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Mating-Type Gene Structure and Spatial Distribution of Didymella tanaceti in Pyrethrum Fields
Tamieka L Pearce1, Jason B Scott1, Frank S Hay1
1First and second authors: Tasmanian Institute of Agriculture, School of Land and Food, University of Tasmania, Burnie, Tasmania 7320, Australia; and third and fourth authors: Cornell University, School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, NY 14456.
Phytopathology
|July 12, 2016
Summary
Didymella tanaceti, the cause of pyrethrum tan spot, is heterothallic with a 1:1 mating-type ratio. Despite failed crosses, cryptic sexual reproduction is suggested by field population genetics.
Area of Science:
- Mycology
- Plant Pathology
- Population Genetics
Background:
- Tan spot, caused by Didymella tanaceti, affects pyrethrum (Tanacetum cinerariifolium).
- Understanding the role of sexual reproduction in fungal pathogens is crucial for disease management and evolutionary studies.
- The mating-type (MAT) gene system governs sexual reproduction in fungi.
Purpose of the Study:
- To investigate the mating system of Didymella tanaceti.
- To determine the evolutionary role of ascospores in this fungus.
- To analyze the genetic structure and mating-type distribution in field populations.
Main Methods:
- Examined the structure and arrangement of mating-type (MAT) genes in Didymella tanaceti isolates.
- Developed and applied a multiplex MAT-specific polymerase chain reaction (PCR) assay.
- Genotyped 325 isolates from four fields in Tasmania, Australia, analyzing their spatial distribution.
Main Results:
- All isolates possessed either a MAT1-1 or MAT1-2 idiomorph, confirming heterothallism.
- A 1:1 ratio of mating-types was observed in field populations, with random spatial distribution.
- Evidence of reduced selection pressure on MAT1-1 isolates was found, with a second haplotype identified in 4.4% of these isolates.
Conclusions:
- Didymella tanaceti is heterothallic, with both mating-types present in equal frequencies in field populations.
- Although sexual reproduction could not be induced in vitro, the population genetics suggest a cryptic sexual mode of reproduction.
- Further research is needed to fully elucidate the sexual cycle and its contribution to the population dynamics of this pathogen.
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