Understanding reproductive biology for realization of conservation and sustainable development of Swertia thomsonii C. B. Clarke-an endemic medicinal plant of Western Himalaya

Abstract

Swertia thomsonii an important medicinal plant of Himalaya is more susceptible to extinction in the scenario of anthropogenic threats and global climate change. Therefore a detailed study on reproductive biology was undertaken for its conservation and sustainable use. The present study was conducted with the aim to understand reproductive strategies, breeding behaviour and pollination ecology of this prized, endemic medicinal plant species. It is a perennial rhizomatous herb growing along an altitudinal gradient of 2550–3400 m a.s.l. The flowering commences from the month of August and continuous till September. The variation in floral traits was observed across the altitudinal gradients, which reflects its phenotypic plasticity in these characters that helps the species to get adapted in different environmental conditions. The pollen viability recorded in three study sites viz. Gulmarg (SS-I), Doodhpathri (SS-II), Pahalgam (SS-III) was 89.83 ± 3.1, 75.86 ± 5 and 84.5 ± 2.5% respectively. Stigma becomes receptive 4–5 days after anthesis and reaches its peak on 6–7th day. The presence of typical floral characteristics such as asynchronous anthesis, conspicuous nectaries, spiny exine of pollen, dichogamy, and herkogamy points towards entomophilous and outcrossing nature. Reproductive indices like outcrossing index (OCI), self-incompatibility index (SI) and selfing rate (S) as well as results of bagging experiments also revealed that the species is self as well as cross-compatible. However, fruit and seed set recorded in insect exclusion experiments confirmed its anemophilous nature and therefore species exhibits an ambophilous mode of pollination. Mixed matting is operative in the target plant species, preferring xenogamy followed by geitonogamy and autogamy. The species is pollinated by specialized pollinators which mostly belong to the Order Hymenoptera. Suitable media for in-vitro pollen germination has also been identified; the knowledge about peak stigma receptivity and pollen germination is indispensable for breeding programmes. Thus the scientific information generated in the present study may prove useful in different breeding programmes and conservation of this valuable plant species.