Sexual fertility of forty Fusarium strains from the European Fusarium sambucinum project.

Fungus strains designated as Fusarium sambucinum, F. torulosum, or Fusarium sp. nov. were crossed with MAT1-1 and MAT1-2 tester strains of Gibberella pulicaris. Of the 40 field strains that were crossed with the tester strains, 13 strains produced fertile crosses and 27 strains did not produce fertile crosses. One strain designated as F. torulosum was fertile with a tester strain of G. pulicaris, suggesting that this is an intraspecies cross and that the strain is G. pulicaris, and, consequently, F. sambucinum rather than F. torulosum. The lack of fertile crosses between tester strains and 27 of the 40 field strains suggests that these strains are not G. pulicaris. Although the ability to form a fully fertile cross with a tester strain can determine the species of a fertile strain, it is more problematic to exclude a strain only because it is infertile.