Abstract

Carica papaya L. is an economically relevant fruit crop in some tropical and subtropical countries. Though this species shows three polygamous sexual types, commercial production of the fresh fruit is mainly established from hermaphrodite lines. As a result of the cross-pollinating reproductive mechanism of hermaphrodite C. papaya, cultivation areas also show unwanted female plants. Comparatively, hermaphrodite plants exhibit considerable variation in regards to yield, fruit quality, and susceptibility to pathogens. In this context, the present work aimed at establishing a somatic embryogenesis protocol to provide regenerants from leaves of hermaphroditeC. papaya plants. Leaf explants, collected in the rainy season, provided high frequency of friable embryogenic calli (FEC). In culture medium supplemented with 2,4-dichlorophenoxyacetic, FEC overgrew into a yellowish friable mass that fully covered the leaf explants. The somatic embryogenesis process occurred asynchronously, with new globular embryos continuously forming from the FEC. Torpedo and early cotyledonary somatic embryos matured in medium containing polyethylene glycol, activated charcoal and abscisic acid. These embryos were germinated, and normal seedlings were recovered. Based on these outcomes, thetissue culture protocol presented here may be considered a successful alternative for large-scale and clonal propagation of adult hermaphrodite plants of C. papaya.

Key words: Carica papaya, clonal propagation, hermaphrodite plants, leaf explant, somatic embryogenesis.

Abbreviation

Abbreviations: 2,4-D, 2,4-Dichlorophenoxyacetic acid; ABA, abscisic acid; FEC,friable embryogenic calli; MS, Murashige and Skoog; PEG, Polyethylene glycol 2000.