Enhanced Outcrossing, Directional Selection and Transgressive Segregation Drive Evolution of Novel Phenotypes in Hybrid Swarms of the Dutch Elm Disease Pathogen Ophiostoma novo-ulmi
| Autor: | Susan E Kirk, Selma Franceschini, Jack Forster, Clive M. Brasier |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
0106 biological sciences
Microbiology (medical) Ophiostoma QH301-705.5 vegetative compatibility Locus (genetics) Outcrossing Plant Science Biology Subspecies 01 natural sciences Article Transgressive segregation invasive species 03 medical and health sciences hybridisation fitness traits pathogenicity Biology (General) mating type Ecology Evolution Behavior and Systematics 030304 developmental biology Hybrid Genetics 0303 health sciences Directional selection pandemic biology.organism_classification perithecia Dutch elm disease 010606 plant biology & botany |
| Zdroj: | Journal of Fungi Volume 7 Issue 6 Journal of Fungi, Vol 7, Iss 452, p 452 (2021) |
| ISSN: | 2309-608X |
| Popis: | In the 1970s, clones of the two subspecies of Ophiostoma novo-ulmi, subsp. americana (SSAM) and subsp. novo-ulmi (SSNU) began to overlap in Europe, resulting in hybrid swarms. By 1983–1986, hybrids with high, SSAM-like growth and pathogenic fitness comprised ~75% of popula-tions at Limburg, Netherlands and Orvieto, Italy. We resampled these populations in 2008 to examine trends in hybrid fitness traits. Since preliminary sampling in 1979–1980, MAT-1 locus frequency had increased from ~0% to ~32% at Orvieto and 5% to ~43% at Limburg, and vegeta-tive incompatibility type frequency had changed from near clonal to extremely diverse at both sites. This represents an enormous increase in outcrossing and recombination potential, due in part to selective acquisition (under virus pressure) of MAT-1 and vic loci from the resident O. ulmi and in part to SSAM × SSNU hybridisation. Overt virus infection in the 2008 samples was low (~4%), diagnostic SSAM and SSNU cu and col1 loci were recombinant, and no isolates exhib-ited a parental SSAM or SSNU colony pattern. At both sites, mean growth rate and mean patho-genicity to 3–5 m clonal elm were high SSAM-like, indicating sustained directional selection for these characters, though at Orvieto growth rate was slower. The once frequent SSNU-specific up-mut colony dimorphism was largely eliminated at both sites. Perithecia formed by Limburg isolates were mainly an extreme, long-necked SSNU-like form, consistent with transgressive segregation resulting from mismatch of SSAM and SSNU developmental loci. Orvieto isolates produced more parental-like perithecia, suggesting the extreme phenotypes may have been se-lected against. The novel phenotypes in the swarms are remodelling O. novo-ulmi in Europe. Locally adapted genotypes may emerge. |
| Databáze: | OpenAIRE |
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