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 most important causal pathogen of cereal bare-patch disease, were paired with each other and with tester strains of other AGs on potato-dextrose agar amended with charcoal (PDCA) to investigate mycelial interactions. Pairings among AG 8 field isolates produced compatible interactions 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 line to barrage reactions. As formation of a tuft indicates that the paired isolates are able to anastomose and to form viable heterokaryons, the testing of mycelial interaction types, highlighted by tuft formation, may be used as a rapid procedure to characterise field isolates of R. solani obtained from cereals