Citrus STMS markers development and mapping

We have isolated and characterised microsatellite loci from citrus, to explore the potential of thes markers for cultivar identification, for genetic diversity evaluation and for genome mapping. Small insert library from an homozygous variety Cleopatra mandarin (Citrus reshni) was enriched for (GA) repeats. 960 clones have been sequenced. Pairs of primers for PCR amplification were designed to the flanking region of 250 microsatellites and until now, 100 have been tested for polymorphism and quality of amplification. Considering , the expected sizes of amplified DNA fragments, interpretable amplification products, mendelian segregation and monolocus position, 40 primers pairs have been used to fingerprint 50 accessions of a wide representation of Aurantioideae sub-family. Amplifications were always succefull for true citrus (Poncirus, Fortunella and Citrus) Severinia buxifolia and Eremocitrus glauca while the other genus have less sucess. Cleopatre and Sunki mandarins, known to be very homozygous with other types of markers (RFLP, isozymes) were characterised by 25% of heterozygous loci. A principal co-ordinate analysis and representation of pairwise distance matrices revealed a genetic diversity structure in accordance with the well known relationship and evolution of citrus genera and species. Otherwise, we have analysed the segregation among an inter-generic backcross progeny and mapped 45 microsatellite loci , in addition with 150 AFLP markers. Utilities of these microsatellites markers in our french genetic research program have been discussed. (Texte intégral)