Plant & Animal Genome VI Conference Plant & Animal Genome VI Conference
P54
One hundred and twenty four microsatellite markers developed from a rice genomic library (74 markers) and from cDNA sequences available in public databases (50 markers) were surveyed for amplification in three dicots, namely brassica, tomato and tobacco, and in three monocots, maize, sorghum and wheat. Two rice cultivars, IR 36 and TN 67, were used as controls. Sixty six percent (49/74) of the genomic microsatellites could be amplified in at least one of the species surveyed, but amplification was usually weaker than in rice, indicating the lower sequence homology in the flanking regions. Among them, maize gave the highest amplification rate (66%). Approximately 15% of the rice primers amplified 2 or 3 bands in maize, presumably reflecting the internal duplication of the maize genome during evolution. In sorghum, 53% of primers amplified. Wheat gave the lowest amplification (35%) among the three monocot species and this figure was similar to the amplification rate in dicots. cDNA microsatellites produced a lower frequency of amplification than did genomic microsatellites. For the 50 cDNA primers surveyed, only 16% of them amplified in maize, while in the other five species amplification was less than 5%. To investigate whether microsatellites defined homoeologous segments in rice and maize, markers previously mapped in rice and giving clear amplification in both genera were surveyed for polymorphism and, where possible, mapped in maize. To determine levels of sequence divergence in putatively homologous regions of monocot and dicot genomes, PCR products with clear amplification across genera are being sequenced and the sequence similarity is being compared. The practical application of this study is to determine which microsatellite markers will be useful in constructing a radiation hybrid map of rice.