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Liquid Culture Systems for in vitro Plant Propagation

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Chapter 30<br />

Mass propagation of conifer trees <strong>in</strong> liquid cultures -<br />

progress towards commercialization<br />

Pramod K. Gupta & Roger Timmis<br />

Weyerhaeuser Co., Federal Way, WA 98063 USA<br />

Abstract: At Weyerhaeuser Company, somatic embryo production <strong>in</strong> liquid medium and<br />

manufactured seed delivery has been developed to reduce labor costs and <strong>in</strong>crease efficiency<br />

of mass clonal propagation. We have scaled-up embryonal suspensor masses (ESM) of<br />

Douglas-fir <strong>in</strong> 1-litre liquid medium flasks. Over 10,000 somatic embryos have been<br />

produced from a s<strong>in</strong>gle flask. We have cryostored ESM of over 700 genotypes <strong>in</strong> liquid<br />

nitrogen. Somatic embryos of Douglas-fir have also been produced from liquid medium <strong>in</strong> a<br />

bioreactor. Different types of bioreactors are required <strong>for</strong> embryo multiplication and <strong>for</strong><br />

cotyledonary embryo development. Over 250,000 Douglas-fir somatic seedl<strong>in</strong>gs from a large<br />

number of genotypes have been produced <strong>for</strong> clonal field tests.<br />

Key words: bioreactor, Douglas-fir, manufactured seed, somatic embryos<br />

Abbreviation: ABA – abscisic acid, ESM – embryonal suspensor mass, GA – gibberellic<br />

acid, PEG – polyethylene glycol<br />

1. Introduction<br />

Mass propagation via tissue culture is more expensive <strong>in</strong> many plant<br />

species than conventional vegetative propagation such as by cutt<strong>in</strong>gs and this<br />

often limits its commercial application. Labor costs generally account <strong>for</strong><br />

60% or more of the total production costs of <strong>in</strong> <strong>vitro</strong> propagation. These can<br />

be lowered by robotic automation of a few steps of the micropropagation<br />

process by robots or by use of somatic embryogenesis.<br />

Somatic embryogenesis is the process <strong>for</strong> development of embryos from<br />

somatic cells. It is accomplished by tak<strong>in</strong>g cultures through a series of<br />

developmental stages that are similar to zygotic embryogenesis. Somatic<br />

embryo development <strong>in</strong> liquid medium with automation offers tremendous<br />

389<br />

A.K. Hvoslef-Eide and W. Preil (eds.), <strong>Liquid</strong> <strong>Culture</strong> <strong>Systems</strong> <strong>for</strong> <strong>in</strong> <strong>vitro</strong> <strong>Plant</strong> <strong>Propagation</strong>, 389–402.<br />

© 2005 Spr<strong>in</strong>ger. Pr<strong>in</strong>ted <strong>in</strong> the Netherlands.

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