The Production of Pyrethrins by In Vitro Systems

Abstract

Pyrethrins comprise a group of six structurally closed related esters. Economically, they are the most important natural plant insecticides. The principal source of pyrethrins is the plant Chrysanthemum cinerariaefolium (Pyrethrum). The industrial production is based on the extraction of pyrethrins from the dried flower heads of the field-grown plant. Harvesting of the flowers is labor intensive and the natural pyrethrins are not plentiful enough to provide for the global market demands. Thus, attempts have been aimed at alternative in vitro production of pyrethrins, by means of plant cell suspension cultures, callus cultures, shoot/root cultures, and the bioconversions of precursors.

Callus and cell suspension cultures of Pyrethrum seems not to be feasible for an industrial process, although technology for cell suspension cultures exist. The dedifferentiation of plant tissue in vitro, necessary to produce a callus and suspension culture, is accompanied by an apparent loss of ability to produce and accumulate pyrethrins. Plantlets and morphologically differentiated shoot cultures (not roots), which produce significant amounts of pyrethrins, could be potential candidates for an industrial process. However, pyrethrins production levels in these cultures is still very low when compared with floral tissue, and large-scale organ culture technology is not yet feasible. Bioconversion of available precursors, by isolated plant enzymes or by genetically engineered microorganisms, appears to be a more attractive approach today. The first small steps have been made, but technological and economical feasibility of this technology is still uncertain.

Key Words:

• Pyrethrum
• Chrysanthemum cinerariaefolium
• plant cell/tissue cultures
• in vitro tissues
• bioconversions
• economics
• commercialization