Plant Genome IV Conference Plant Genome IV Conference
Hexaploid bread wheat (Triticum aestivum) as an inbreeding crop plant exhibits an extremely low level of intraspecific polymorphism with RFLP markers. To circumvent this problem, we are currently developing PCR-based microsatellite markers based on dinucleotide repeats (CA and CT). So far, more than 700 clones containing such repeats have been sequenced. For more than 350 microsatellite containing clones, PCR primers have been designed. Approximately 60% of primer pairs are functional insofar as they amplify PCR products of the expected fragment size. 40% of the primer pairs do not result in the correct product sizes or result in multiple fragments and, thus, are not useful for genetic analysis. Assignment of the functional microsatellite markers to chromosomes by means of cytological stocks of Chinese Spring show that in contrast to RFLPs, microsatellite markers are usually specific for a given genome (A, B or D). A comparison to RFLP markers reveals that microsatellite markers, with up to 16 alleles in breeding lines, are much more variable in wheat. We were able to discriminate a set of 35 recent European wheat cultivars by the use of only 23 microsatellite markers. In contrast to RFLP markers, wheat microsatellite markers are only of limited use in related species such as barley and rye, because of the high primer specificity. However, they can be used in the wheat progenitors T. durum (AABB), T. monococcum (AA) or T. tauschii (DD). Due to their PCR-based nature, microsatellite markers are amenable to automatization and can be detected by the use of automated DNA sequencers or by silver staining of sequencing gels and require only small amounts of genomic DNA as starting material.