Sordaria brevicollis is a filamentous ascomycete
previously considered to be exclusively heterothallic.
Here we show that S. brevicollis
can exhibit homothallism, and describe the genetic and environmental factors
favouring the process. Both mating types can produce
perithecia in unmated cultures, but only in the uncrossed perithecia of
mtA are ascospores formed (in <30% of the fruitbodies). In
most cases, only one or two asci are produced in any uncrossed mtA
perithecium, although as many as 13 have been observed. The
ascospores show no segregation for mating type; all are mtA.
Heterokaryon analysis established that meiosis and recombination
occurred during ascospore production in both homothallic and heterothallic
development. Homothallic fruiting is inhibited both by
crossing with the opposite mating type, and by light.