Chapter 7 Exploring the Ecological Significance of Microbial Diversity and Networking in the Rice Ecosystem Radha Prasanna, Lata Nain, Alok Kumar Pandey, and Saswati Nayak 7.1 Introduction Rice is the world’s most important food crop in terms of ensuring global food security and the livelihood of millions of producers. Broadly speaking, rice is grown in more than 100 countries, with a total harvested area of about 153 million ha, and production of more than 600 million tons annually. Yields range from less than 1 t ha –1 under very poor rainfed conditions to 10 t ha À1 in intensive temperate irrigated conditions (Zeigler and Barclay 2008). The consumption of rice exceeds 100 kg per capita annually in many Asian countries, providing 20% of the direct human calorie intake. Asia accounts for over 90% of the world’s production of rice, where the poorest of the poor spend up to 50% of their total income on rice alone. Rice is grown in a wide range of ecological environments (from dryland to flooded land, even under water layers several meters deep, and at varying altitudes (from sea level to 3,000 m above sea level), diverse climates (from tropical to temperate) and different soil types (from saline soils along sea coast to upland soil with toxic aluminium levels). In general, rice cultivation systems are classified as irrigated, rainfed lowland, upland and others. About 50% of the area under rice comprises intensive irrigated systems, which account for 75% of global rice production and represent the home of the Green Revolution in rice. The rice ecosystems constitute artificial biotopes of a dynamic character. They represent one of the most extensive freshwater ecosystems on Earth, while as “wetlands” they are characterized by unique biogeochemical cycles and variable microbial communities. The biocenoses in them are formed by the association of two micro-organizations – that of water and that of soil, which partly overlap. R. Prasanna (*), L. Nain, and A.K. Pandey Division of Microbiology, Indian Agricultural Research Institute, New Delhi 110012, India e-mail: radhapr@gmail.com S. Nayak National Institute of Science, Technology and Developmental Studies, New Delhi 110012, India P. Dion (ed.), Soil Biology and Agriculture in the Tropics, Soil Biology 21, DOI 10.1007/978-3-642-05076-3_7, # Springer-Verlag Berlin Heidelberg 2010 139