CLONALITY IN SOILBORNE, PLANT-PATHOGENIC FUNGI

Understanding patterns of mating and recombination, gene flow, and drift in fungal populations requires that both sexual and clonal components of reproduction be identified After considering the genetic consequences of clonality, we focus on two species of soilborne, plant-pathogenic fungi with strikingly different modes of clonal propagation for which there is a combination of genetic and spatial data. At one extreme, clones of the root-infecting basidiomycete Armillaria gallica are territorial; each clonal individual arises in a unique mating event and from this point of origin then ramifies vegetatively as rhizomorphs to colonize territories often including the root systems of many adjacent trees in forests, At the other extreme, clones of the plant pathogenic ascomycete Sclerotinia sclerotiorum are dispersive; they are disseminated as sclerotia and ascospores with the result that clones are disconnected from their points of origin, are spatially mixed within agricultural fields, and are capable of movement between widely separated locations.