Propagation and corm development of Brodiaea in liquid cultures

Abstract

In vitro propagation of several species of the Brodiaea complex, corm production and preparation for acclimatization were studied. Clusters of protocorm-like bodies (PLB) formed on small corm sections grown in vitro in agar medium, were transferred to liquid cultures. Ancymidol, included in the liquid proliferation medium in shake flasks or bioreactors, decreased biomass production by about 50%. Aeration in a bioreactor at 0.2 or 1.6 volumes of air per volume of medium min −1 (vvm) yielded similar levels of biomass production. Production of PLB freely circulated in the bioreactor was 159% higher than that for entrapped PLB. It is suggested that circulation was more important for biomass production in the bioreactor than the aeration rate. Aeration reduced ethylene concentration to 26% of the level found in non-aerated cultures. Silver thiosulfate (STS) significantly reduced the level of ethylene to 68% of non-treated cultures. However, the altered levels of ethylene did not affect biomass production. The ratio of inoculum size to media volume affected the growth value. An increase of 263% in corm production was obtained when the PLB of different genotypes were grown on a medium containing 5% sucrose compared with those grown on a medium containing 1% sucrose. Corms differentiated in vitro displayed a similar morphology to corms developed in vivo. Corms on hormone-free medium with decreased ammonium nitrate content and with the addition of mannitol as osmoticum showed increased dormancy. The combination of elevated temperatures, increased light intensity and reduced relative humidity also contributed to the induction of dormancy in corms.