ABSTRACT
As with most other plant diseases, the extent of success in biological control of wheat diseases, especially those caused by soilborne fungi, is determined by the environment. This is especially true in rain-fed crops, especially in Mediterranean-type environments. The low-input agriculture in these regions implies that there is usually little or no attempt made to employ cultural practices to change moisture, pH, or in some instances even the fertility of the soils. These are, however, some of the soil conditions that determine the level of success of biocontrol methods. This becomes a major issue when one extrapolates research results from biocontrol studies of relatively and naturally nutrient-rich soils of the cool temperate, warm tropical, or subtropical regions to the microbially and nutrientimpoverished soils of regions such as southern Australia. Much of the coverage on the biocontrol of wheat diseases in this chapter deals with take-all caused by the fungus Gaeumannomyces graminis var. tritici and Rhizoctonia root rots, with which I am familiar. Most, if not all, major soilborne fungal diseases of wheat are caused by necrotrophs, which tend to be more damaging to crops in nutrientimpoverished soils [1].
