Hybrid sterility and inviability in the parasitic fungal species complex Microbotryum.
Microbotryum violaceum, the anther-smut fungus, forms a complex of sibling species which specialize on different plants. Previous studies have shown the presence of partial ecological isolation and F1 inviability, but did not detect assortative mating apart from a high selfing rate. We investigated other post-mating barriers and show that F1 hybrid sterility, the inability of gametes to mate, increased gradually with the increasing genetic distance between the parents. F2 hybrids showed a reduced ability to infect the plants that was also correlated with the genetic distance. The host on which the F2 hybrids were passaged caused a selection for alleles derived from the pathogen species originally isolated from that host, but this effect was not detectable for the most closely related species. The post-mating barriers thus remain weak among the closest species pairs, suggesting that premating barriers are sufficient to initiate divergence in this system.
De Vienne
D M
DM
Ecologie, Systématique et Evolution, Université Paris-Sud, Orsay Cedex, France.
Refrégier
G
G
Hood
M E
ME
Guigue
A
A
Devier
B
B
Vercken
E
E
Smadja
C
C
Deseille
A
A
Giraud
T
T
D001487:Basidiomycota / Q000235:genetics / Q000502:physiology*; D002678:Chimera / Q000502:physiology*; D020090:Chromosome Segregation / Q000235:genetics; D016681:Genome, Fungal / Q000235:genetics; D005838:Genotype; D005854:Germ Cells / Q000502:physiology; D043563:Receptors, Pheromone / Q000235:genetics
D043563:Receptors, Pheromone