GENETIC MAPPING OF THE DIPLOID STRAWBERRY USING RANDOM AMPLIFIED POLYMORPHIC DNA (RAPD) MARKERS

Genetics maps linking molecular/biochemical markers to genes of economic interest have proven to be valuable research and breeding tools in many crops species. Using the Polymerase Chain Reaction (PCR), a new category of molecular markers called RAPD's (Random Amplified Polymorphic DNA's) can be identified in large numbers and used to saturate a molecular linkage map. We are exploiting RAPD's, as well as isozymes and RFLP's (Restriction Fragment Length Polymorphisms), for the purpose of constructing a genetic map, and identifying useful gene tag in the strawberry.

In order to circumvent the genetic complications inherent in the octoploid genomic structure of the commercial strawberry, Fragaria x ananassa, we have begun to construct a strawberry genetic map at the diploid level, using crosses within Fragaria vesca. Having previously identified a close linkage between the isozyme SKDII (shikimate dehydrogenase) and a locus governing red versus yellow fruit color in a cross between diploid cultivars ‘Yellow Wonder’ and ‘Baron Solemacher’, we are not focussing on a wider cross between ‘Yellow Wonder’ and a highly heterozygous wild accession. Segregation of isozymes and RAPD markers in the F₁ generation of this cross has resulted in identification of four linkage groups, the largest of which contains ten markers. Preliminary mapping data from the F₂ generation of this cross, which is segregating for a variety of morphological/physiological traits, will be reported.