Microsatellite Genetic Diversity Analysis and Allelic Variation Comparison of Obsolete and Modern Bulgarian Bread Wheat (Triticum aestivum L.) Varieties

A set of 24 microsatellite markers was used for assessing the genetic diversity of 40 obsolete and modern Bulgarian winter wheat (Triticum aestivum L.) varieties. The total number of alleles detected was 215 with the average per locus 8.96 and varying from 4 (Xgwm480, Xgwm333) to 15 (Xgwm291). The obsolete varieties of interest were created in the period between 1911 and 1938 through selection of local populations, originating from three Bulgarian regions. The number of alleles detected in those old varieties was 182 with an average of 7.58, out of which 2.67 were rare. Regional differences in the allelic richness and diversity were also observed. Greater number of alleles was found in the old varieties, originating from South Bulgarian and Northeast landraces. Modern wheat breeding in Bulgaria has led to a decrease in the alleles per locus ratio and an increase in the allelic frequency. The same process has invalidated 44.2% of the old wheat alleles, preserved 40.9% and made possible an inflow of 14.9% new alleles. The artificial selection tolerated the preservation of a big number of the alleles of some loci found in old varieties (Xgwm205 and Xgwm160), while others experienced loss of alleles (Xgwm291, Xgwm312, Xgwm219 and Xgwm261). The genealogical analysis of 94 Bulgarian varieties, created in the period 1940–2000, showed that 27.7% of those varieties were based on Bulgarian landraces.