Traceability of the local cultivar 'Caaveiro' in flour mixtures used to produce Galician bread by simple sequence repeats and droplet digital polymerase chain reaction technology

The analysis of simple sequence repeats (SSRs) and of bulk ground samples by droplet digital polymerase chain reaction (ddPCR) was investigated as an alternative to individual kernel testing for assessing the presence of local cultivars in common wheat (Triticum aestivum L.) varietal blends. The recent Protected Geographical Indication (PGI) of 'Pan Galego' (Galician bread) requires that the flour comprise a minimum 25% local wheat cultivars. As a test for compliance with this minimum level, wheat flours were prepared by mixing commercial flours with 0%, 5%, 20%, 25% and 30% 'Caaveiro' and 100% 'Caaveiro' and 100% commercial flours were used as controls. A second analysis was performed with a second set of wheat flours with 5% and 25% 'Caaveiro'. These were mixed with two different commercial flours to assess the potential ability of five SSRs to identify the percentage of 'Caaveiro', constituting the first reference of the use of SSRs in the traceability of specific autochthonous cultivars in flour blends. ddPCR using the QX200 system platform was used to the targeted proportions across the simulated range with two out of five SSRs, indicating that they can be used in the traceability of 'Caaveiro' in mixed flours and breads.