AFLP marker polymorphism in cucumber (Cucumis sativus L.) near isogenic lines differing in sex expression.

The AFLP technique was used to evaluate the level of polymorphism between two pairs of isogenic cucumber (Cucumis sativus L.) lines (NIL) differing in flower sex expression. The BSA techniques were also applied to find molecular markers linked to sex determination genes (dominant alleles) in those cucumber lines. Sex determination in cucumber is controlled by three main loci F, M and Gy. The interaction of these loci is responsible for the formation of the various phenotypes of flowers in respect to sex in the analyzed lines [corrected]. A female line 2gg with a ff/MM/gygy genotype, isogenic to a monoecious line B10 (genotype ff/MM/GyGy), and a female line Gy3 with a FF/MM/GyGy genotype, isogenic to a hermaphroditic line HGy3 (genotype FF/mm/GyGy). Using 56 combinations of AFLP primers, used for the analysis of lines 2gg and B10, gave 3794 bands, of which 155 (4.1%) were polymorphic. Ten bands distinguished gynoecious and monoecious bulks appearing at the same time in the appropriate parent; they are believed to be linked to the Gy locus. The isogenic lines Gy3 and HGy3 showed a higher level of polymorphism (14.2%). In this case, 55 combinations of primers gave 2996 reaction products, of which 430 showed variation. Twenty bands occurred in one bulk and in one parent, so they are probably associated with the M locus. Using the AFLP technique, the isogenicity of the lines was evaluated. The level of polymorphism (per pair of primer) between lines 2gg and B10 is 0.072% and is four times lower than that between the Gy3 and HGy3 lines (0.27%). The differences in the isogenicity of the lines can result from the degree of their relatedness, which may reflect the way they were derived.