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 micros pore culture-responsive parent ('Topas') and a non-responsive parent ( 'Westar'). A total of 145 loci were detected with 87 cDNA clones. Eigh ty-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 mark ers in the F-2 population and 23% and 31% in microspore-derived popula tions 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 Me ndelian ratio towards the responsive parent in both microspore-derived populations. Different subsets of markers showed segregation distorti ons in the three populations indicating that the selective pressures l eading to microspore-derived plants are different from those acting du ring selfing of the F-1. Linkage groups 1 and 18 were identified as pu tative chromosomal regions associated with microspore-culture responsi veness.