Insights Into Sequences of Viral and Bacterial Origin in the Metatranscriptome of Centaurea cyanus L. Susceptible and Resistant to Acetolactate Synthase (ALS)-Inhibiting Herbicides.

Cornflower (Centaurea cyanus L.) is a widespread weed in cereal crops and is commonly controlled with sulfonylurea herbicides. In Poland, populations of cornflower resistant to acetolactate synthase inhibiting herbicides, such as tribenuron-methyl, have been increasingly reported. Both target-site and non-target-site resistance mechanisms may contribute to this phenomenon. Plant-associated microorganisms are known to play essential roles in alleviating abiotic stress. Moreover, weeds are considered reservoirs of plant pathogenic viruses. Since bacteria and viruses associated with cornflower have not been analysed to date, data mining was undertaken to identify viral and bacterial sequences in metatranscriptome datasets obtained from plant biotypes that are both susceptible and highly resistant to tribenuron-methyl. Using MEGAN6 and Kraken2, taxonomic classification revealed the presence of sequences of two double-stranded RNA viruses belonging to the family Partitiviridae, which have not been described before. For bacterial sequences, 19 genera were identified, including Bacillus, Mesorhizobium and Acinetobacter, some of which are associated with plant growth promotion or xenobiotic degradation. Although the presence of partitiviruses was unrelated to herbicide resistance status, some bacterial genera (e.g., Rothia) were more abundant in resistant than in susceptible plants. These results suggest that those bacterial genera present in weeds may be involved in counteracting ALS-inhibiting herbicides.