Rapid Clonal Propagation of Papaya in Vitro from Mature Field-grown Trees

Abstract

Rapid development of axillary branches on rooted cuttings from mature field-grown papaya ( Carica papaya L.) trees was promoted by removal of stem apices and application to the cut surface of a mixture containing 225 mg BAP/liter of lanolin. Small axillary buds were removed from these branches and cultured, initially on solid medium, and then in liquid medium on a roller drum at 3 rpm in Drew and Smith (DS) medium containing 1 µ m BAP + 1 µ m NAA. After two or three subcultures on the roller drum with alternate periods on hormone-free basal medium, apically dominant shoots were produced. Growth of axillary buds subsequently occurred on DS medium containing 1 µ m BAP + 0.25 µ m NAA. Cultures also were established from buds of 6-month-old trees, followed by enhanced axillary shoot growth on DS medium containing 2 µ m BAP + 0.5 µ m NAA. Roots initiated on actively growing shoots when incubated at 27°C in a 12-hr photoperiod on a reduced mineral medium containing 10 µ m IBA. Rooted shoots were established in a high-humidity (>90%) cabinet in a glasshouse and planted in the field. Field plants were characterized by a reduced juvenile stage, excessive vegetation at the lower nodes, and production of flowers and fruit close to the ground. Chemical names used: N 6 -benzylaminopurine (BAP); 1 H-naphthaleneacetic acid ( NAA ); 1 H -indole-3-butyric acid (IBA).