The desert thorn apple (Solanales: Solanaceae: Datura discolor) is a commonly occuring annual plant in the deserts of North America and emerging model system for the study of co-evolution between plants and their natural enemies in arid environments. To facilitate future evolutionary genetics studies of this species, we assembled a crhomosome-scale genome assembly using long-read (PacBio HiFi) and Hi-C sequencing. We then identified the resistance gene repretoire of D. discolor and discovered an unexpected contraction of the Solanaceae-specific NRC-immune receptor network. Both NRC-helper genes and NRC-dependent sensor gene reporetiores were found to be contracted within this species and the Datura genus more broadly. This finding shows that certain sub-families of immune genes (particularly NRC5-8) are evolutionarily labile and suggest the need for additional work focused on the interplay between environmental factors and the evolutionary processes acting on the plant immune system.