STUDY OF MICROSPORE-CULTURE RESPONSIVENESS IN OILSEED RAPE (BRASSICA-NAPUS L) BY COMPARATIVE MAPPING OF A F2 POPULATION AND 2 MICROSPORE-DERIVED POPULATIONS

RFLP segregation analyses were performed on a F-2 population and two F-1 microspore-derived populations from the same cross between a microspore culture-responsive parent ('Topas') and a non-responsive parent ('Westar'). A total of 145 loci were detected with 87 cDNA clones. Eighty-two markers were common across all three populations. A total of 66 markers was assembled into 18 linkage groups and 16 markers remained unlinked. Segregation distortions were significant for 29% of the markers in the F-2 population and 23% and 31% in microspore-derived populations M3 and M5, respectively. An equivalent number of markers showed biased segregation towards each parental allele in the F-2 population while more markers showed a significant deviation from the expected Mendelian ratio towards the responsive parent in both microspore-derived populations. Different subsets of markers showed segregation distortions in the three populations indicating that the selective pressures leading to microspore-derived plants are different from those acting during selfing of the F-1. Linkage groups 1 and 18 were identified as putative chromosomal regions associated with microspore-culture responsiveness.