Rovira Rhizosphere Symposium - The Crawford Fund

Abstract
Th e rhizosphere represents a dynamic front or
region where plants meet and interact with
benefi cial and pathogenic microbes,
invertebrates, other plant roots and soil. Since
the identifi cation, in the early 1950s, of
involvement of root exudates in the plant–
microbe interaction a lot has become known
about the composition of the compounds and
the complex nature of the rhizodeposits
involved, their possible role in controlling
specifi c plant–biota interactions and soil, and
plant and environmental factors that aff ect the
process. However, our ability to specifi cally
manipulate these interactions for the benefi t of
plant health and growth is yet to successfully
and reliably reach the fi eld environment.
Examples of root exudate or rhizodeposition
induced changes in plant–microbe interactions
include (i) proliferation of specifi c genera or
groups of biota, (ii) induction of genes involved
in symbiosis and virulence, (iii) promoter
activity eff ects in biocontrol agents and (iv)
genes correlated with root adhesion. Th e
observation of plant variety-based diff erences in
root exudation/rhizodeposition and associated
changes in rhizosphere microbial diversity
suggests the possibility for the development of
varieties with specifi c root–microbe interactions
1 CSIRO Entomology, PMB No 2, Glen Osmond,
SA 5064, Australia
Email: Gupta.Vadakattu@csiro.au
2 Scottish Agricultural College, Edinburgh, EH9 3JG,
Scotland
How best can we design rhizosphere
plant–microbe interactions for the
benefi t of plant growth?
Vadakattu V.S.R. Gupta 1 and
Oliver G.G. Knox 2
The T Rovira R Rhizosphere R Symposium
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for improved fi eld performance. Th e eff ect of
foliar sprays of herbicides and nutrients on root
exudation and microbial communities opens
the possibility of managing rhizosphere
biological activity from above ground, that is a
‘designer rhizosphere’ to suit edaphic and
environmental variation. Although new
knowledge about the enormous diversity of the
soil microbial genome and the nature of
chemical language that can occur suggests a
vast complexity to the potential interactions,
recent developments in techniques provide hope
for the identifi cation of critical factors to help
manage this dynamic front for the benefi t of the
plant.
Introduction
Th e importance of plant–microbe interactions in
the rhizosphere region has been recognised and
appreciated for more than 50 years (Rovira 1956;
Lynch 1990; Drinkwater and Snapp 2007; Hawkes
et al. 2007). A number of reviews and books detail
the various aspects of the rhizosphere from both
the plant and microbial perspective (Bowen and
Rovira 1999; Singh et al. 2004; Watt et al. 2006;
Cardon and Whitbeck 2007). We now know a
lot about the spatial and temporal dynamics of
diff erent microbial groups in the rhizosphere and
have some knowledge of the factors that infl uence
the populations and activities of soil biota in the
rhizosphere.
Th rough rhizodeposition plants can aff ect
rhizosphere microbial diversity and activity and
resistance to pests and diseases; support benefi -