The role of soil microbiota in the control of parasitic weeds

Parasitic weeds from the Orobanchaceae family, particularly Striga, Orobanche and Phelipanche spp., are responsible for substantial agricultural losses worldwide. A better understanding of the intricate chemical interaction between parasitic plants and their host crops, and the effect the rhizosphere microbiome may have on this, offers potential for developing sustainable and effective biocontrol strategies. We review the biology of parasitic plants, with a focus on host-derived signaling molecules such as strigolactones (SLs) and haustorium inducing factors (HIFs) that coordinate key stages of their lifecycle, and hence are potential targets for control through microorganisms. We highlight several examples of pathogenic microorganisms, and plant growth-promoting rhizobacteria (PGPR) and fungi (PGPF) that have been shown to suppress parasitic weeds. These microbes act through multiple mechanisms: direct antagonism of the parasite, enhancement of the host's defense responses, and interference with chemical signaling between host and parasite. Both laboratory and field studies are reviewed to evaluate the efficacy and future potential of these biological control agents.