DIRECT COMPARISON OF LEVELS OF GENETIC-VARIATION AMONG BARLEY ACCESSIONS DETECTED BY RFLPS, AFLPS, SSRS AND RAPDS

RFLPs, AFLPs, RAPDs and SSRs were used to determine the genetic relati onships among 18 cultivated barley accessions and the results compared to pedigree relationships where these were available. All of the appr oaches were able to uniquely fingerprint each of the accessions. The f our assays differed in the amount of polymorphism detected. For exampl e, all 13 SSR primers were polymorphic, with an average of 5.7 alleles per primer set, while nearly 54% of the fragments generated using AFL Ps were monomorphic. The highest diversity index was observed for AFLP s (0.937) and the lowest for RFLP (0.322). Principal co-ordinate analy sis (PCoA) clearly separated the spring types from the winter types us ing RFLP and AFLP data with the two-row winter types forming an interm ediate group Only a small group of spring types clustered together usi ng SSR data with the two-row and six-row winter varieties more widely dispersed. Direct comparisons between genetic similarity (GS) estimate s revealed by each of the assays were measured by a number of approach es. Spearman rank correlation ranked over 70% of the pairwise comparis ons between AFLPs and RFLPs in the same order. SSRs had the lowest val ues when compared to the other three assays. These results are discuss ed in terms of the choice of appropriate technology for different aspe cts of germplasm evaluation.