Genetics of Cronartium ribicola .1. Axenic culture of haploid clones

Genetically pure lines of the mononucleate (haploid) stage of Cronartium ribicola can be grown by isolating mycelium from single spots on infected white pine needles or by culturing single basidiospores on defined media preconditioned by cell-free diffusates of massed germinating basidiospores. Although growth is initially slow, cultures can be increased rapidly by alternately subculturing from solid to liquid media and back again indefinitely. The ability to culture pure haploid clones has important implications for studying the genetic structure and sexual behavior of rust populations and the nature of virulence.