Phylogeny of a subset of cassava NBS-LRR proteins with functional resistance genes from other species. Phylogenetic analysis of the NBS domain was carried out by the Maximum likelihood method using cassava NBS-LRR proteins as well as cloned functional R genes from different species including Arabidopsis, rice, and more (Additional file 3). For ease of visualization, we only used a subset of cassava genes that represents each clade (see Additional file 6 for the full tree). Red, green, purple, and blue represent TIR, RPW8, CNL-2, and CNL1 clades, respectively. The bottom clade in the CNL1-1b group is compressed, because it groups resistance proteins that are specific to grasses and does not cluster together with any cassava NBS-LRR protein. Members of this clade include Pi genes from Oryza sativa, Lr genes from Triticum aestivum, and Mla genes from Hordeum vulgare, for example.