MYCELIAL COMPATIBILITY OF Fusarium graminearum SPECIES COMPLEX ISOLATES FROM CROP RESIDUES IN A FIELD WITH WHEAT/SOYBEAN ROTATION

BONACCI, M.; CHIOTTA, M.L.; BARROS, G.

Congreso; XI Congreso Argentino de Microbiología General SAMIGE; 2015

Members of Fusarium graminearum species complex (FGSC) are economically important pathogens of cereals crops causing yield and quality losses in their production. In Argentina, soybean often is used in rotation with wheat in a reduced till or no-till system. Species within the FGSC can survive in crop residues left on the surface, increasing the inoculum density and providing an inoculum source for wheat infections in subsequent year. In filamentous fungi, the ability to distinguish self from non-self is essential for vegetative growth, sexual reproduction and defense against pathogen invasion. This vegetative non-self-recognition could be identified by micelial incompatibility assay. The aim of the present work was to differentiate genotypes in FGSC isolates that could be interacting in crop residues. Fifty isolates of FGSC isolated from crop residues in a field with wheat/soybean rotation were selected for this study. For test mycelial compatibility interactions, 1225 pairs representing all possible combinations of FGSC isolates were grown on V8-soybean medium and incubated at 25°C for 5-7 days. A compatible reaction was indicated by mycelial continuity between the interacting colonies without a zone line. An incompatible reaction was indicated by formation of a barrage zone (thick mycelial layer and/or a dark pigmented line between the paired isolates). All FGSC isolates were self-compatible, except for two isolates that were excluded from further analysis. Out of 1175 pairings between isolates, 104 were compatibles representing 8,9% of the pairings. These results showed a high level of diversity within the population of FGSC as it was suggested in previous studies using vegetative incompatibility (VCG analysis) and amplified fragment length polymorphism (AFLP) markers. Mutually compatible isolates had very different patterns of compatibility with the other isolates. This suggests that barrage formation is determined by different, although possibility overlapping set of loci to those controlling vegetative compatibility.