Genetic variation among and within Monilinia species causing brown rot of stone and pome fruits

Nucleotide sequence analysis of the internal transcribed spacer (ITS) regions 1 and 2 of the ribosomal DNA (rDNA) divided the three brown rot pathogens Monilinia laxa, M. fructicola and M. fructigena into four distinct groups. Isolates of M. fructigena received from Japan, which varied by 5 base substitutions in the ITS region from the European M. fructigena isolates, formed the fourth group. Four of five Japanese isolates of M. fructicola tested varied from the New World isolates in that they did not possess a group-I intron in the small subunit (SSU) rDNA. RAPD-PCR data indicated that isolates of M. laxa varied but were randomly distributed worldwide; ITS data indicated no apparent distinction between those from Malus spp. and those from Prunus spp. M. fructigena similarly did not cluster according to geographic origin. In contrast, M. fructicola isolates tended to be clustered according to their origin; Japanese isolates of M. fructicola clustered together and showed similarity to some of the New Zealand isolates. Isolates from USA and Australia were more variable.