This Special Issue of Agronomy was dedicated to publishing original research or review papers dedicated to the study of the diversity of crop genetic resources and genetics of cultivated plant species relevant to agriculture worldwide. Plant genetic resources are the basic element of the genetic study of crops and allow for the genetic improvement of crops for agriculture. Likewise, the interactions of plants with their agrosystems, the relevance of the different cropping systems, the resistance of crops to biotic and abiotic stresses, and the interactions with the soil microbiota are relevant aspects, as well as the adaptation of the plants to different environmental conditions under the current climate changing conditions.