Heterokaryons of Sclerotinia homoeocarpa exhibit enhanced adaptability to multiple fungicide pressures
D. KESSLER (1), J. Hulvey (1), G. Jung (1). (1) University of Massachusetts-Amherst, Amherst, MA, U.S.A.
Heterokaryosis, in which genetically distinct nuclei coexist within a cell, contributes to genotypic and phenotypic plasticity in multinucleate fungi. <i>Sclerotinia homoeocarpa</i>, causal organism of dollar spot of turfgrasses, is a multinucleate fungus with a history of resistance to multiple fungicide classes. We demonstrate that two homokaryons (HOKs), resistant to either a demethylation inhibitor or benzimidazole fungicide, can form heterokaryons (HEKs) with limited dual-fungicide resistance and adaptability to different fungicide pressures. HOKs were co-cultured to give rise to HEKs, which were isolated from the zone of interaction by hyphal tip isolation. HOKs and resultant HEKs were assayed on single and dual-fungicide amended media for resistance. HEKs displayed reduced fungicide sensitivity overall compared to HOKs. Reduced fungicide sensitivity and shifts in genotype indicated that HEKs could adapt to changes in fungicide pressure. Presence of both HOK nuclei in HEKs was confirmed in HEKs by detection of a SNP in the β-tubulin gene, and by the presence of both HOK microsatellite alleles. In fungicide resistance assays, survival of nuclei in HEKs was observed in a dose dependant fashion. Results from this study suggest that <i>S. homoeocarpa</i> HEKs can harbor nuclei with different fungicide resistance profiles. These data also suggest that heterokaryosis is a means by which the pathogen adapts to multiple fungicide pressures through nuclear disproportion.
View Presentation |
