DETECTION OF ALIEN CHROMATIN CONFERRING RESISTANCE TO THE BEET CYST-NEMATODE (HETERODERA-SCHACHTII SCHM) IN CULTIVATED BEET (BETA-VULGARIS L) USING IN-SITU HYBRIDIZATION

Chromatin originating from wild beets of the genus Beta, section Procu mbentes, has been investigated in nematode-resistant hybrid-derived li nes of sugar beet (Beta vulgaris L.) by in situ hybridization using sa tellite, telomeric and ribosomal DNA repeats, a yeast artificial chrom osome (YAC) and total genomic DNA as probes. The alien chromosome was detected in three monosomic addition lines (2n = 18 + 1) by genomic in situ hybridization, Fluorescence in situ hybridization with a genome- specific satellite repeat and YAC DNA enabled the visualization of Pro cumbentes chromosomes, and in double-target hybridization it was shown that they do not carry 18S-5.8S-25S rRNA and 5S rRNA genes. The wild beet-specific satellite repeat and the telomere sequence from Arabidop sis thaliana were used to perform a structural analysis of the wild be et chromosome fragments of two resistant fragment addition lines. It w as shown that one physical end of the chromosome fragments consists of telomeric repeats, Comparison of fragment sizes indicated that the sm all chromosome fragments harbouring the resistance gene most likely re sulted from the loss of one wild beet chromosome arm and an internal d eletion of the remaining arm.