Genetic variation between strains ofMonilinia fructicolaandMonilinia laxaisolated from cherries in Michigan

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Abstract
Polymerase chain reaction (PCR)-mediated analysis of rDNA from isolates of Monilinia fructicola and Monilinia laxa from Michigan cheny orchards revealed interspecies restriction site variation in the internal transcribed spacer 1 (ITSI) region and length variation in the small subunit (SSU) rRNA gene. 1TS1 sequences from both species were 146 by long; however, the ITSI of M. laxa differed at three positions from the ITSI of M. fructicola. Although the sequences of the ITS1 regions from both species were nearly identical, the enzyme tilrel cuts the PCR-amplified ITSI region of the two species differentially. PCR amplification of the 3′ end of the SSU rRNA gene yielded products of approximately 940 and 520 by from M. fructicola and M. laxa, respectively. A 421-bp group I intron was detected by PCR within the SSU rDNA of 32 isolates of M. fructicola but not in the eight isolates of M. laxa. Intron sequences from each of four isolates of M. fructicola were identical, and the SSU rDNA flanking sequences from these isolates and from two isolates of M. laxa were nearly identical. Arbitrarily primed PCR analysis of genomic DNA with microsatellite primers (GACA)4 and (GTG)5 revealed that the number and size of the amplification products were chazacteristic for each species. Distinctive and reproducible sets of amplification products were obtained from 32 isolates of M. fructicola and the eight isolates of M. laxa. Our results illustrate the potential of PCR amplification of ribosomal and genomic DNA for differentiating these tree-fruit-infecting brown rot fungi.