It has been claimed that the system that delivers the products of plant breeding reduces the diversity of cultivated varieties, leading to increased genetic vulnerability. The objective of our study was to monitor the temporal trends in genetic diversity over the past five decades among maize cultivars with the largest acreage in Central Europe. Thirty individuals of five prominent open-pollinated varieties (OPVs) from Central Europe, 85 maize hybrids of economic importance, and their dent and flint parental components were examined with 55 SSRs. The genetic variation within and among varieties decreased significantly during the five decades. The five OPVs contain numerous unique alleles that were absent from the elite flint pool. Consequently, OPVs could represent useful sources for broadening the genetic base of elite maize breeding germplasm.