Vegetative and in vitro propagation of the medicinal and ornamental plant Astragalus suberosus subsp. haarbachii (Fabaceae)

A number of Astragalus species (Fabaceae) are utilized for medicinal (secondary metabolites) and ornamental purposes (landscaping), and in food industry for the production of high quality forages and gum. However, the slow seedling development, the poor seed germination capacity and low number of seed set are often drawbacks for their propagation. According to the literature, there is no prior information on the asexual propagation of the Balkan sub-endemic A. suberosus subsp. haarbachii. Propagation experiments were performed to set up a protocol for the vegetative and in vitro propagation of this taxon, suitable at nursery level. In early spring, the base of softwood tip cuttings (7-8 cm) was immersed for 1 min in IBA (0, 1,000, 2,000, 4,000 ppm) solutions and overlapped with 0.066% and 0.2% powdered IBA formula. The cuttings were placed in trays on a peat: perlite (1:3) substrate on a heated greenhouse mist. The most appropriate rooting treatment was the 2,000 ppm IBA (17.3 roots per cutting, 2.7 cm long, 100% rooting) in 5 weeks and the plants' survival rate after 10 weeks was 81.3-100%. Among the three basal culture media (MS, WPM, Gamborg B5) tested in vitro, B5 gave the highest shoot formation percentage (62.5%) and leaf length, MS and B5 gave similar shoot numbers while the percentage of explants' with yellowish leaves was lower in MS. The combined effect of 8 mu M BA + 0.2 mu M IBA (MS medium) gave the highest shoot formation (66.7%), shoot number (1.9) and length (0.9 cm) promoting initial shoot induction. This study contributes to the successful ex situ conservation of A. suberosus subsp. haarbachii, facilitating its further sustainable exploitation.

Automated summary

This study successfully established a protocol for the vegetative and in vitro propagation of the Balkan sub-endemic Astragalus suberosus subsp. haarbachii, contributing to its successful ex situ conservation and further sustainable exploitation.