Rapid in vitro propagation of the threatened endemic orchid, Ipsea malabarica (Reichb.f.) J D Hook through protocorm-like bodies.

ABSTRACT

Rapid propagation of I. malabarica (Reichb. f.) J D Hook, an endemic and endangered orchid of the Western Ghats of Kerala, India through conversion of axillary buds to protocorm-like bodies (PLBs), and subsequent plant regeneration was achieved. Growth regulators and sugar displayed significant influence in the induction of PLBs. In vitro derived shoots from field grown rhizomes of Ipsea cultured on Murashige and Skoog (MS) medium with 13.3 microM N6-benzyladenine (BA) containing 2% commercial grade sugar turned the axillary buds to PLBs within 25 days, and developed a mean of 33.1 PLBs within 50 days. Kinetin (KIN) did not induce PLBs, but facilitated axillary bud proliferation. Transfer of PLBs on medium having same concentration of BA and sugar facilitated rapid multiplication, and developed a mean of 47.5 PLBs. No decline of PLB proliferation was observed up to 10th subculture. Half strength MS medium with 6.97 microM KIN facilitated conversion of 98% PLBs to plantlets. On this media, a mean of 5.8 roots were also developed per shoot. Shoots developed bulbs during culture were grown to rhizomes. Increase of sugar to 6 or 8% hastened the development of bulbs/rhizomes. Reintroduction of PLB-derived plantlets in the natural habitat i.e. at Vellarimala (at 1300 m height) of the Western Ghats of Kerala was attempted as a means to assist in situ conservation. This is the first report of conversion of axillary buds to PLBs. The protocol enables to surmount the threat of extinction of this endemic and endangered orchid.