THE EFFECTS OF NON-HOMOLOGY IN RAPD BANDS ON SIMILARITY AND MULTIVARIATE STATISTICAL ORDINATION IN BRASSICA AND HELIANTHUS

In order to estimate the impact of mis-coding non-homologous, co-migra ting DNA bands as homologous, two sets of data were utilized. Analyses were conducted using three Helianthus species in which each co-migrat ing band had previously been confirmed. Comparisons of the similaritie s between these three Helianthus species using the original 177 RAPD b ands and the corrected, homology verified, 197 RAPD band data set reve aled that the triangular relationship among these three species was al most identical in both data sets. The non-homology errors in the Helia nthanus data sets were found to be random. These random errors merely reduced the absolute similarities, but not the relative similarities n or the relationships among the taxa, in principal-coordinate-analysis ordination. Analyses of RAPDs for the classical Brassica U triangle we re made by inserting random non-homologies for 5, 10, 15 and 20% of th e original 220 RAPD bands. These analyses revealed a progressive decre ase in similarities and less loading on the first two axes in principa l coordinate analysis (PCO). However, the basic U triangle of relation ships among these six Brassica species was maintained. It appears that if errors in homology of co-migrating DNA bands are random, this will have little effect on the relative similarities and on PCO ordination . This helps explain the successful use of RAPDs at the specific level .