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Pak. J. Bot., 44(5): 1669-1676, 2012.

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IN VITRO MASS PROPAGATION OF HERMAPHRODITIC CARICA PAPAYA CV. MEIZHONGHONG

KUNLIN WU, SONGJUN ZENG^*, ZHILIN CHEN AND JUN DUAN

Abstract: An efficient In vitro regeneration system was developed for rapid clonal propagation of hermaphroditic Carica papaya cv. Meizhonghong using shoot buds from seedlings and axillary buds from greenhouse and field fruit-bearing plants. Explants from seedlings were more easily disinfected and initiated, and had higher multiplication rates and rooting percentages than explants from mature plants. The highest percentage of contamination-free explants from seedlings was 81.7% using AgNO₃ treatment after conventional disinfection, which was higher than the antibiotic treatments. Shoot initiation was achieved in Murashige & Skoog (MS) medium with 0.5 mg l^–1 6-benzyladenine (BA) and 40 g l^–1 sucrose. An average of 6.7 fold proliferation rate per subculture was obtained on MS medium containing 0.25 mg l^–1 BA and 40 g l^–1 sucrose after five subcultures. Shoot elongation was induced in MS medium supplemented with 0.25 mg l^–1 BA and 1.0 mg l^–1 GA₃ and 40 g l^–1 sucrose. Cultures were maintained for 20 months (22 subcultures) without any loss in multiplication rate or change in growth habit. The 3/2 MS medium (i.e. with 1.5 times the macro-elements of MS) with 500 mg l^–1 activated charcoal and 5 g l^–1 sucrose was optimum for root development. In the greenhouse, bags with sand (1/3 v) over a mixture of sieved peat and vermiculite (1:1 v/v) were used and 87% of plants survived. About 100,000 plantlets were produced successfully for field growth within three years. Compared to mother plants, the In vitro raised plants were all hermaphrodites and showed no distinct phenotypic variation. This regeneration system is suitable for mass multiplication of cv. Meizhonghong.

Key Laboratory of South China Agricultural Plant Genetics and Breeding, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, People’s Republic of China

^*Corresponding author’s e-mail: zengsongjun@scib.ac.cn; Phone: +86-20-37252993