Introduction

Abstract

Speaking before an assembly of the Deutsche Landwirtsehafts-Gesellschaft in 1904, Lorenz Hiltner, Soil Bacteriologist and Professor of Agronomy at the Technical College of Munich, emphasized the critical role of microbial activities in the “rhizosphere” in the nutrition and general health of plants. This initial use of the term was in reference to the zone of most intense bacterial activity around roots of the Leguminoseae. Hiltner stated, “The nutrition of plants in general certainly depends upon the composition of the soil flora in the rhizosphere.” He further surmised, “If plants have the tendency to attract useful bacteria by their root excretions, it would not be surprising if they would also attract uninvited guests which, like the useful organisms, adapt to specific root excretions.” Thus, Hiltner had already identified the two major influences of the rhizosphere on plants, and the topics which were to be most intensely researched during the next four decades. These topics are: (1) the relation of rhizosphere to plant nutrition, growth, and development, and (2) the influence of rhizosphere phenomena on pathogens and pathogenesis.