Plants naturally host complex microbial communities in which the plant and the
symbiotic partners act as an integrated metaorganism. These communities include
beneficial (i.e. plant growth promoting, PGP) microorganisms which provide
fundamental ecological services able to enhance host plant fitness and stress tolerance.
PGP microorganisms represent a potential bioresource for agricultural applications,
especially for desert farming under the harsh environmental conditions occurring in
hot/arid regions (i.e. drought and salinity). In this context, understanding the ecological
aspects of the associated microorganisms is crucial to take advantage of their ecological
Here, hot/desert ecosystems were selected and two contrasting plant categories were
used as models: (i) wild plants (i.e. speargrasses) growing in hot-desert sand dunes and
(ii) the main crop cultivated in desert ecosystems, the date palm. By using highthroughput
DNA sequencing and microscopy, the ecology and functionality of the
microbial communities associated with these plants were characterized. Additionally,
the PGP services of bacteria isolated from date palm were explored. I found that the harsh conditions of the desert strongly affect the selection and assembly of microbial communities associated with three different speargrass species,
determining a plant species-independent core microbiome always present among the
three plant species and carrying important PGP traits. On the contrary, in agroecosystems
where desert farming practices are used, the plant species, i.e. date palm
exerts a stronger selective pressure than the environmental and edaphic factors
favoring the recruitment of conserved microbial assemblages, independent of the
differences in the soil and environmental conditions among the studied oases. Such
selective pressure also favors the recruitment of conserved PGP microorganisms (i.e.
Pseudomonas sp. bacterial strains) able to protect their host from salinity stress through
the induction of root architectural changes regulated by the modification of the root
system auxin homeostasis.
Overall, we found that deserts are unique ecosystems that challenge the paradigm of
microbial community assembly, as it was defined from studies in non-arid ecosystems.
The understanding of the ecological features regulating the ecological properties of such
unique microbial community assembly will be a key-step to improve the chances of
successful application of ‘PGP microorganisms’ in arid agroecosystems.
|Date of Award||Jul 2018|
- Biological, Environmental Science and Engineering
|Supervisor||Daniele Daffonchio (Supervisor)|