Asymbiotic seed germination, direct induction of protocorm-like bodies from protocorms, plantlet regeneration, and greenhouse acclimatization of yellow flowered hybrid Cattleya (Orchidaceae)

Abstract

Protocorm-like bodies (PLBs) multiplication is one of the most preferable in vitro methods to increase the number of orchids that produce very few seeds or seeds that are not able to germinate. In the present study, Protocorm-like bodies (PLBs) were induced directly at high frequency from protocorms of yellow flowered hybrid Cattleya, used as explants. PLBs developed on Murashige and Skoog (MS) medium supplemented with 15% (v/v) coconut water (CW), 0.1% (w/v) activated charcoal (AC) and fortified with 1.0 mg L-1 6-benzylamino-purine (BAP) showed a significantly better growth performance in relation to PLBs formation percentage, number of PLBs per explant, weight of PLBs (g), browning percentage, shoot formation percentage, and number of shoots per explant after 8 weeks of in vitro growth. The highest rooting in the single shoot of yellow flowered hybrid Cattleya (1.0-1.5 cm in length) was achieved on full strength MS medium conjunct with 15% (v/v) CW and 0.3% (w/v) AC which produced 9.50±0.17 mean roots shoot-1 with 19.71±0.15 mm mean root length more efficiently than naphthalene acetic acid (NAA) or indole-3-butyric acid (IBA) after 12 weeks of culture. Regenerated plantlets with well-developed shoot and roots were successfully established in plastic pots containing sterilized coconut husks and grown in the greenhouse with 98% survival rate. There was no difference in the morphology of stock plantlets and regenerated plantlets. Thus, this complete study has successfully outlined a rapid, high frequency direct induction of PLBs of yellow flowered hybrid Cattleya (Orchidaceae) from protocorms inclusive of PLBs proliferation, shoot proliferation, rooting and greenhouse acclimatization.