Restriction Fragment Length Polymorphisms in Nuclear and Mitochondrial DNA ofSclerotiniaSpecies

Abstract

Restriction fragment length polymorphisms were observed in nuclear, ribosomal DNA of S. sclerotiorum, S. minor, S. trifoliorum, S. asari, S. ficariae, Sclerotinia n. sp., and Sclerotiorum ceptivorum. Whole-cell DNAs of 42 isolates were digested separately with EcoRI, BamHI, and HindIII and probed with cloned rDNA fro Neurospora in Southern hybridizations. Cloned rDNAs from Schizophyllum and Armillaria hybridized to the same restriction fragments as did cloned rDNA from Neurospora. Most of the polymorphism in rDNA restriction fragment lengths was between rather than within species, with application as taxonomic characters in comparing species. Specifically, the rDNA restriction fragment phenotypes indicated that the newly discovered species S. asari and Sclerotinia n. sp. are genetically distinct entities, and that the synonymy of S. ficariae under S. sclerotiorum is justified. Three isolates of Sclerotiorum cepivorum had an identical set of rDNA restriction fragment sizes. The rDNA restriction fragment phenotype of this form-species was unique, with no obvious relationship with any of the Sclerotinia species tested. To examine variation in mitochondrial DNA, plasmid pGP637, which carries the mitochondrial 24S rRNA gene from Neurospora crassa, was used as a probe in Southern hybridizations with HindIII-digested DNAs of S. sclerotiorum, S. minor, and S. trifoliorum. There was extensive variations in the restriction fragment sizes of mitochondrial DNA between species, with only one fragment shared by all isolates. Each species had between one and four fragments that were unique to, and constant within, that species. There was considerable variation in the sizes of several other fragments within each of the three species examined.