Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Proceedings
Publication Acceptance Date: January 26, 2000
Publication Date: N/A
Interpretive Summary: Because of the importance of the strawberry industry and the large number of strawberry cultivars grown today, there is a pressing need to develop reliable methods for distinguishing cultivars and for assessing genetic diversity in strawberry germplasm for breeding purposes. Traditionally, cultivar identification of strawberry has been based on visual inspection of leaves, flowers, and fruits. The amount of genetic diversity has typically been estimated through analysis of pedigrees. Both of these approaches are limited in their usefulness, however. Here, a new method for the generation of DNA fragments called AFLP (amplified fragment length polymorphism) was investigated for its ability to distinguish 19 of the major strawberry cultivars grown in the United States and to assess the genetic relationships of the cultivars. The AFLP fragments generated from any one set of reactions were more than sufficient to distinguish all the 19 cultivars demonstrating the effectiveness of AFLPs for fingerprinting purposes. The AFLP fragments, however, did not prove as useful for assessing the genetic relationships of the cultivars. Genetic relationships determined from the AFLP data did not correspond to relationships determined from another DNA marker system called RAPD (randomly amplified polymorpic DNA) or to pedigree information. This information is critical to scientists attempting to develop reliable fingerprinting methods and accurate measures of genetic relatedness for use by breeders and the nursery industry.
Nineteen of the major strawberry (Fragaria x ananassa Duch.) cultivars grown in the United States and Canada were examined for AFLP marker polymorphisms. For the AFLP reactions, the EcoRI-ACC primer was used in combination with four MseI primers (MseI-CAC, MseI-CAG, MseI-CAT, or MseI-CTT). Each set of primers produced 42-54 scorable polymorphic fragments ranging in size between 50 and 500 bp. The polymorphic fragments produced from each set of primers were more than sufficient to distinguish among all the cultivars, demonstrating the usefulness of AFLP markers for cultivar identification. Similarity coefficients were calculated based on data from 228 AFLP markers and data from 15 previously characterized RAPD markers. The RAPD markers had been specifically selected for fingerprinting purposes because they succesfully distinguish 41 strawberry cultivars, including the 19 cultivars analyzed in this study. Separate dendrograms were constructed based on analysis of the AFLP and RAPD marker data using the unweighted pair group method of arithmetic averages (UPGMA). Correlations between similarity coefficients calculated from AFLP marker data, similarity coefficients calculated from RAPD marker data, and coefficients of coancestry calculated from pedigree information were evaluated. Interestingly, a better correlation with the coefficients of coancestry was observed with the RAPD marker data than with the AFLP marker data.