| Summary: | <i>Dalbergioid</i> is a large group within the family <i>Fabaceae</i> that consists of diverse plant species distributed in distinct biogeographic realms. Here, we have performed a comprehensive study to understand the evolution of the nucleotide-binding leucine-rich repeats (NLRs) gene family in <i>Dalbergioids</i>. The evolution of gene families in this group is affected by a common whole genome duplication that occurred approximately 58 million years ago, followed by diploidization that often leads to contraction. Our study suggests that since diploidization, the NLRome of all groups of <i>Dalbergioids</i> is expanding in a clade-specific manner with fewer exceptions. Phylogenetic analysis and classification of NLRs revealed that they belong to seven subgroups. Specific subgroups have expanded in a species-specific manner, leading to divergent evolution. Among the <i>Dalbergia</i> clade, the expansion of NLRome in six species of the genus <i>Dalbergia</i> was observed, with the exception of <i>Dalbergia odorifera,</i> where a recent contraction of NLRome occurred. Similarly, members of the <i>Pterocarpus</i> clade genus <i>Arachis</i> revealed a large-scale expansion in the diploid species. In addition, the asymmetric expansion of NLRome was observed in wild and domesticated tetraploids after recent duplications in the genus <i>Arachis</i>. Our analysis strongly suggests that whole genome duplication followed by tandem duplication after divergence from a common ancestor of <i>Dalbergioids</i> is the major cause of NLRome expansion. To the best of our knowledge, this is the first ever study to provide insight toward the evolution of <i>NLR</i> genes in this important tribe. In addition, accurate identification and characterization of <i>NLR</i> genes is a substantial contribution to the repertoire of resistances among members of the <i>Dalbergioids</i> species.
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