Genetic Diversity of Local Wheat (Triticum aestivum L.) and Traceability in the Production of Galician Bread (Protected Geographical Indication) by Microsatellites

Galician wheat (Triticum aestivum L.) serves as the foundational component of Galician bread, a traditional Spanish product granted the Protected Geographical Indication (PGI, EU quality scheme), which is primarily conserved at the Agricultural Research Center of Mabegondo (CIAM), Xunta de Galicia, A Coruña, Spain. This study evaluated 20 ecotypes and cultivars, in comparison to 4 Galician wheats and 14 commercial wheat varieties used as references. Seventeen simple sequence repeats (SSRs) were evaluated to elucidate their genetic structure, determine their origins, and differentiate them from commercial cultivars for traceability purposes. In total, 296 wheat plants were analyzed, revealing 156 unique genotypes, 13 of which were from commercial cultivars and 143 of which were from local cultivars and ecotypes. The SSR loci revealed 221 microsatellite alleles, with an average of 11 alleles per locus. Of these, 151 alleles were found in local cultivars and ecotypes, and 134 were present in commercial cultivars, with 65 and 50 alleles exclusive to each group, respectively. A Structure software analysis demonstrated substantial genetic differentiation (Fst = 0.26) between two primary clusters, RPP1 (comprising commercial cultivars, and two ecotypes, 41 and 43) and RPP2 (consisting of local cultivars, elite lines, and ecotypes). Moreover, neighbor-joining tree analysis and principal component analysis (PCA) confirmed the high differentiation between these clusters, highlighting the singularity of Galician wheat, which is useful for the traceability of Galician bread. Furthermore, the SSRs were effective in tracking the use of Galician wheat, which displayed specific Galician alleles, in flour, sourdough, and bread samples, corroborating previous findings even when a greater number of Galician ecotypes were included.