Sterile seed germination and seedling cultivation of Idesia polycarpa

Idesia polycarpa Maxim. is a high-quality, high-yield, edible oil tree species native to eastern Asia, where it plays important roles in ensuring national food and oil security, promoting ecological development, and facilitating rural revitalization. However, the commercial development of I. polycarpa has been hampered by the fact that it is primarily propagated by seeds, the required dormancy of which leads to low natural germination rates. Tissue culture technology offers the advantages of rapid propagation, high multiplication rates, and independence from seasonal factors, enabling the rapid production of large quantities of high-quality seedlings. The aim of this study was to establish an efficient aseptic germination system for I. polycarpa seeds.

This study utilized I. polycarpa seeds as the experimental material to investigate the effects of different disinfection times, basic medium variations, activated carbon (AC) concentrations, and the types and concentrations of plant growth regulators (PGRs) on aseptic germination. Subsequently, sterile seedlings were used as explants to screen for the effects of sucrose concentration and the types and concentrations of PGRs on rooting. The study also investigated how different substrate ratios and container types influenced the post-transplant survival rate of tissue-cultured I. polycarpa seedlings.

The results showed that the optimal time was 10 min for I. polycarpa seed disinfection with 0.1% HgCl₂. The most suitable medium for I. polycarpa seed germination was 1/2 MS medium supplemented with GA₃ (1.0 mg·L^-1) and AC (1.0 g·L^-1), achieving a germination rate of 96.0%. A sucrose concentration of 10.0 g·L^-1 was most beneficial for rooting. When using a single plant growth regulator, indole-3-butyric acid (IBA) had the most significant effect on I . polycarpa root induction. The optimal medium for root development was Murashige and Skoog (MS) medium supplemented with IBA (0.3 mg·L^-1) and α-naphthyl acetic acid (NAA) (0.5 mg·L^-1), resulting in a 100% rooting rate and an average of 22.17 roots. These roots had an average length of 3.4 cm and were abundant and vigorous. Tissue-cultured seedlings were transplanted into transparent plastic cups containing a mixed substrate of organic nutrient soil (BALTIC PEAT), perlite, and vermiculite in a ratio of 2:1:1 (V/V/V). They grew vigorously, with a survival rate as high as 96.67%. The findings of this study can provide technical support for the factory breeding of I. polycarpa seedlings.