Micropropagation of trifoliate orange (Poncirus trifoliata)

An attempt was made to develop an in vitro regeneration protocol for trifoliate orange (Poncirus trifoliata), the important Phytophthora collar rot tolerant rootstock genotype of citrus. Among different plant growth regulators used, 1 mg/l BAP, 0.5 mg/l NAA, and 40 mg/l adenine sulphate significantly improved culture response including percentage forming shoot buds, days required for shoot initiation, shoot length and number of resultant shoots per explant. Rooting was achieved on half-strength MS medium supplemented with NAA and IBA either in combination or individually at different concentrations. Medium containing 0.5 mg/l IBA + 0.5 mg/l NAA gave the maximum root initiation response. However, the higher number of roots per shoot and highest root length was achieved when half-strength MS medium was fortified with 0.5 mg/l NAA and 0.5 mg/l IBA respectively. The hardening medium consisted of cocopeat and soilrite (2:1) in which the survival rate of hardened plants was found to be 82.2% after one month.