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Diversity and invasion resistance relationships in rhizosphere microbial communities with consequences to soilborne disease suppression

Gupta Vadakattu: CSIRO

<div>Rhizosphere microbial communities can play an important role in the defence against plant pathogens and soilborne diseases. The presence of antagonistic microflora, spatial and temporal fluctuations in the soilborne pathogens, their antagonists and other rhizosphere microbes have consequences to disease impacts. In our work on biological suppression, in a targeted polyphasic approach, the functional and compositional attributes of bacterial and fungal communities, specific functional groups, catabolic diversity and interactions were explored in field and bioassay experiments. Suppressive soils generally exhibited greater community metabolic diversity, higher bacterial species richness and genetic diversity compared to that in non-suppressive soils. Exposure of soils to factors that promote disease suppression had greater influence on rhizosphere bacterial composition in suppressive soils. Also, multiple bacterial taxa with varying physiological and metabolic capabilities contributed to differences between suppressive and non-suppressive soils. As bacterial communities can respond rapidly to changes in seasonal conditions, greater diversity allows the plant select different members that contribute to similar functions. Suppressive fungal communities were characterized by higher diversity, higher connectedness, and more nodes indicating resilience to change. In highly connected biological networks, efficient resource exploitation by all species including niche overlap between pathogen and community can occur thus reducing opportunities for pathogen invasion, growth and disease incidence thereby improving temporal stability of disease suppression capacity. High genotypic richness and dissimilarity exert significant influence in determining the susceptibility of ecosystems for pathogen invasion.</div>