In vitro minimal growth and pollen cryostorage as an approach to restoration of threatened forest tree species, Oroxylum indicum (L.) Benth. ex Kurz

Planting tree species is a sustainable approach to achieve landscape restoration but maintaining the diverse native flora of the region being restored is also very crucial to guarantee balanced representation by all species. Many tree species are facing threat to existence in their natural habitats owing to land degradation, competition and anthropological activities. Oroxylum indicum (Bignoniaceae), is one of those species which is categorized as threatened due to overexploitation combined with poor seed set, rare pollinators and low seed viability. Hence the plant needs to be conserved through appropriate strategies and in vitro conservation of germplasm in the form of plant cultures and pollen grains offers a suitable alternative. The research presented here describes the effect of culture medium modifications on medium term storage of cultures in O. indicum as well as methods for cryostorage of pollens from the species. For minimal growth, modifications in the form of decreased macronutrients (1/2 and 1/4), increased sucrose (5%) and use of mannitol (1%) in the medium were done. The shoot length and leaf number decreased during minimal growth treatments with respect to control and could be proliferated again in regrowth medium comprising of Murashige and Skoog’s growth medium along with kinetin and glutamine in 0.5 mg L-1and 25 mg L-1 concentration, respectively. For pollen conservation, initial moisture of the collected pollens was determined as 28% and viability was almost 100% when germinated on in vitro medium containing boric acid, chlorides of calcium and potassium, magnesium sulfate, and sucrose. The pollens could be stored for 3-6 months in -196oC temperature and remain 55% and 20% viable after three and six months, respectively. The findings will help devise methods to proper management of germplasm resources in this species through ex situ conservation so that the conserved plants can be reintroduced into degraded natural habitat of the species. Since the species has wide uses and has been utilized by traditional Indian communities, conserving its population would ultimately also benefit livelihoods of people associated with it.