LONG-RANGE ORGANIZATION OF A SATELLITE DNA FAMILY FLANKING THE BEET CYST-NEMATODE RESISTANCE LOCUS (HS1) ON CHROMOSOME-1 OF B-PATELLARIS AND BETA-PROCUMBENS

New members of a satellite DNA family (Sat-121), specific for wild bee ts of the section Procumbentes of the genus Beta, were isolated. Seque nce analysis showed that the members of Sat-121 fall into two distinct classes. The organization of Sat-121 in the vicinity of a beet cyst n ematode (Heterodera schachtii Schm.) resistance locus (Hs1) in B. pate llaris and B. procumbens was investigated by pulsed-field gel electrop horesis (PFGE) using DNA from a series of resistant monosomic fragment additions, each containing an extra chromosome fragment of B. patella ris chromosome-1 (pat-1) in B. vulgaris. In this way several clusters of Sat-121 flanking the Hs1(pat-1) locus were identified. In nematode resistant diploid introgressions (2n=18), which contain small segments of B. procumbens chromosome-1 (pro-1) in B. vulgaris, only two major Sat-121 clusters were detected near the Hs1(pro-1) locus.