Mutations in the gene encoding Aminodeoxychorismate Synthase confer auxotrophic phenotypes.

To facilitate genetic mapping of developmental mutants of , we produced a genetic marker that combines recessive auxotrophy with dominant positive selection. We first identified the gene affected by the auxotrophic mutation and then replaced it with a cassette that confers antibiotic resistance. This strain may be used to produce bi-parental somatic hybrids with nearly any other strain.