A CHROMOSOME-SPECIFIC DNA-SEQUENCE WHICH REVEALS A HIGH-LEVEL OF RFLP IN WHEAT

An unusual genomic DNA clone, PSR454, was isolated from a partial genomic library of wheat. This sequence is moderately repeated and detects at least 30 related sequences, all located in a tight linkage block on the long arm of chromosome 3B. When used as a RFLP probe, PSR454 detects a high level of polymorphism between wheat varieties that carry the sequence. There is no detectable hybridisation to sequences in one-third of the varieties tested, providing an "on-off" polymorphism that can be detected on dot blots, rather than the more resource-consuming conventional Southern analysis.