MYCELIAL INTERACTIONS AND THE POTENTIAL USE OF TUFT FORMATION IN CHARACTERIZING RHIZOCTONIA-SOLANI ISOLATES INFECTING CEREALS

Field isolates of Rhizoctonia solani anastomosis group (AG) 8, the mos t important causal pathogen of cereal bare-patch disease, were paired with each other and with tester strains of other AGs on potato-dextros e agar amended with charcoal (PDCA) to investigate mycelial interactio ns. Pairings among AG 8 field isolates produced compatible interaction s of either tuft or merging reactions. Tufts formed between all paired field isolates from different pectic zymogram groups (ZGs) within AG 8, but pairings between genetically identical isolates showed merging reactions. Pairings of AG 8 field isolates with the tester strains of the other AGs led to incompatible interactions varying from merging li ne to barrage reactions. As formation of a tuft indicates that the pai red isolates are able to anastomose and to form viable heterokaryons, the testing of mycelial interaction types, highlighted by tuft formati on, may be used as a rapid procedure to characterise field isolates of R. solani obtained from cereals.