2 research outputs found
ACCase-inhibiting herbicides: mechanism of action, resistance evolution and stewardship
Herbicides play an important role in preventing crop yield losses due to both their weed interference ability and their capacity for increasing soil conservation in no-till systems. Group A herbicides or acetyl-CoA carboxylase (ACCase) are essential tools the selective management of glyphosate resistance in grass weed species. In this review, we describe important aspects of ACCase biology and herbicides targeting this enzyme, along with a discussion on stewardship programs to delay the evolution of herbicide resistance which can evolve either through target site and/or non-target site mechanisms. Sixteen-point mutations have been reported to confer resistance to ACCase inhibitors. Each mutation confers cross resistance to a different group of herbicides. Metabolic resistance can result in resistance to multiple herbicides with different mechanisms of action (MoA), and herbicide detoxification is often conferred by cytochrome P450 monooxigenases and glutathione-Stransferases. Regardless of whether resistance mechanisms are target or non-target site, using herbicides with the same MoA will result in resistance evolution. Therefore, while field surveys and resistance mechanism studies are crucial for designing reactive management strategies, integrated weed management plays a central role in both reactive and proactive mitigation of herbicide resistance evolution
Synthetic bacterial communities for plant growth promotion
PhD ThesisIncreasing food demands have driven the adoption of new global strategies to intensify
productivity without relying on heavy chemical treatments. In the last decades, plant-growth
promoting rhizobacteria (PGPR) have emerged as potential biofertilisers and biopesticides in
agriculture. The overall aim of this study was to research and develop approaches to
genetically engineer PGPR to improve their beneficial activities toward the plant partner.
A simplified PGPR community, a Bacillus consortium of three strains, was adopted to
study the complexity of the interactions occurring within the consortium and the plant
microbiome. Firstly, the comparative genomic analysis of the consortium highlighted the
unique and shared features responsible for plant promotion, microbial interaction and
cooperation among the strains (niche partitioning, organisation in biofilms with cooperative
mechanisms of quorum sensing, cell density control and antibiotic detoxification). Flux
balance analysis identified cross-feeding interactions among the strains and the metabolic
capability of the consortium to provide nitrogen to the plant, transforming it into forms
available for plant utilisation.
The consortium PGP potential was then investigated in vitro (LEAP mesocosm assay) and
in vivo (pot experiment) on the vegetable crop Brassica rapa. These tests show increased plant
growth when the strains were inoculated together rather than individually and when the
consortium was used as a supplement of the natural bulk soil microbiome. The in silico study
and the plant experiments highlighted areas for genetic improvement of the consortium
genomes.
Lastly, this work describes the development of a conjugation system that could be used
to efficiently engineer non-domesticated bacteria and bacterial communities, such as
rhizobacteria and plant microbiomes. The system, based on the plasmid pLS20, was developed
in Bacillus subtilis 168 and successfully tested on twenty-three wild type Bacillus strains and
three rhizobacillus communities.
The research presented here provides tools and approaches for the genetic
manipulation of rhizobacterial communities, with the ultimate aim of generating sustainable
agricultural bioformulations and sheds light on the complex interactions that can occur in a
model microbial PGPR consortia