Large scale development of selectively amplified microsatellite polymorphic loci (SAMPL) markers in spruce (Picea)

Basic concepts and methodologies of DNA marker systems in plant molecular breeding

The concepts, methodologies and applications of some of the major molecular or DNA markers commonly used in plant science have been presented. The general principles of molecular marker techniques have been elucidated with detailed explanation of some notable basic concepts associated with marker applications: marker polymorphism, dominant or co-dominant mode of inheritance, agronomic trait-marker linkage, genetic mutations and variation. The molecular marker methods that have been extensively reviewed are RFLP, RAPD, SCAR, AFLP, SSR, CpSSR, ISSR, RAMP, SAMPL, SRAP, SSCP, CAPS, SNP, DArT, EST, and STS. In addition, the practicality of the retrotransposon-based marker methods, IRAP, REMAP, RBIP, and IPBS, have been discussed. Moreover, some salient characteristics of DNA markers have been compared and the various marker systems classified as PCR- or non-PCR-based, dominantly or co-dominantly inherited, locus specific or non-specific as well as at the levels of marker polymorphism and efficiency of marker reproducibility. Furthermore, the principles and methods of the following DNA markers have been highlighted: Penta-primer amplification refractory mutation system (PARMS), Conserved DNA-Derived Polymorphism (CDDP), P450-based analogue (PBA) markers, Tubulin-Based Polymorphism (TBP), Inter-SINE amplified polymorphism (ISAP), Sequence specific amplified polymorphism (S-SAP), Intron length polymorphisms (ILPs), Inter small RNA polymorphism (iSNAP), Direct amplification of length polymorphisms (DALP), Promoter anchored amplified polymorphism (PAAP), Target region amplification polymorphism (TRAP), Conserved region amplification polymorphism (CoRAP), Start Codon Targeted (SCoT) Polymorphism, and Directed Amplification of Minisatellite DNA (DAMD). Some molecular marker applications that have been recently employed to achieve various objectives in plant research have also been outlined. This review will serve as a useful reference resource for plant breeders and other scientists, as well as technicians and students who require basic know-how in the use of molecular or DNA marker technologies.

A high-density genetic linkage map of a black spruce (Picea mariana) × red spruce (Picea rubens) interspecific hybrid

Genetic maps provide an important genomic resource of basic and applied significance. Spruce (Picea) has a very large genome size (between 0.85 × 1010 and 2.4 × 1010 bp; 8.5-24.0 pg/1C, a mean of 17.7 pg/1C ). We have constructed a near-saturated genetic linkage map for an interspecific backcross (BC1) hybrid of black spruce (BS; Picea mariana (Mill.) B.S.P.) and red spruce (RS; Picea rubens Sarg.), using selectively amplified microsatellite polymorphic loci (SAMPL) markers. A total of 2284 SAMPL markers were resolved using 31 SAMPL-MseI selective nucleotide primer combinations. Of these, 1216 SAMPL markers showing Mendelian segregation were mapped, whereas 1068 (46.8%) SAMPL fragments showed segregation distortion at α = 0.05. Maternal, paternal, and consensus maps consistently coalesced into 12 linkage groups, corresponding to the haploid chromosome number (1n = 1x = 12) of 12 in the genus Picea. The maternal BS map consisted of 814 markers distributed over 12 linkage groups, covering 1670 cM, with a mean map distance of 2.1 cM between adjacent markers. The paternal BS × RS map consisted of 773 markers distributed over 12 linkage groups, covering 1563 cM, with a mean map distance of 2.0 cM between adjacent markers. The consensus interspecific hybrid BC1 map consisted of 1216 markers distributed over 12 linkage groups, covering 1865 cM (98% genome coverage), with a mean map distance of 1.5 cM between adjacent markers. The genetic map reported here provides an important genomic resource in Picea, Pinaceae, and conifers.

Near-saturated and complete genetic linkage map of black spruce (Picea mariana)

Background

Genetic maps provide an important genomic resource for understanding genome organization and evolution, comparative genomics, mapping genes and quantitative trait loci, and associating genomic segments with phenotypic traits. Spruce (Picea) genomics work is quite challenging, mainly because of extremely large size and highly repetitive nature of its genome, unsequenced and poorly understood genome, and the general lack of advanced-generation pedigrees. Our goal was to construct a high-density genetic linkage map of black spruce (Picea mariana, 2n = 24), which is a predominant, transcontinental species of the North American boreal and temperate forests, with high ecological and economic importance.

Results

We have developed a near-saturated and complete genetic linkage map of black spruce using a three-generation outbred pedigree and amplified fragment length polymorphism (AFLP), selectively amplified microsatellite polymorphic loci (SAMPL), expressed sequence tag polymorphism (ESTP), and microsatellite (mostly cDNA based) markers. Maternal, paternal, and consensus genetic linkage maps were constructed. The maternal, paternal, and consensus maps in our study consistently coalesced into 12 linkage groups, corresponding to the haploid chromosome number (1n = 1x = 12) of 12 in the genus Picea. The maternal map had 816 and the paternal map 743 markers distributed over 12 linkage groups each. The consensus map consisted of 1,111 markers distributed over 12 linkage groups, and covered almost the entire (> 97%) black spruce genome. The mapped markers included 809 AFLPs, 255 SAMPL, 42 microsatellites, and 5 ESTPs. Total estimated length of the genetic map was 1,770 cM, with an average of one marker every 1.6 cM. The maternal, paternal and consensus genetic maps aligned almost perfectly.

Conclusion

We have constructed the first high density to near-saturated genetic linkage map of black spruce, with greater than 97% genome coverage. Also, this is the first genetic map based on a three-generation outbred pedigree in the genus Picea. The genome length in P. mariana is likely to be about 1,800 cM. The genetic maps developed in our study can serve as a reference map for various genomics studies and applications in Picea and Pinaceae.