Isolation and characterization of microsatellite markers for Osmanthus fragrans (Oleaceae) using 454 sequencing technology

Osmanthus fragrans (Oleaceae) is an evergreen shrub or small tree that grows in south China. In this study, Roche 454 FLX+ sequencing combined with the magnetic bead enrichment method was used to isolate microsatellite markers from the genome of O. fragrans. A total of 1471 microsatellites that contained enough flanking sequences for primer pair design were identified from 89,633 raw sequencing reads. One hundred primer pairs were randomly chosen to test primer amplification efficiency. Among these tested primer pairs, 20 yielded polymorphic amplification products across 16 individuals from the Albus, Luteus, and Aurantiacus groups. The number of alleles ranged from 2 to 6, with an average of 3.7. The observed heterozygosity ranged from 0 to 0.813, with an average of 0.460. Shannon's information index ranged from 0.463 to 1.707, with an average of 0.975. Six loci (Of 05, Of 06, Of 08, Of 12, Of 15, and Of 19) deviated significantly from Hardy-Weinberg equilibrium (P < 0.05), which was due to an excess of homozygotes or heterozygotes. Nine pairs of loci (Of 01 and Of 05; Of 04 and Of 05; Of 01 and Of 06; Of 04 and Of 12; Of 02 and Of 13; Of 04 and Of 13; Of 12 and Of 13; Of 04 and Of 19; Of 05 and Of 19) showed significant linkage disequilibrium, which indicated significant allelic association between the loci. This set of microsatellite markers will be valuable for molecular marker-assisted breeding in O. fragrans.