This edited book aims to focus on microbial diversity in arid lands and deserts versus specific microbial assemblages associated with plants. The book explains ecological drivers that shape this diversity, how plant-associated microbiomes are selected, and their biotechnological potential are discussed. Diversity and functional redundancy of these associated PGPM make them very active in supporting plant improvement, health and resistance to drought, salt and other stresses, and these dimensions will be explored in this book. Implementing proper biotechnological applications of the arid and desert-adapted PGPM constitutes a sizeable challenge, and the book attempts to take up that challenge and help researchers in this field to gain a detailed understanding of PGPM from arid ecosystems. This book serves as a handbook for research workers, teachers, postgraduate students and extension personnel, other development workers, and policy planners engaged in arid zone development.