The long-term ambient storage-induced alterations in seed viability, germination and seedling vigour of Saussurea costus, a critically endangered medicinal herb of North West Himalaya

Abstract

Saussurea costus (Falc.) Lipschitz (Asteraceae), an economically important medicinal herb, is categorized as critically endangered. The plant is cultivated in some parts of Lahaul (Himachal Pradesh, India) in North West Himalaya. However, in the recent past, the cultivation has declined owing to an array of reasons including a long cultivation cycle, greater profits from other cash crops (mainly pea, potato, hops) and formalities to be completed in obtaining the export permits. Therefore, the possibilities of ex situ (in areas other than Lahaul) cultivation/conservation needs to be explored. In this context, the understanding of seed physiological characteristics would be of immense help. Since there is a dearth of information concerning the storage-depenedent changes in seed physiological status of S. costus, we have analyzed these aspects for a long-term ambient storage (66 months) in a population from Lahaul. The freshly harvested seeds exhibited high viability (95%) with 65% germination that could be enhanced through GA3 and chilling pre-treatments. During storage, the seed germination increased after 12 months suggesting the seeds to be partially dormant that required an after-ripening prior to the commencement of germination. GA3 and chilling treatments appeared to substitute such requirement. Further, the seed viability was completely maintained at least for 18 months and even after 30 months storage, 82% viability retention associated with the production of healthy seedlings was evident. However, beyond 30-month-storage, both seed viability and germination declined substantially. Maintenance of reasonably high viability status, germination and seedling vigour even after substantial storage of seeds under ambient conditions suggests the suitability of seeds for regeneration/cultivation of this species.