Four decades of analysis of propagation and conservation studies on the threatened Himalayan medicinal plants

The study reviews various ex-situ conservation methods for threatened Himalayan medicinal plants and reports the availability of 342 publications (in vitro techniques/tissue culture: 197; seed germination: 92; and vegetative propagation: 53) for 58 plant species. Among them, the highest number of publications (276) was for herbaceous life forms, followed by shrubs (34) and trees (32).The review indicated that the most extensive research on propagation was conducted on Picrorhiza kurroa, Dolomiaea costus (Saussurea costus), and Swertia chirayita. According to the literature analysis, GA3 was the most commonly used hormonal treatment across 51 research studies to improve germination percentage, with chilling treatments used in 17 reports. The review also emphasized that the maximum number of publications (43) was found in root induction using IBA, followed by shoot induction using NAA and BAP, and callus induction using 2–4 D and kinetin (26 and 18 publications, respectively). Different plant growth hormones (2–4 D, NAA, IBA (auxin), kinetin, and BAP) are most dominant for in vitro propagation of plants, and Zanthoxylum armatum showed the maximum mean germination time (149.5 days), followed by Rhododendron arboreum (99.3 days). This combination and technique may be used in future research, which can play an essential role in large-scale production and conservation of Himalayan plant species.