Reproductive biology of cassava (Manihot esculenta Crantz) and isolation of experimental field trials

Cassava (Manihot esculenta Crantz) is a vitally important food source for many people in devel- oping tropical countries. There are signifi cant opportunities for improving the compositional qualities and pest resistance of cassava, and modern biotechnology is expected to play an important role in these improvements. The test- ing and development of genetically modifi ed cassava will of course be subject to regulatory review, and experimental fi eld trials must be performed in a fashion that prevents gene fl ow from the regulated plants. Methods to ensure reproductive isolation will be derived from a fundamental understanding of the biology of the crop. A current and comprehensive docu- ment on cassava reproductive biology is not yet available but is essential to guide regulators and scientists in planning and evaluating measures for reproductive isolation of confi ned fi eld trials. This paper compiles a current view of the repro- ductive biology of cassava for use in experimen- tal design and regulation of confi ned fi eld trials. With the current state of knowledge on gene fl ow and seed dormancy in cassava, three methods for reproductive isolation of regulated experi- mental plots may currently be recommended: (i) removal of fl ower buds before fl owering, (ii) destruction of plants before fl owering, and (iii) fl oral bagging to contain pollen and seed. Areas for further research in cassava biology and bio- safety are suggested.