Genetically stable cell lines of cucumber for the large‐scale production of diploid somatic embryos

Abstract

J. 1996. Genetically stable celi lines of cucumber for the large-scale production of diploid somatic embryos. -Physiol. Plant. 97: 303-310.For the initiation of embr\'ogenic cucumber (Cucumis sativus L.) cell lines, from excised radicles, directly in liquid medium, the culture regime, explant density' and type and concentration of hormones were adjusted so that pro-embryogenic masses (PEMs) were formed within about 8 weeks. The established cucumber cell lines were maintained for severai years without loss of embryogenic and genetic stability. The ploidy level of somatic embryos from different cucumber eel! lines was either diploid or tetraploid and depended on the ploidy level of Ihe cell line. Cucumber cell lines that produced only diploid embryos were obtained by selecting completely diploid explant material and growing 11 in the dark during the initiation phase, Mixoploid explants could lead to tetraploid or mixoploid cell lines. Isolation and additional selection and subculturing of single PEMs resulted in either completely diploid or tetraploid eel! lines, indicating that all ceils of individual PEMs are either diploid or tetraploid. The embryogenic cucumber cell lines, differing only in ploidy level, were indistinguishable in growth rate and embrj'ogenic potential and were genetically stable over several years. Kev words -Cucumis sativus, genetic stability, somatic embryogenesis.M. Kreuger (corresponding author,.^48) et aL.

Long-term suspension cultures of cucumber (Cucumis sativus L.) with high embryogenic potential

“…The embryogenic potential during the long-term culture gradually decreased, starting at 388 ± 57 till 30 ± 11 embryos per ml of PCV at the end. This is comparable with the results of Kreuger et al (1996), who maintained cell suspensions for longer than 36 months and exceeds Sarreb et al (2002), who maintained the cell suspension for 26 months.…”

“…1), which is also typical for embryogenic cell suspensions of carrot (de Vries et al 1988;Toonen et al 1994), cucumber (Wróblewski et al 1995;Kreuger et al 1996), and other species. The cells were of meristematic character, cytoplasm-rich with small The densities of the inoculum affected the growth of the cell population in the suspension (Fig.…”

“…The use of liquid medium throughout the whole process allows long-term maintenance, including genetic and embryogenic stability, making possible a large-scale production of somatic embryos (Kreuger et al 1996). The transfer of cucumber PEMs from a liquid auxin-containing medium to a liquid auxin-free medium led also to the formation of somatic embryos.…”

“…The cucumber embryogenic cell line was initiated and maintained in cytokinin-free media containing 2,4-D as the sole growth regulator (cytokinin-independent culture), in contrast to most described cucumber embryogenic cell suspensions (Kreuger et al 1996;Pellinen et al 1997). Wróblewski et al (1995) initiated and maintained cucumber embryogenic cell suspension also in cytokinin-free media, but the suspension was derived from 1.5 mm vegetative shoot apices.…”

“…Embryogenic cell suspension cultures have been initiated from primary explants by an indirect pathway via the callus stages (Malepszy and Solarek 1986;Callebaut et al 1987;Chee and Tricoli 1988;Bergervoet et al 1989;Raharjo and Punja 1994;Schulze et al 1995;Vengadesan et al 2005), or by a direct pathway in liquid medium from the vegetative shoot apices (Wróblewski et al 1995) and from radicles of germinated cucumber seeds (Kreuger et al 1996;Pellinen et al 1997). The main limitation of cucumber embryogenesis has, until now, been the high frequency of abnormal embryos formation combined with a low frequency of plant regeneration (Cade et al 1990;Debeaujon and Branchard 1993;Wróblewski et al 1995;Pellinen et al 1997;Łady_ zyński et al 2002).…”