Plant rhizosphere microbiomes are crucial for crops' health and productivity but the selection and specificity that govern crop microbiome assembly are not fully known. Herein, we examined bacterial communities of two cereals, durum (Triticum durum) and barley (Hordeum vulgare), and two legumes' species, chickpeas (Cicer arietinum) and bean (Faba been) under rainfed conditions and without fertilization practices. Our results demonstrate that microbiome composition and assembly are shaped predominantly by host species. Each species either cereals or legumes recruits a distinct rhizosphere microbiome, with the strongest host effect in Faba been. Moreover, crop microbiomes were dominated by a few dominant taxa belonging to Thaumarchaeota and Actinobacteria phyla, with Rhizobiales (Alphaproteobacteria) identified as the important biomarker taxa for both legumes. Our work provides comprehensive empirical evidence on host selection, potential sources, and enrichment processes for crop microbiome assembly, and has important implications for future crop management and manipulation of crop microbiome for sustainable agriculture.