Using molecular markers for characterizing and preserving germplasm resources.

Molecular markers have revolutionized and modernized our ability to characterize genetic variation and to rationalize genetic selection, being effective and reliable tools for the analysis of genome architectures and gene polymorphisms in crop plants. The area of plant genomics that has shown the greatest development with respect to the use of molecular marker technology is that of population genetics. All DNA polymorphism assays have proven to be powerful tools for characterizing and investigating germplasm resources, genetic variation and differentiation of populations, on the basis of gene diversity and gene flow estimates. In the last decade, RFLP and PCR-derived molecular markers have also been extensively applied in plant genetics and breeding for Mendelian gene tagging and QTL mapping. As a matter of fact, the number of loci for which DNA-based assays have been generated has increased dramatically, the majority using PCR as methodology platform. The information acquired is now being exploited to transfer different traits, including biotic stress resistances and improved quality traits, to important varieties by means of marker-assisted selection (MAS) programs. Although the potential for take-up is now much wider than in the past, the progress seems nevertheless to be slow, albeit measurable. The most important challenges in the near future are certainly the molecular characterization of germplasm collections for preserving them from genetic erosion and the identification of phenotypic variants potentially useful for breeding new varieties. Knowing the presence of useful traits, genes and alleles would help in making decisions on the multiplication of plant accessions and the maintenance of seed stocks. There are no doubts that the use of molecular markers for characterization and conservation of genetic resources should be implemented so that potentially useful genes and genotypes can be added to core collections to make them exploitable by breeders. A new concept that might be successful is that of building crop plant collections primarily based on the knowledge of the presence of valuable genes and traits.