Cyanogenic potential of cultured cells, tissues, plants and seedlings of cassava
1995
Nambisan, Bala | Mukherjee, A.
The cyanogenic potential of cassava tissues is determined by linamarin levels and endogenous linamarase activity. Tissue linamarin content depends on the rate of biosynthesis, the transport to and from the tissue, and the rate of degradation and conversion to asparagine. Little information is available on the extent to which these processes influence the linamarin content in edible roots. The cyanogenic potential of in vitro cassava cultures and of cassava seedlings, at various developmental stages, was studied to develop a model system for studying cyanogenesis in cassava. Callus cultures were developed from anther, leaf, and stem tissues, and rooting was induced from anther and leaf callus. Linamarin was not detected in callus tissue nor in roots developed from callus; however, linamarase was present in both callus tissue and roots. Cells prepared from anther callus in suspension cultures elaborated linamarase, but did not synthesize linamarin. Shoot (including leaves) and root tissues of meristem-derived plantlets contained both linamarin and linamarase. Root linamarin ranged from 5 to 30 mg/kg dry weight. The presence of linamarin in roots of plantlets and its absence in callus roots suggested that leaf tissue is the primary biosynthetic site. Studies on germinating seeds also revealed that cotyledon tissue had a very high biosynthetic potential (more than 1000 mo CN/kg). These different systems, with varying cyanogenic potential, may serve as effective tools for studying cyanogenesis in cassava.
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