Genetic diversity and relationships based on isozymes were studied in 31 ac
cessions of turnip (Brassica rapa L. var. rapa). The material included vari
eties, elite stocks, landraces and older turnip of slash-and-burn type from
the Nordic area. A total of 9 isozyme loci and 26 alleles were studied. Th
e isozyme systems were ACO, DIA, GPI, GOT, PGM, PGD and SKD. The level of h
eterozygosity was reduced in the landraces. but it was high for the variety
group 'Ostersundom'. Turnip has a higher genetic variation than other crop
s within B. rapa and than in other species with the same breeding system. T
he genetic diversity showed that 18.7 % of the genetic variation was within
the accessions, and the total H-T value was 0.358. Gpi-1 and Pgd-1 showed
the lowest variation compared with the other loci, The cluster analysis rev
ealed five clusters, with one main cluster including 25 of the 31 accession
s. The dendrogram indicated that the variety group 'Ostersundom' clustered
together whereas the variety group 'Bortfelder' was associated with country
of origin. The landraces were spread in different clusters. The 'slash-and
-burn' type of turnip belonged to two groups.