Identification and characterization of genic microsatellites in Cunninghamia lanceolata (Lamb.) Hook (Taxodiaceae)

Abstract

Genomic resources for conventional breeding programs are extremely limited for coniferous trees, and existing simple sequence repeat markers are usually identified through the laborious process of hybridization screening. Therefore, this study aimed to identify gene-based microsatellites in the Chinese fir, Cunninghamia lanceolata (Lamb.) Hook by screening transcript data. We identified 5200 microsatellites. Trinucleotide motifs were most common (47.94%) and were followed by tetranucleotide motifs (24.92%). The AG/CT motif (43.93%) was the most abundant dinucleotide repeat, whereas AAG/CTT (25.07%) was the most common trinucleotide repeat. A total of 411 microsatellite primer pairs were designed and 97 polymorphic loci were identified by 8 genotypes. The number of alleles per locus (Na) in these polymorphic loci ranged from 2 to 5 (mean, 2.640), the H_o values were 0.000-1.000 (mean, 0.479), and the H_E values were 0.125-0.775 (mean, 0.462). The polymorphic information content (PIC) values were 0.110-0.715 (mean, 0.383). Seventy-two of the 97 polymorphic markers (74.23%) were present within genes with predicted functions. In addition, in genetic diversity and segregation analyses of 16 genotypes, only 5.88% of the polymorphic loci displayed segregation distortion at the p<0.05 level. Transferable amplification of a randomly selected set of 30 genic microsatellites showed that transferability decreased with increasing evolutionary distance between C. lanceolata and target conifers. Thus, these 97 genic markers will be useful for genetic diversity analysis, germplasm characterization, genome mapping and marker-assisted breeding in C. lanceolata, and evolutionary genetic analysis in Taxodiaceae.