Development of an embryogenic suspension culture of bitter melon (Momordica charantia L.)

We have optimized a system for the somatic embryogenesis via embryogenic suspension cultures in bitter melon (Momordica charantia L.). Friable calli could be induced in 30-day-old leaves on semi-solid MS [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol. Plant. 15, 473–497.] medium supplemented with 1.0 mg/l 2,4-D. Large number of globular embryos (24.6%) were noticed when the calli was subcultured in liquid medium containing 1.5 mg/l 2,4-D. The complete removal of 2,4-D in the later stages of culture, stimulated their further development to heart and torpedo stages. Microscopic examination revealed the ontogeny of somatic cell development via the formation of cell clusters, which then enlarged to pro-embryos, and gave rise to heart and torpedo stages within a period of 2 weeks. Somatic embryos successfully germinated on agarified MS medium with no additional growth regulators. An effect of media, other components and stimulating factors such as carbohydrates, amino acids has also been evaluated for somatic embryogenesis. The full strength MS medium containing 50 mg/l PVP and 40 mg/l glutamine was effective to achieve a high frequency of somatic embryo induction, maturation and further development. An average of 6.2% young plants was achieved from friable callus and was phenotypically normal. To our knowledge, there is no published report on somatic embryogenesis of bitter melon (M. charantia L.) via embryogenic callus or cell suspension cultures. These results are likely to facilitate genetic transformation of bitter melon.