Soil Steaming Disturbance Alters Assembly of the Spermosphere Microbiome Leading to Differrent Rhizosphere Compositions

The spermosphere is the area around an imbibing seed where exudates drive microbial interactions. The developmental stage from seed to seedling is one of the most vulnerable to disease, however, few studies research the role of microbiome assembly. To prevent disease, soil steaming disinfestation can reduce the number of pathogens present. Therefore, understanding how assembly differs in steamed and non-steamed soil and the impact on plant health is vital for managing seedling diseases. To accomplish this, ITS and 16S amplicons were sequenced from soybean (Glycine max) epiphytes, steamed spermosphere, non-steamed spermosphere, steamed rhizosphere, and non-steamed rhizosphere using Illumina MiSeq. We hypothesize that more seed microbes will be transferred from seed to spermosphere in steamed versus non-steamed soil, which may translate into positive plant health outcomes. Plant biomass and seed pod yield were recorded to indicate plant health. Results demonstrate that the prokaryote composition of the steamed soil communities differed from that of non-steamed soil communities and soybean epiphytes. Moreover, the non-steamed soil was more stable in compositional variation across each sample. Plant biomass did not differ between treatments, but steaming had a significant effect on increasing yield (p=0.005). Future analyses will include comparing the transmission of taxa and functional genes from epiphytic communities to seedlings in steamed and non-steamed and comparing network properties. The spermosphere is a keystone growth stage for plants and by studying the assembly process of microbes from seed to seedling, we may be better able to manage seedling diseases.