ISOLATION AND CHARACTERIZATION OF MICROSATELLITES FROM HEXAPLOID BREAD WHEAT

The development of large panels of simple-to-analyse genetic markers f or tagging agronomically important genes and diversity studies in hexa ploid bread wheat is an important goal in applied cereal genetic resea rch. We have isolated and sequenced over 200 clones containing microsa tellites from the wheat genome and have tested 153 primer pairs for ge netic polymorphism using a panel of ten wheat varieties, including the parents of our main mapping cross. A subset comprising 49 primer pair s detects 76 loci, of which 74 can be unequivocably allocated to one o f the wheat chromosomes. A relatively low frequency of the loci detect ed are from the D genome, and these loci show less polymorphism than t hose from the A and B genomes. Generally, the microsatellites show hig h levels of genetic polymorphism and an average of 3.5 alleles per loc us with an average polymorphism information content (PIG), value of 0. 51. The observed levels of polymorphism are positively correlated with the length of the microsatellite repeats. A high proportion, approxim ately two-thirds, of primer pairs designed to detect simple sequence r epeat (SSR) variation in wheat do not generate the expected amplificat ion products and, more significantly, often generate unresolvable PCR products. In general, our results agree closely with those obtained fr om other recent studies using microsatellites in plants.