Research PaperPolyethylene glycol and chilling overcome Somatic embryogenesis obstacle in Pyrus communis

- Competence of somatic embryogenesis is genotype-dependent in pear.
- Dar Gazi was known as recalcitrant cultivar and Natanzi as the most competent.
- Endosperm and immature cotyledonary segments are competent for SE pathway.
- Employment of stresses namely, chilling and PEG caused successively progress in SE.

The purpose of this investigation is to achieve the procedure of somatic embryogenesis (SE) as an efficient propagation way in four pear cultivars: Natanzi, Ghosi, Williams and Dar Gazi, by focusing on two strategies: One is the application of competent explants, and the other one is stress employment. The results were variable because of cultivars behavior was highly genotype specific. However, the results identified that the highest frequency of embryogenic callus induction was obtained from the endosperm and immature cotyledonary segment explants of P. communis cultivars on Murashige and Skoog medium (MS) containing 8.05 μM 1-naphthaleneacetic acid (NAA), 13.32 μM N6-benzyladenine (BA) supplemented with 250 mg/L glutamine as a reduced nitrogen source and 30 g/L (w/v) sucrose in Ghosi (75.46%). The optimized media were different for each cultivar in the induction phase, namely, Natanzi and Ghosi in MS, Williams in Schenk and Hildebrandt (SH) and Dar Gazi in Nitsch and Nitsch (NN). Then, it was observed that when embryogenic calli were transferred to the media containing 1% (w/v) Polyethylene glycol (PEG), calli of some cultivars further differed into embryos while other cultivars produced in chilling at 4 °C. Also, maturation of embryos occurred at 4 °C for 4 months. Then passages using MS media caused germination of embryos and plantlets were produced. To sum up, the greatest frequency of embryogenic callus (75.46%) occurred in Ghosi, and the highest embryo maturation and germination (77.06% and 37.66%, respectively in mentioned cultivars) were observed in Natanzi.