SSR MARKERS IN GENETIC DIVERSITY ASSESSMENT OF CROP VARIETAL COLLECTIONS: MOLECULAR BASES AND PRACTICAL APPLICATIONS

Abstract

Simple Sequence Repeat (SSR) markers – tandem repeats of 1–6 nucleotide motifs – exhibit high polymorphism generated by replication slippage and unequal crossing-over, with mutation rates of 10⁻⁴–10⁻² per locus per generation. The multi-allelic nature and codominant inheritance of SSR loci provide exceptional discriminatory power in variety identification, pedigree analysis, and genetic purity control. This review examines the molecular principles of SSR polymorphism, characterizes key information content parameters including polymorphic information content (PIC) and expected heterozygosity (He), and systematizes data on SSR marker applications in genetic diversity assessment of varietal collections of cereals (wheat, rice, maize), legumes, and clonally propagated crops (cacao, potato). Particular attention is given to SSR capabilities in molecular barcoding, core collection construction, and genetic erosion monitoring in genebanks. Empirical data consistently demonstrate that 7–11 times more SNP loci are required to achieve equivalent precision in genetic distance estimation compared to SSR markers. This ratio defines the context-dependent advantages of microsatellite markers: maximum discriminatory power with a minimum number of typed loci is indispensable for variety identification, pedigree verification, and seed quality control. Prospects for integrating SSR technologies with genotyping-by-sequencing platforms and machine learning algorithms in genetic resource management systems are discussed.