Doi:10.3906/tar-1406-144 Identification and functional annotation of expressed sequence tags based SSR markers of Stevia rebaudian

Swertia chirayita (family Gentianaceae), is a high-demand temperate pluri-annual critically endangered medicinal plant demanding immediate in situ and ex situ conservation efforts, for which understanding of its breeding behaviour, ploidy status, etc, is important. Pollination studies conducted reveal this species to be both self as well as cross compatible, as 91.60% fruit set in open pollination conditions, 87.60% under controlled xenogamy, 44.20% under geitonogamy and 34.80% under autogamy are obtained. The flower is protogynous and the stigma becomes receptive to pollen germination while still in bud condition, which would allow forced bud pollination for hybrid development. The species is genomic allotetraploid (2n = 26) with about 69% pollen stainable. Flowering and fruiting commence during August to November in its third year of growth, after which the whole plant dies.

The critically endangered Nardostachys grandiflora DC is a highly renowned medicinal and aromatic plant of the Western Himalayan region, traditionally used in treating heart palpitations, convulsions, epilepsy and insomnia, as well as being a source of aromatic oil used as incense, flavoring agent and in quality perfumes. This species is on the verge of extinction due to over-exploitation and habitat destruction and needs immediate preventive measures. Despite being essential for domestication, there have been few studies of the natural variation, breeding and genetic system of this species possibly due to its remote location and sparse populations. The present study has revealed that N. grandiflora, which is restricted to specific ecological niches in high alpine regions 3000–5000 m asl, is under stress due to its infrequent flowering nature, which limits generation of new variation, although some intra-population variability with regard to lamina margin (dentate and wavy) and type of stigma (capitate and trilobed) were observed. This limited variability prevents the species from colonizing new niches, as it mostly multiplies through rhizome ramets. Several interesting features have also been revealed, e.g. presence of bicolpate, tricolpate, tetracolpate and pentacolpate pollen grains as well as isobilateral, decussate and tetrahedral types of tetrad within the same or in different flowers. This study also establishes a new diploid chromosome number (2n = 78), the plant’s genomic allohexaploidy, up to 58% cross pollination; protoandry, its infrequent flowering nature, a high pollen ovule ratio of 6135 ± 327.86 per flower and poor seed set.