Cyanobacterium Nostoc species mitigate soybean cyst nematode infection on soybean by shaping rhizosphere microbiota

Soybean cyst nematode (SCN, <i>Heterodera glycines</i> Ichinohe) is the most devastating and yield-limiting pathogen that threatens soybean production globally. Sustainable SCN disease management strategies are needed. In this study, a cyanobacterial strain was isolated from SCN-infected soybean soil and identified as <i>Nostoc punctiforme</i> using the cyanobacterial 16S rRNA gene sequence. When susceptible soybean plants were grown in the SCN-inoculated soil, <i>N. punctiforme</i> inoculants significantly reduced the total number of SCN eggs and second-stage juveniles (J2s), compared to the control with SCN inoculation only. Further microbial analysis showed that <i>N. punctiforme</i> inoculants changed the bacterial and fungal communities in the soybean rhizospheres and significantly increased the relative abundance of several bacterial and fungal species with potential nematicidal activities, suggesting the changes of soybean rhizosphere microbiota may partially contribute to the activity of <i>N. punctiforme</i> inoculants against SCN. However, <i>N. punctiforme</i> inoculants did not directly induce soybean defense reactions against SCN. Thus, <i>N. punctiforme</i> may be a potential microbial source against SCN invasion in soybean.