Reciprocal interactions between the sorghum root microbiome and the parasitic weed Striga hermonthica

The soil microbiome plays a crucial role in protecting plants against various pests and pathogens. However, its impact on interactions between plants and parasitic weeds, such as Striga hermonthica, is poorly understood. In this study, sorghum plants susceptible to Striga were grown in 22 different field soils infested with parasite seeds. Significant variations in Striga infections were observed among the soils. When the most Striga-suppressive soil was gamma-irradiated, there was a significant increase in Striga attachments, highlighting the importance of the soil microbiome in disrupting parasite infection. In the presence of the soil microbiome, the Striga-susceptible sorghum plants performed similarly to three Striga-resistant genotypes. This effect was lost when the soil microbiome was eliminated by gamma-irradiation. Subsequent analysis revealed that Striga substantially affected the sorghum rhizosphere microbiome and that both the sorghum rhizosphere mycobiome and bacteriome composition significantly correlated with Striga attachment. Interestingly, certain fungal species in the sorghum rhizosphere mycobiome were only detected when Striga seeds were present. Further investigation showed that these fungal taxa originated from the Striga seeds and are known sorghum pathogens, suggesting a potential partnership between Striga and fungal pathogens to invade their shared host. Overall, our study demonstrated that the soil microbiome influences Striga infection and sorghum performance in a genotype-dependent manner, and the microbiome of Striga seeds affects the composition of the sorghum rhizosphere microbiome.