SPECIFICITY OF ATTACHMENT OF FUNGAL PARASITES TO THEIR HOSTS

1. Attachment of fungal parasites to their hosts is one of the first events required for parasitism. Attachment usually takes place together with recognition, which decides the outcome of the interaction between two interacting species. 2. Although the mechanism for the specificity of attachment of fungal parasites to their hosts has not been fully clarified, studies of the past 20 years in morphology, biochemistry, and physiology have contributed to our knowledge on this subject. In some host - fungal parasite systems, the specificity is established by parasite recognition of specific surface topography and cell wall ultrastructure of the hosts. In most host - fungal parasite systems, the specificity is determined through binding of complementary macromolecules on the surfaces of both the host and the parasite. These macromolecules were found to be proteins or glycoproteins (some are agglutinins) and carbohydrates. Pretreatments of the host and parasite with some physical, chemical, or biochemical agents can significantly or totally inhibit attachment. 3. The formation of appressoria by fungal parasites on the surfaces of their hosts can be considered as a response of successful attachment and recognition. Attachment to different parts of a host by its parasite can induce differential development of infection structures of the pathogen, and direct attachment is essential for the initiation of host resistance responses. All of these interaction characteristics can be attributed to the specificity of attachment. 4. Until now, information on the genetics of the specificity of attachment has been poor. However, genetic and molecular mechanisms underlying specificity are suggested to be based on the gene for gene hypothesis. Obviously, further work along these lines, aided by monoclonal antibodies and recombinant DNA technology, is needed for complete explanations of the specificity of attachment of fungal parasites to their hosts.