In keeping with their inbred history, the two F2 families differ noticeably from the three, random-bred G0 families, in having almost 100 fewer markers mapped (526 vs. 623) and many fewer ab × cd mating types (1.0 vs. 18.7, on average; Table 1).
Our own examination of the heterothallic O. ulmi W9 genome shows that it has an N-terminal-truncated nonfunctional copy of MAT1-1-1 in its MAT1-2 idiomorph, as do many other mating-type-2 Sordariomycetes (fig. 7).
One additional relevant aspect of the tetrapolar system is that MAT loci are often highly polymorphic bringing forth species with many allelic forms that can produce up to thousands of mating types [ 16, 20- 23].
Its sexual cycle also has been the subject of many studies, starting in the 1950s with Leupold's work on mating types and followed by Egel's pioneering work (Egel 1973 , 1989 Egel and Egel-Mitani 1974; Leupold 1993).
It is not known if these gamones should be considered as sex pheromones, reminiscent of those known in many animals (for example, certain insects), but they seem to serve the similar purpose of attracting or bringing together different mating types.
Many, especially single-celled, eukaryotes can reproduce clonally, but still they sometimes undergo sexual reproduction; a traditional example is that of mating types in yeasts.
Using mating crosses, mating types were assigned to ten isolates of the heterothallic fungal species Ophiostoma quercus.
Diploid strains were constructed by mating haploid strains of opposite mating types in YPD medium.
However, it is rare to hear of multiple mating types.
