Indian Journal of Experimental Biology Vol. 39, December 200 I, pp. 1280-1287 Morphogenetic responses of six Philodendron cultivars in vitro S Sreekumar, S Mukunthakumar & S Seeni * Plant Bi ot ec hn ology Division, Tropical Botanic Garden and Resea rch ln stitute, Palode, Thiruvananthapuram 695 562, Indi a. Received 12 March 2001; revised 27 August 2001 In vitro morphogen ic response of nodal e xpl a nt s from six cultivars of Philodendron viz, blue mi sti c, pa int ed lady, pink prince, pluto, royal queen a nd g reen emperor was studied. Frequency and number of shoot formation depe nd en the cultivars and co ncentrat ion of BAP. Hi gh frequency and number of shoot fo rmati on were obtained w hen the nodal explants were cultured in Nitsch med ium suppl eme nt ed with BAP (6.8- 11. 8 J1M), suc rose (2%) a nd agar (0.45 %), initi a ll y in the dark for 8- 10 weeks followed by 16 hr ph otope ri od. Regenerated shoots were rooted on medium without growth regulators. Afte r two weeks of hard e nin g, rooted and rootle s shoots were es tabli shed in th e so il with more th an 90 a nd 65 % survival rates re- spe ctively, while the unhardened pl antlets showed a mu ch lower percentage (20%) establishment. A standard protocol for th e rapid multiplication of Philodendron is presented. Philodendrons are of great interest due to their indoor and outdoor decorative value. Among the foli age pl ant s th ey constitute a major share in both domesti c and ex port market and their cost varies from f ew rupees to few thousa nd s per pl ant in loca l nurse rie s. Conventional propaga ti on of Phil ode11.dron by st em cuttings and seeds is slow and inc onsiste nt with th e demand . Micropropagation is th e best opti on to solve thi s problem by providing consistent supply of qu ality plant materials at a des irabl e pace. Although man y private firms are ac tiv e ly inv olved in th e produc ti on and supply of Philode ndrons, th e pro toc ols are known only to th em and as such are not published. Ti ssue culture studies on some spec ie s of Philodendron reported ea rli e rt - 4 essen ti a lly deal with bud proliferation and rooting in vitro bu t a rapid propagation protocol that could be used by others fall short of required demand. It is particularly so since mo rphogenic r es ponse in ti ssue culture is also t.l epcndent on the genotype or the mo th er pl ant a nd var iati ons in res pon se may occ ur , even between cultivars 7 · 8 , that abo und among Philodendrons. In th e prese nt stud y we have in ves ti gated the in vitro re generat ion response of six c ulti va rs of Philodendrons to different cytokinin trea tm e nt s and have also developed mi cropropaga ti on protocols for a ll of the m. Materials and Methods To study the genotypi c effec t, SIX cultivars of * Correspondent author: Ph: 9 1 (0) 472 ll 69226, 869626, 869646: Fax: 9 1 (0) 4 72 369626 Philodendrons (blue mistic, painted lady, pi nk prince, pluto, royal queen and green emperor) were selected. Top shoot cuttings (I 0-15 em long) were collected from 2-3-year-old potted plants of th e selected cultivars maintained in th e germplasm collection at the in stitute. After defoliation , th e cuttin gs were washed we ll in running tap water for 15 min before removing th e leaf sheath(s) covering the axil lary bud. Stem cuttings were th en immersed in 1% (v/v) labolene (Gl axo India Pvt Ltd ., Mumbai) for 15 min and cl ea ned thoroughly. After repeated washing in tap water, noda l seg ment s (0.8- 1.0 em long) we re di ssected in a steril e a ir fl ow hood and th e exp lants were surface sterilized by se ri al passages through 5% (v / v) sodium hypochlorite so luti on for 15 -20 min a nd 0.1 % (w/v) HgCb for 5 min with a rinse in steril e tap wate r in between and 4-5 rinses at th e e nd . Th e brownish dead ti ssue at cut e nd s wa s removed and th e seg me nt s we re immersed in steril e disti li ed wa ter und er constant stirring for 15-20 min to remove exudates. The different basal media test ed includ ed Nitsch 9 and half and full stren gt h sa lt and vitamins of Murashi ge an d Skoog 10 ( MS ), each supplement ed with 2 o/o (w/v) sucrose. After add ing the growth re gulator(s) [6-benzylaminopurine (SA), kin etin ( Kn ), a-naphthaleneacetic ac id (NAA )] , pH of th e med ia was adjusted to 5.5 and 5.8 as th e case may be before adding Difco Bac to agar (0 .45 %). Afrer di sso lvin g th e agar by boilin g, the medium was dispe ns ed in 15 and 50 ml aliquot into cu lture tubes (25 x 15 0 mm ) and conical fl as ks (250 ml) and autoclaved at 12 1 °C and