Investigation of germination loss in several orthodox tree seeds preserved in natural resources gene bank of Iran

The research was performed on reduction of seed germination capability of seven forest tree species which had been stored in natural resources gene bank, Iran. Rhus coriaria, Smirnovia turkestana and Seidlitzia rosmarinus (2 accessions) were stored for 10 years whereas, Pinus pinea, P. pinaster, P. radiata (2 accessions) and Prosopis stephaniana were stored for 22 years at 5 ºC. Two separate experiments were carried out based on the storage periods. A completely randomized design with three replications was used for each experiment. Results showed that there were significant differences between the accessions for reduction of germination. Regarding the accessions stored for 10 years, Seidlitzia rosmarinus (from 69 to 63%), Rhus coriaria  and Smirnovia turkestana (from 95 to 18.3%) had the lowest and highest reduction in germination, respectively. Seed origin effect was significant on Seidlitzia rosmarinus in such a way that the seeds collected from Khuzestan had more reduction in germination than seeds collected from Yazd. Based on the second experiment, Pinus pinea with Turkey origin and P. radiata collected from North Khorasan province, Iran, had the highest (from 71 to 11.6%) and the lowest (from 82.6 to 52.6%) germination reduction, respectively. Although the studied seeds are orthodox, but there are considerable differences among them regarding to seed deterioration. It is suggested that conservation program of the plant genetic resources via seed needs a flexible management with regard to the effects of species and their origin.