Growth and yield of doubled haploid lines of oilseed Brassica rapa

The production of doubled haploid (DH) lines of Brassica rapa could be an e fficient procedure for the development of inbred parents for hybrid product ion. A total of 162 B. rapa DH lines were evaluated in field tests at Saska toon, Canada, in single row, replicated tests and 10 DH lines were tested i n four-row plot, multilocation, replicated tests. Seed of DH lines was prod uced by bud selfing in the greenhouse. Approximately one-fifth of all DH li nes tested were chlorophyll deficient, presumably due to the expression of recessive alleles. Inbreeding depression was evident in low seed and biolog ical yields, low number of seeds per pod and delayed flowering. Seed yield of DH lines was positively associated with the number of seeds per pod, ear ly flowering and a long pod-filling period. One DH line was equal in yield to its donor population (DP), suggesting that dominance deviation was the g enetic basis for high seed yield in this species. The consistent performanc e of DH lines over years and locations indicated that DH lines may be selec ted after 1 year of evaluation for combining ability testing. Higher yieldi ng DH lines of B. rapa must be selected before they can be used as parents for hybrid development.