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Invasion of wood by basidiomycetous fungi. IV. Microbiological approach to the role of kratovirulence in the expression of pathovirulence
Author(s) -
Gramss G.
Publication year - 1987
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/jobm.3620270503
Subject(s) - biology , competition (biology) , population , inoculation , host (biology) , antagonism , microbiology and biotechnology , botany , ecology , horticulture , genetics , demography , receptor , sociology
Abstract Thirty one members of a phytophatologicaly relevant choice of wood‐destorying basidiomycetous fungi WBF) that range from early pathogens to late saprophytes were exposed to each other in dual culture tests in nearly all possible combinations. Patogens in general dispose of the patho‐virulence (PV) capacity to grow in standing host wood in spite of the tre's live defence responses. Their lackin kratovirulence (KV, competitive saprophytic ability), however, excludes them from colonizing downed host wood as they fail to repress and kill its heavily antagonistic microflora. In contrast, saprophytes can control the antagonistic mixed population in dead wood. Their lack poor microbial antagonism. In recent understory‐tree inoculations one group of pathogens colonized stem wood through drill holes which were pre‐infected with antagonistic competitors while another group died back under the pressure of tree defense responses and/or microbial angagonism. The dual culture tests between model organisms such as WBF do not help decide whether this dieback is actually caused by microbial antagonoms. A final decision can only be drived. With a certain probability, from dual cultures between WBF and the original competitor microroganims of standing timber, for it is shown that the competive ability of a WBF against individuals of groups of deputy microbia is extremely seleective (SCA, selective competitive ability). This ability of one organism to overgrow others was expressed in a competition figure. Top competition figures against other WBF are found among pathogens that normally fail to control mixed microbial populations. Minimum competition figures are surprisingly found in the late saprophytes which excellently compete with mixed microbial populations. Among the 14 WBF with low competition figure only 21% cause severe symptom expression in artifically inoculated standing timber, while among the 17 WBF with high competition figure, 59% induce considerable stem deecay. This comparison strongly suggests that the expression of pathovirulence in living wood is at least in part supported by a minimum level of kratovirulence.