Applying meta-data of soybean grain in origin trace and quarantine inspection.

Soybean and derived products are among the most important food for both humans and animals. China is the world's largest importer of soybeans, with more than 100 million tons of annual imports, mainly from the United States of America (US), Brazil, and Argentina. However, there have been limited studies on the microbiota associated with imported soybean grains. Here, we reveal the soybean microbiota using amplicon sequencing based on samples from four countries on three continents of North America (US), South America (Argentina, Brazil), and Asia (China). Our results showed that the soybean-associated microbiota from different continents significantly separated, presenting strong geographic variations. The core microbial taxa and geographically specified taxa were defined, with Alternaria, Enterobacter, Plectosphaerella, Stenotrophomanas, and Xeromyces defined as the core microbiota for soybean from Asia; Amanita, Aspergillus, Fusarium, Nigrospora, Herbiconiux, Pseudomonas, Saccharopolyspora, and Schumannella from North America; and Bradyrhizobium, Colletotrichum, Filobasidium, Phialosimplex, Mycosphaerella, Septoria, Sphingomonas, and Weissalla, from South America. In addition, we build the Random Forest (RF) model to predict the source of imported soybean grains. We could accurately predict the original countries of imported soybean grains within the RF prediction models, with accuracies greater than 95 %. We constructed a database of soybean-related quarantine pathogens using full-length sequences of fungal ITS region and bacterial 16S rDNA region. Two phytopathogenic fungi, Diaporthe caulivora and Cladosporium cucumerinum, listed in the Chinese quarantine catalog, were intercepted through metabarcoding sequencing. The former was further confirmed using an available national standard protocol of qPCR diagnosis. In summary, our NGS-based approach revealed the microbiota associated with soybeans. It could provide comprehensive information and valuable method on the trace the origin of soybean and detection of quarantine pathogens at Customs and departments of inspection and quarantine.