Effects of sugars and abscisic acid on somatic embryogenesis from melon (Cucumis melo L.) expanded cotyledon

Effects of sugars and abscisic acid (ABA) on somatic embryogenesis from mel on (Cucumis melo L.) expanded cotyledon and changes in ABA content on cultu res on the various sucrose treatment media were investigated. Sucrose induc ed somatic embryogenesis, but mannitol did not. Two hundred millimolar sucr ose treatments were optimal for somatic embryogenesis; the formation of som atic embryos was suppressed at lower or higher sucrose concentrations. The frequency of somatic embryogenesis, however, was increased by the addition of mannitol to the initial medium, even if the sucrose concentration was le ss than 200 mM. Somatic embryogenesis was enhanced by the addition of 0.5 m uM ABA to 200 mM sucrose treatment. In the 200 mM sucrose treatment, in whi ch somatic embryos were easily formed, endogenous levels of ABA in callus i ncreased greatly after 2 weeks of culture. ABA content of embryogenic callu s was markedly higher than that of nonembryonic callus at any given period. These results indicate that ABA formation, which was controlled by osmotic conditions induced by the sugars, could be involved in somatic embryogenes is. (C) 2001 Elsevier Science B.V. All rights reserved.