Study of developmental stages and embryogenesis of Thymus daenensis microspors

Thymus daenensis Celak is a valuable medicinal plant containing high thymol content in the essential oil. The domestication and breeding of high quality and homogenous varieties is necessary for its commercial production. The purpose of this study was to regenerate haploid plants from microspore culture. Since, most plant species show the best embryogenesis response at the uninuclear stage of microspore development, in the present study microspore developmental stages were determined. Based on the obtained results, the buds with uninuclear microspores were those of with 1.3-1.4 mm in diameter and 3.8-4.4 mm in length. In order to induce microspore embryogenesis, different pretreatments of temperature (30 and 4°C), hormones (2,4-D: 25, 35 and 45 ppm) and different media (NLN-13, FHG, B5) were investigated. The results indicated that there was a significant difference in response of microspores to different induction media, pre-treatments and their interactions. The highest numbers of multi-cellular structures were observed in the NLN-13 medium and temperature treatment of 30 ºC for 8 days and 2, 4-D treatment of 25 mg/l. Finally, heart shaped embryos were only observed in FHG medium with heat pretreatment for 8 days. Future studies are needed to increase the number of multi-cellular structures and successful regeneration of haploid plants.