ABSTRACTFour mating populations, each associated with a distinct asexual stage (anamorph), are presently recognized withinGibberella fujikuroi.We have identified a fifth mating population, termedGibberella fujikuroimating population F, and have correlated it with theFusarium moniliformeanamorph. We have developed female-fertile tester strains that permit reliable detection of other members of this mating population through sexual crosses made under laboratory conditions. Members of this mating population are widely distributed geographically and have been recovered from several states in the United States, the People's Republic of China, Thailand, and the Republic of South Africa.