Furthermore, the application of molecular marker technology enables differences in gene sequence to be directly observed and described. Molecular or DNA markers also aid in the introduction of desirable traits from wild relatives to cultivated species by providing vital phylogenetic information. Molecular marker systems have also facilitated the assembly of genetic maps and speed plant breeding by marker assisted-selection ( Jiang, 2013 Collard et al., 2005). DNA markers have been very valuable in revealing the extent and distribution of variation in a diversity of crop species ( Hailu and Asfere, 2020) and aiding tremendously in different plant germplasm conservation and management. Current rapid advances in molecular marker technology have produced novel techniques that are greatly facilitating research in almost every sphere of crop development and improvement. Moreover, advances in different aspects of plant genetics have enhanced deeper insight into molecular markers, plant species genetic diversity and tremendously aided the success of plant molecular breeding. In some cases, the distance between the termini sequences altered by insertion or deletion mutation events could lead to polymorphism.ĭNA marker protocols mediated by PCR applications have become commonly used in plant genomic analysis. Genetically, genotypes exhibit contrasting pool of fragments as a result of point mutations in oligonucleotide priming sites. These markers are mainly nucleic acids that are polymorphic among individuals or populations ( Collard et al., 2005). Molecular markers constitute very useful tools currently available for research in plant improvement. The PCR technique enables specific DNA sequences to be practically amplified from genomic DNA sections using specific or arbitrary designed oligonucleotide primers. Since then, the applications of many molecular markers have been reported in various aspects of plant molecular breeding and genomics ( Nadeem et al., 2018). This landmark in plant genomic research was followed by the achievement of PCR-based DNA markers a decade on. The era of molecular marker development and applications begun in the 1980s. 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. Some molecular marker applications that have been recently employed to achieve various objectives in plant research have also been outlined. 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). 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. In addition, the practicality of the retrotransposon-based marker methods, IRAP, REMAP, RBIP, and IPBS, have been discussed. 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. 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 concepts, methodologies and applications of some of the major molecular or DNA markers commonly used in plant science have been presented.
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