LOW-LEVEL OF POLYMORPHISM DETECTED BY SSR PROBES IN BREAD WHEAT

In-gel hybridization patterns were studied in a set of nine diverse br ead wheal (Triticum aestivum L. em. Thell) genotypes using 23 simple s equence repeat (SSR) probes in combination with 14 different restricti on enzymes. Multilocus fingerprints due to SSR probes, shown earlier t o be characteristic of a majority of plant genomes, were not obtained and only a very low level of polymorphism was detected when using as m any as 142 probe-enzyme combinations. The hybridization of a prominent solitary high molecular weight fragment (>23 kb) with a number of SSR probes suggested the presence of these SSRs (microsatellites) within the long stretches of repeated DNA sequences. This indicates that the genome of bread wheat differs from that of other plants in the organiz ation and distribution of SSRs and that SSR probes detect very little polymorphism.