FISH for localization of two repeat families on Beta Procumbentes chromosomes and exended DNA filbres in a series of monosomic additions

The physical localization and organization of two Procumbentes specific repetitive DNA sequences, PB6-4 and OPX2, on the chromosomes of  B.procumbe were demonstrated by multi-color fluorescence in situ hybridization (FISH) , using the species itself and a set of B. procumbens derived monosomic addition families in B.vulagris. FISH to miototic metaphase chromosome spreads of B. procumbentes revealed that probe PB6-4 predominantly occurred in the centromere region of all chromosomes, with substantial differences in the number of sites per chromosome. However, the repeat OPX2 showed a dispersed distribution, with different hybridization patterns for each of the chromosomes. Somultaneous hybridization with PB6-4 and OPX2 to miotic chromosomes of the B.procumbens derived monosomic additions revealed that the fluorescent signals were confined to one of the 19chromosomes, indication that no cross-hybridization  with the genome of B. vulgaris occurred. The simplified situation of FISH signals on a single chromosome permitted to establish the distribution patterns of both repeats for each of the individual B. procumbens chromosomes in the background of  B. vulgaris. A FISH karyotype of the species was constructed. On the basis of known linkage of the repeat P B 6-4 with the locus Hs1pro-1 for beet cyst nematode resistance, it was concluded that this locus is likely to be located in the centromere region of chromosome 1.the results were also in agreement with the conclusion of previsun molecular studies, which led to renaming of some addition families of B. procumbens .FISH of PB6-4 to extended DNA fibers of eight different B. procumbens derived monosomic additions indicated that each alien chromosome has a different number of PB6-4 copies, and  that  the  arrays  have  different  sizes  and  very  in  number  among  the  alien  chromosomes. The power of both FISH techniques for the molecular analysis of the monosomic additions is discussed.