In vitro cloning of female and male Carica papaya through tips of shoots and inflorescences

Raising cultures of proliferating shoots of female and male plants of Carica papaya through shoot apices taken from mature plants was difficult because of high incidence of endogenous bacterial contamination. Whilst they were easily raised through culture of young inflorescences tips of female and male plants. There was no difference in the requirement of nutrients and growth regulators for proliferation of shoots raised from shoot tips or inflorescence tips, but at the initial stage, the different explants differed in their requirement of growth regulators for induction of shoot bud differentiation. BM1, a modification of MS medium was used as the basal medium in all the cases. There was a pronounced callusing tendency in tender shoots initially used for rooting, for which well-developed shoots (< 4 cm long) were found suitable. Rooting was achieved in developed shoots through a 4-step procedure: Step 1-An initial pulse treatment with a high concentration of IBA (10 mg l) using BM3 medium, a modified Knop medium with trace elements and disodium-ferric-ethylene-diaminetetraacetate (Na-Fe-EDTA) of MS medium and 2% sucrose for 24 h; Step 2Their subculture in medium BM2 differing from BM1 in having 50 mg l m-inositol and supplemented with IAA (0.25 mg l) along with AdS (15 mg l) and 2% sucrose for 7 days; Step 3Roots at the cut end of about 95% shoots were visible, after about 10 days, in the same medium as used in Step 1, but having supplements of 3 vitamins, 2 amino acids and 0.25 mg l IAA, while sucrose was removed; and Step 4The just rooted shoots when finally transferred to the semi-sterilized moist Soilrite contained in culture tubes, formed healthy roots without intervening callusing, while the shoots also remained healthy. Such plantlets when ultimately transplanted along with Soilrite plugs to the potted soil showed about 80% transplant success. In vitro-raised plants appeared normal and fruited under field conditions after about 6 months of ex vitro growth.