FEMALE FERTILITY AND MATING-TYPE DISTRIBUTION IN A SOUTH-AFRICAN POPULATION OF FUSARIUM-SUBGLUTINANS F SP. PINI

Fusarium subglutinans f. sp. pini is the causal agent of pitch canker disease of pines. The initial occurrence of F. subglutinans f. sp. pin i in South Africa was limited to a single nursery, and isolates from t his population are capable of reproducing sexually, We determined the effective population number, N-e, of this population by using mating t ype and male/hermaphrodite polymorphisms as indicators. The effective population number for mating type, N-e(mt), is 99% of the count (total population), and that for male/hermaphrodite status, N-e(f), is 42 to 46% of the count (total population), The number of strains that can f unction as the female parent limits the effective population number of this population, If this population is stable, then, depending upon a ssumptions about mutation and selection, sexual reproduction need occu r only once per 26 to 153 asexual generations to maintain this level o f sexual fertility.