Isolation and characterization of microsatellite markers for Dendranthema morifolium (Asteraceae) using next-generation sequencing

Dendranthema morifolium (Asteraceae) is a perennial herbaceous plant native to China. A long history of artificial crossings may have resulted in complex genetic background and decreased genetic diversity. To protect the genetic diversity of D. morifolium and enabling breeding of new D. morifolium cultivars, we developed a set of molecular markers. We used pyrosequencing of an enriched microsatellite library by Roche 454 FLX+ platform, to isolate D. morifolium simple sequence repeats (SSRs). A total of 32,863 raw reads containing 2251 SSRs were obtained. To test the effectiveness of these SSR markers, we designed primers by randomly selecting 100 novel SSRs, and amplified them across 60 cultivars representing five different petal shape groups. Sixteen SSRs were polymorphic with the number of alleles ranging from 6 to 19, and their expected and observed heterozygosities ranging from 0.477 to 0.848, and 0.250 to 0.804, respectively. The polymorphism information content ranged from 0.459 to 0.854 and the inbreeding coefficient ranged from -0.119 to 0.759. An unweighted pair-group method arithmetic average analysis was performed to survey the phylogenetic relationships of these 60 cultivars and five clusters were identified. These markers can be used for investigating genetic relationships and identifying elite alleles through linkage and association analyses.

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.