Genetic diversity of allozymes in turnip (Brassica rapa L. var. rapa) from the Nordic area.

Genetic diversity and relationships based on isozymes were studied in 31 accessions of turnip (Brassica rapa L. var. rapa). The material included varieties, 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. The isozyme systems were ACO, DIA, GPI, GOT, PGM, PGD and SKD. The level of heterozygosity was reduced in the landraces, but it was high for the variety group 'Ostersundom'. Turnip has a higher genetic variation than other crops within B. rapa and than in other species with the same breeding system. The genetic diversity showed that 18.7% of the genetic variation was within the accessions, and the total H tau value was 0.358. Gpi-I and Pgd-I showed the lowest variation compared with the other loci. The cluster analysis revealed five clusters, with one main cluster including 25 of the 31 accessions. 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.