Volume 73 contains 4 reviews on contemporary and important topics in the agronomic sciences. In Chapter 1, "Interactions among Root-Inhabiting Fungi and Their Implications for Biological Control of Root Pathogens," fungi are defined, their distribution and abundance are discussed, and their role in agroecosystems is present. Chapter 2, "Dwarfing Genes in Plant Improvement," discusses advances in the role of dwarfing genes in plant improvement. Emphasis is placed on breeding and genetic aspects. Chapter 3, "A Review of the Effect of N Fertilizer Type on Gaseous Emissions," covers a topic that is of great environmental interest — the effect of nitrogen fertilizers on gaseous emissions. Chapter 4, "Rhizobia in the Field," is a comprehensive review of rhizobia including diversity, systematics, natural populations, and field introduction of rhizobia.