MAPPING LOCI CONTROLLING VERNALIZATION REQUIREMENT AND FLOWERING TIMEIN BRASSICA-NAPUS

Rapeseed cultivars (Brassica napus L.) can be classified into annual a nd biennial groups according to their requirement for vernalization in order to induce flowering. The genetic control of these phenotypic di fferences is not well understood, but this information could be valuab le for the design of breeding approaches to accelerate rapeseed improv ement. In order to map loci controlling this variation, a doubled hapl oid population, derived from a cross between annual and biennial culti vars, was evaluated for vernalization requirement and days-to-flowerin g in a replicated field experiment using three treatments: no vernaliz ation, 4 weeks of vernalization and 8 weeks of vernalization. A linkag e map of 132 RFLP loci was used to locate loci controlling these trait s. Marker segregation in one region of linkage group 9 was strongly as sociated with the annual/biennial growth habit in the unvernalized tre atment and with days-to-flowering in all three treatments. Two other r egions with smaller effects on days-to-flowering were also identified.