DETECTION OF THE SOURCE OF INFECTION OF APPLE-TREES BY CYLINDROCARPONHETERONEMA USING DNA POLYMORPHISMS

Restriction fragment length polymorphisms (RFLPs) of the ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) of isolates of Cylindrocarpon he teronema were analysed using rDNA from Saccharomyces carlsbergensis an d mtDNA from C. heteronema as probes. These analyses revealed intraspe cific heterogeneity; four rDNA and six mtDNA restriction pattern categ ories were observed among the isolates tested. The two main rDNA RFLP categories, both of which subdivided into two mtDNA categories, detect ed within the UK isolates could not be associated with the localities from which they were obtained, but the majority of isolates originatin g from trees produced in the same nursery, irrespective of where they were finally planted, belonged to the same category.