh Ghoochi, Akbary and Ahmad Aghaii) and 2 male varieties (R-31 and R-20), all supplied by Iranian Pistachio Research Institute (Rafsanjan, Kerman Province). Experiments carried out using twigs in all of the mentioned cultivars showed little or no success in culture establishment due to severe internal contamination and phenolic exudation from the explants. Only a few explants slowly responded. Frequent subculturing every 2-3 days within the first two weeks after initial culture did reduce the phenolic exudation problem but most of the explants did not respond to shoot induction treatments and remained inactive for long time (about 4 months). Severe heading and pruning of the donor trees was carried out in the winter and the young shoots in the spring season were used but this also had little success. However, it was possible to establish cultures from Owhadi and R-31 and shoot proliferation and rooting stages were optimized for them. DKW basal culture medium with doubled concentration of FeNa2EDTA supplemented with B5 vitamins and 2 mg/L BAP was the best medium composition for shoot proliferation of Owhadi and R-31 cultivars. For rooting, a modified MS medium (half strength of its macro and micro elements and normal concentration of FeNa2EDTA) supplemented with 2.5 mg/L NAA and 0.1 mg/L IBA gave the best results. Meanwhile, micropropagation cultures were established quite successfully using in vitro-grown young seedlings of 4 commercial cultivars.