Comparison of germination and primary growth of Ophrys schulzei Bornm. & Fleischm seedling in different culture media under in vitro condition

Ophrys schulzei Bornm. & Fleischm is an orchid species which its underground organ is harvested and has numerous applications in the food and pharmaceutical industries. The population of this orchid species in the natural habitat has been greatly reduced and is at risk of extinction due to the low germination percentage, required specific ecological conditions and also overharvesting. Therefore, it is necessary to evaluate different propagation methods in order to approach ex situ conservation, domestication and cultivation of this plant species. Vegetative propagation of orchids is difficult, time-consuming and expensive, and also a small number of propagules can be obtained from each mother plant. Sexual propagation in ex vitro condition is also difficult due to low endosperm of orchid seeds, undifferentiated embryo and need to symbiosis with mycorrhizal fungi. Therefore, it seems that in vitro seed germination is the most suitable method for producing orchid seedlings. The most important and crucial step in seedlings mass production is selecting appropriate growth media for in vitro cultivation. Therefore, in this research, the effect of different culture media on the germination and seedling growth of Ophrys schulzei was studied.  

In this research, germination, protocorm formation and growth indices of Ophrys schulzei seedlings were evaluated in 5 different culture media including Malmgren, Orchimax, P723,  and . At first, the seeds were sown in the mentioned culture media and transferred to the growth chamber with 25ºC and dark conditions. After germination, they were placed in a refrigerator at 4ºC for two weeks. At the end of two weeks, the culture containers were placed in the growth chamber with 25ºC and light conditions 16/8 h (light/dark). After 12 months from seed sowing, the mentioned factors were evaluated. This research was conducted as a completely randomized design with 5 replications at Research Center of Medicinal Plants Breeding and Development of University of Kurdistan, in 2019-2022.

The highest (25.26%) and lowest (0%) germination percentage were observed in Malmgren and Orchimax culture media, respectively. Protocorms were appeared earlier in the Malmgren medium than other media (19.33 days after seed sowing). Protocorms on  medium were stayed in initial form, and no significant development was observed. Protomeristems were appeared earlier in Malmgren medium compared to P723 and  (105.66 days after seed sowing). There was no significant difference between P723 and  in terms of protomeristem appearance time (1/4 B5 148.33 and P723 159 days after seed sowing). Seedlings were formed only in P723, Malmgren and  culture media. The highest protocorm weight (0.12 g) was belonged to the Malmgren culture medium, and the highest root length (21.44 mm), root weight (0.19 g), aerial weight (0.05 g), seedling length (45.98 mm) and seedling weight (0.37 g) were belonged to the seedlings grown in P723 medium. In terms of the number of roots and shoot length, no significant differences were observed between the three culture media.  

In general, among the studied culture media, Malmgren and P723 were determined the most suitable culture media for production of Ophrys schulzei seedlings.