Conserved primers were used in a polymerase chain reaction to
amplify the ITS region of the rDNA of 100 Microdochium nivale
isolates collected from different turfgrasses in southern Ontario. The
profile of the restriction digestion of the amplified ITS region
revealed that all the M. nivale isolates analysed belonged to
var.
nivale. RAPD profiling and RFLP analyses of the IGS regions of
rDNA revealed extensive genetic diversity within var. nivale.
With RAPD markers, the average similarity coefficient was 66% and
the estimate of genotypic diversity was 0·179. Population subdivision
analysis showed that 92·2% of the total genetic diversity was
found among individuals within populations compared to 7·8% among
populations. In dendrograms derived from genetic distances
using RAPD and IGS-RFLP markers, there was some evidence for host
specialization. Most RAPD markers were shared by
individuals from different turfgrasses, and the populations were not
highly differentiated. The high level of genotypic diversity
detected within populations and the low level of genetic differentiation
among populations show that recombination and migration
are likely playing important roles in the population biology of M.
nivale var. nivale.