An efficient protocol for in vitro propagation of an important ornamental terrestrial orchid, Doritis pulcherima Lindl. through axillary shoot and direct protocorm-like body (PLB) formation from shoot tip explants derived from sixmonth-old axenic seedlings has been described. Shoot tips were cultured on modified nutrient medium of Knudson's C supplemented with 0.1% peptone and combination of various concentrations of NAA and BAP. The effect of NAA and BAP on axillary shoot formation, protocorm-like body induction and root regeneration from the explants was significant. The highest frequency of axillary shoot formation was recorded in the medium containing 2 mg/l BAP and the PLB production was higher in the medium containing 2 mg/l NAA. A higher concentration of BAP showed inhibitory effects on the axillary shoot formation and PLB induction. Efficient root regeneration was observed in low concentration of NAA. However, the profuse root formation was common in the PGR free medium. Rooted plantlets were hardened successfully through the stepwise acclimation protocol and platelets were finally established in the potting mixture containing small pieces of dead tree bark of mango, charcoal pieces and broken bricks in 1 : 2 : 1 ratio.

An efficient method of plant regeneration and subsequent growth and development of Dendrobium hybrid Sonia was developed using intact seedling, shoot tip and thin cell layer. Maximum number of PLBs was obtained in MS liquid medium supplemented with 0.5 mg/l NAA and 1mg/l BAP through shoot tip and thin cell layer culture (TCL). Highest number of adventitious shoot formation was recorded in 0.5 mg/l of NAA and 2 mg/l of BAP through shoot tip culture. In shoot tip and TCL cultures, the necrosis was checked in presence of NAA (0.5 mg/l) and BAP (1 mg/l). Maximum callus frequency was recorded in NAA and BAP (0.5 mg/l) through thin cell layer culture. Direct PLB formation was better at 1.0 μM concentration in all the three polyamines tested. Three polyamines tested were effective in direct PLB formation as well as adventitious shoots. Plant Tissue Cult. & Biotech. 30(1): 77-86, 2020 (June)

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For initiation of seed germination and protocorm growth in Vanda tessellata (Roxb.) Hook. ex G. Don different media, namely Knudson’s C basal medium, modified Knudson’s C basal medium, Murashige and Skoog basal medium, Vacin and Went basal medium and Lindeman basal medium either alone or supplemented with vitamin or 0.1% peptone (w/v) were used. Vitamin mixture was consisted of nicotinic acid, pyridoxine and thiamine HCl at 1 : 1 : 10, respectively. For the initiation of germination, all the treatments exhibited promising results without showing significant variation. But the rate of survival of the germinated seedlings was remarkably low in all the basal media. Maximum survival rate of germinated seedlings was recorded in MS + 0.1% peptone. Necrosis of protocorms was a common phenomenon in all the treatments and 100% necrosis was recorded in LM basal medium and LM + vitamin. Addition of vitamin mixture and peptone in the basal media increased the rate of survival as well as differentiation of the germinated protocorms. Maximum rooted plantlets were recorded in VW + 0.1% peptone Plant Tissue Cult. & Biotech. 30(2): 285-295, 2020 (December)