Utilization of doubled haploid technique in Brassica rapa population improvement

Abstract

The utilization of doubled haploid (DH) plants in population improvement of Brassica rapa was studied by randomly intercrossing 4, 8, 12 and 22 DH lines developed from the B. rapa cultivar Reward and the B. rapa breeding line DSC3 for two generations to constitute synthetic populations. The synthetic populations and the DH plants used in their formation were evaluated for agronomic performance at two locations in the field in 1996 and for genetic variation using random amplified polymorphic DNA (RAPD) analysis. Intercrossing as few as four DH lines from the breeding line DSC-3 produced a synthetic population with improved performance over that of the contributing DH lines. The synthetic population produced from the interpollination of eight DH lines showed an agronomic performance over that of the contributing DH lines to a level similar to the Reward donor population. RAPD analysis efficiently characterized the genotypic variation present in DH lines and synthetic populations, detecting 22–72% polymorphism between DH lines, 17–53% and 27–47% polymorphism in the first and second synthetic populations, respectively. This characterization may be useful as a tool in the reestablishment of heterogeneity and recovery of agronomic performance in B. rapa synthetic populations derived from DH lines by determining the level of genetic variability among DH lines and therefore optimal population size. Key words: Brassica rapa, synthetic population, doubled haploids, RAPD, agronomic performance