To optimize the application of plant growth-promoting rhizobacteria (PGPR) in field trials, tracking methods are needed to assess their shelf life and to determine the elements affecting their effectiveness and their interactions with plants and native soil microbiota. This work developed a real-time PCR (qtPCR) method which traces and quantifies bacteria when added as microbial consortia, including five PGPR species: Burkholderia ambifaria, Bacillus amyloliquefaciens, Azotobacter chroococcum, Pseudomonas fluorescens, and Rahnella aquatilis. Through a literature search and in silico sequence analyses, a set of primer pairs which selectively tag three bacterial species (B. ambifaria, B. amyloliquefaciens and R. aquatilis) was retrieved. The primers were used to trace these microbial species in a field trial in which the consortium was tested as a biostimulant on two wheat varieties, in combination with biochar and the mycorrhizal fungus Rhizophagus intraradices. The qtPCR assay demonstrated that the targeted bacteria had colonized and grown into the soil, reaching a maximum of growth between 15 and 20 days after inoculum. The results also showed biochar had a positive effect on PGPR growth. In conclusion, qtPCR was once more an effective method to trace the fate of supplied bacterial species in the consortium when used as a cargo system for their delivery.

Over the last new decade, there has been a strong interest in landraces and historical wheat varieties from farmers, manufacturers and consumers. They are agronomically and nutritionally interesting but the supply chain (from seed to end-product) is not solid and traceable. High molecular weight glutenins (HMW-GS) can act as markers to trace the varietal correspondence and to verify the genetic purity of the grain and consequently of the flours, marketed and labeled as mono-varietal. In the present work, HMW-GS of different durum wheat Sicilian landraces (Timilia, Russello, Perciasacchi) and one historical variety Margherito were analyzed. At first, specific protein profiles were assigned to each Sicilian landrace by SDS-PAGE and MALDI-TOF/MS analyses, thanks to the availability of pure seeds. Analysis of the protein profiles were then carried out from random samples of seed batches of the same landraces grown on a farm in South-East Sicily. The results highlighted the presence of different protein bands within the individual seed batches, which are reflected in complex profiles in the corresponding commercial flours labelled as mono-varietal. The bread wheat landrace Maiorca cultivated in the same farm was also found as a contaminant at different percentages in the durum wheat batches. The results of this study offer opportunities to improve the supply chain of the different Sicilian landraces or historical varieties cultivated, underlining the need for accurate controls from the field to the transformation process to be labelled as mono-varietal products.