[Physiological and biochemical bases of xero-tolerance of fungal biocontrol agents and their application].

Hyphomycetes fungal biocontrol agents usually infect host insects by conidial germination and penetration into insect integument under high humidity condition which is generally the restrictive factor for the application of mycoinsecticides in insect control in the field. It is ideal to produce more xero-tolerant inocula (e.g. conidia) of the agents, although the current formulation technology has helped to some degree to reduce the dependence of fungal formulations on the high humidity. This paper reviewed the advance in basic and applied studies on the physiological and biochemical bases of fungal xero-tolerance and its water activity regulation in the past two decades. Possible approaches to make fungal formulations more xero-tolerant were discussed, with an emphasis on the increased accumulation of biologically compatible solutes such as low-molecular polyols and trehalose to the inocula produced for formulation. More efforts are necessitated to understand the mechanisms involved in molecular biology and in regulating the accumulation of the compatible solutes, and to explore for new technology to enhance the xero-tolerance of the fungal agents through biochemical regulation in mass production.