The suppressiveness potential of plants - An approach for "increasing the richness of the soil"

Abstract

An important function of microbial life in soils consists in the control of soilborne plant pathogens. In the past 30 years this "natural" plant protective potential has moved more and more into the focus of research. This research has frequently demonstrated the high efficacy of the so-called "antiphytopathogenic potential" (coined by REINMUTH, 1963) against a number of important plant pathogens. The "antiphytopathogenic potential", identical to the later termed "soil suppressiveness", works against specific pathogens (fungi, nematodes) on specific locations and soil conditions, whereas the "soil fungistasis" is generally directed against any living microbe in the soil, in any location (LOCKWOOD, 1977). When the antifungal potential in the soil is weakened e.g. by extended monoculturing, a general decline in the productivity is observed with specific sensitive crops. For the existing tough economic circumstances, farmers tend to consider this aspect only, if the consequences are severe and damage or threaten their yields. Only then precautions such as crop rotation or fallows gain practical importance. Biological soil desinfestation may be a modem practical approach of utilizing the "antiphytopathogenic potential" of soils. Antagonistic soil fungi or bacteria such as Trichoderma, Gliocladium, Fusarium, Coniothyrium or Bacillus can be and have been used in the preventive control of soilborne plant pathogens, in particular those which cannot be controlled by synthetic fungicides. In the spirit of VON THUNEN, it may be questioned whether the current intensity and specialisation in agriculture imposes a threat for the soil hygiene. However, since the 1950s yields of chief arable crops in Europe have constantly increased and still continue to increase which strongly contradicts this assumption. Nevertheless, there is some evidence of growing damage induced by specific soilborne pathogens in recent years. These problems will have to be met by developing and applying modem technologies such as biocontrol, breeding for resistance or root protecting fungicides. The strong requirement for such efforts inadvertently results from a continuously growing world population and thus further increasing demands for food in the next decades.