Whole genome assembly and gene annotation of a diploid genotype of Brachiaria ruziziensis (syn. Urochloa ruziziensis)

In this work, we have presented a comprehensive analysis of the molecular mechanism linked to aluminium tolerance in Brachiaria species. By assembling and annotating a diploid genotype of B. ruziziensis we have developed the capability for genomic-based studies of desirable phenotypic traits. Using this resource, we have identified three QTLs associated to root architecture and vigour during Al³⁺ stress in a hybrid population from a high and low tolerant accession. We have also identified a number of genes and molecular responses that impact on different aspects of signalling, cell-wall composition and active transports as a response to aluminium stress. Brachiaria tolerance appears to build in the same genes than in rice. However, we found that external mechanisms such as sequestration of Al³⁺ common in other grasses might be not that important in Brachiaria. Also, contrasting regulation in the same genotype after 8 or 72 hours of Al³⁺ stress of numerous genes involved in RNA translation can explain the different levels of tolerance among different Brachiaria species. The newly annotated draft genome represents an important base upon which study other aspects of Brachiaria biology.