THE ABILITY OF PLANT-PATHOGENIC MICROORGANISMS TO SURVIVE IN SOIL A SUMMARIZING REFLECTION

The importance of soil as inoculum source for plant pathogenic bacteri a and fungi is stated. Plant parasites have developed several modes of survival in absence of host plants. For many of them the survival in soil is essential. By examples, the differences between real soil-inha biting plant parasites and species having only randomly invaded soil a re described. Parasites continuously occurring in soil and organisms w ith a typical soil stage in their life cycle cause the so-called soil- borne diseases. For these plant pathogens, soil is the most essential inoculum source. In 2nd part of the paper as the most important kinds of survival of parasites in soil and plant residues are mentioned: the infection of alternative host plants the commensalism in the microhab itat rhizosphere the entrance in the saprophytic way of life the produ ction of resting cells (bacteria) or special resting organs (fungi). I n this connection, the physiological abilities providing for the long survival of the resting structure of the causal agents in soil are dis cussed. Finally, the possibilities to influence the survival of plant pathogens in soil by agricultural measurements as an important compoun d of integrated plant protection are considered.