Host-induced silencing of a nematode chitin synthase gene decreases abundance of rhizosphere fungal community while enhancing

Abstract

Context A transgenic variety of soybean (Glycine max (L.) Merr.), H57, has been developed from wild-type variety Jack, with host-induced gene silencing of a chitin synthase gene (CHS) in soybean cyst nematode (SCN, Heterodera glycines Ichinohe), a devastating pathogen in soybean. H57 needs to be characterised for suitability to manage SCN, especially because rhizosphere microbial communities may be sensitive to genetically modified crops. Aims We aimed to evaluate the SCN resistance of H57 at the T7 generation, and analyse the impact on the rhizosphere microbial community of planting H57 into SCN-infected soil. Methods Infection with SCN was assessed at 60 days after planting of H57 and Jack into SCN-infected soil by examining recovered cysts from rhizosphere soil and comparing with an infected bulk soil control. For analysis of rhizosphere microbial communities (bacterial and fungal), 16S and ITS amplicons were identified by high-throughput sequencing, and bioinformatic analysis was used to define operational taxonomic units. Alpha diversity, using five indexes, and relative abundance were determined. Key results Soybean H57 showed significantly enhanced and heritable resistance to SCN compared with Jack. The diversity and richness (abundance) of the bacterial community of H57 and Jack were significantly and similarly increased relative to the bulk soil. The fungal community of H57 had considerably lower abundance than both other treatments, and lower diversity than the bulk soil. The relative abundance of only two bacterial phyla (Acidobacteria and Actinobacteria) and one fungal phylum (Glomeromycota), and three bacterial genera (Candidatus_Solibacter, Candidatus_Udaeobacter and Bryobacter) and one fungal genus (Aspergillus), differed significantly between rhizosphere soils of H57 and Jack. Conclusions Host-induced gene silencing of SCN-CHS substantially and heritably enhanced SCN resistance in soybean, did not significantly alter the rhizosphere bacterial community, but greatly suppressed the abundance of the rhizosphere fungal community, which was likely associated with boosted SCN resistance. Implications This study established a basis for interaction research between soybean with SCN-CHS host-induced gene silencing and the rhizosphere microbial community, and for potentially planting soybean H57 to manage SCN.