Superoxide Generation in Chemically Activated Resistance of Barley in Response to Inoculation with the Powdery Mildew Fungus. Superoxid Bildung während Chemisch Aktivierter Resistenz in Gerste als Reaktion auf Inokulation mit Echtem Gerstenmehltau

Mycoparasitic activities of various isolates of Trich! oderma viride\ T[ harzianum\ T[ hamatum\ T[ lon`! ibrachiatum\ T[ konin`ii\ T[ pseudokonin`ii\ Gliocladium virens and Laetisaria arvalis were studied against a serious plant pathogen\ Botryodiplodia theobromae by scanning electron microscopy "SEM#[ Macroscopic observations of fungal growth in dual!cultures revealed that most of the isolates made hyphal contact with the pathogen within 1 days after inoculation\ leading to the inhibition in pathogen growth[ However\ T[ viride Tv!3\ T[ hamatum and T[ pseudokonin`ii inhibited pathogen growth before hyphal contact and exhibited an inhibition zone between the colonies of both fungi[ SEM investigations dem! onstrated that in case of hyphal interaction\ the _rm binding of antagonists "T[ viride Tv!0 + Tv!2\ T[ har! zianum Th!0 + Th!1\ T[ lon`ibrachiatum and L[ arvalis# to B[ theobromae hyphae established either by coiling around its hyphae\ or by penetrating its hyphal cells by forming hooks\ haustoria and appressoria!like structures which invariably led to cell disruption[ Although T[ kon! in`ii and G[ virens Gv!1+Gv!2 did not interact physically by way of coiling and penetration\ they produced wall lytic enzymes or antifungal substances after coming in contact with B[ theobromae which caused wrinklingbursting and collapsing of pathogen mycelium[ It istherefore\ suggested that the outcome of the interaction of antagonist and pathogen was most likely determined by initial hyphal contact that triggered a series of events in pathogen degradation[