In vitro conservation and production of vigorous and desiccate tolerant synthetic seeds in Stevia rebaudiana

Abstract

Artificial (Synthetic) seed production along with microprpagation can solve many problems with regeneration of Stevia rebaudiana, which produce tiny and non-viable seeds. Shoot tips and axillary buds nodal segments were used from in vitro cultures for encapsulation. The explants were taken from green houses and tissue culture laboratory of AgriBiotech Research Farms, Lahore, Pakistan. Different concentrations of sodium alginate and calcium chloride affect the shape and germination of artificial seeds. A gelling matrix of 3% sodium alginate and 100 mM calcium chloride was found most suitable for the formation of firm, clear and isodiametric ideal beads. No effect of the duration of sodium alginate treatment on bead formation was observed. However, timing of CaCl2 treatment proved to be crucial with 100 mM CaCl2, treatment time of 15 min was suitable for isodiametric bead formation. The synthetic seeds pre-treated with KN03 germinated earlier than seeds without pretreatment with KNO3. Root formation took place after 15 days of shoot formation without addition of any auxin. In liquid medium, the frequency of conversion was high. Frequency to plantlet conversion of synthetic seeds decreased gradually as the storage duration at 4°C increased. After 15, 30, 45 and 60 days of storage, frequencies to plantlet conversion from encapsulated and non-encapsulated segments were 86, 63, 50, 23.3 60.3, 40, 20.6 and 10%, respectively. Key words: Stevia rebaudiana, synthetic seed, in vitro conservation, Na-Alginate, encapsulation.