The Effect of Red-rich and Blue-rich Lighting on the Microbiome of a Tomato Crop Grown Under International Space Station Conditions of High Humidity and Elevated CO2

Customized lighting treatments are being investigated to optimize space crop production. The VEG-05 experiment on the International Space Station (ISS) presented here investigated the effect of red-rich and blue-rich lighting in Veggie on the microbiome of a dwarf tomato variety, Solanum lycopersicum cv. Red Robin. A plant and its associated microbiome drive plant growth promotion, as well as resistance to pathogens and environmental stressors. The microbiome was investigated using bacterial 16S rRNA gene and fungal ITS sequencing methods to identify bacterial and fungal communities on tomato fruit, leaves, roots, rooting substrate, and Veggie facility surfaces grown under red-rich or blue-rich lighting. The plants were also screened using culture-based methods for potential food-borne pathogens and plate counts for bacteria and fungi. Differences in microbial load were compared between lighting conditions, as well as between ISS and ground control treatments. Due to environmental stresses, fruit production was low on ISS grown plants, thus limiting the number of samples available for analyses from flight plants. This analysis determined the core microbiome and microbiological composition for tomato plants grown under a red-rich or blue-rich lighting treatment and microgravity conditions.
The core microbiome for flight plants included the genera Rhizobium, Azospirillum, Burkholderia, Dyadobacter, and Sphigomonas. However, Pseudomonas was the only genus common to all ground-control plants, due low diversity on leaf samples. Culture-based pathogen screening, corroborated by 16S rRNA gene and ITS sequencing, yielded negative results. This experiment provides valuable data on a fruiting crop grown on the ISS and how the plant microbiome may change due to different lighting conditions.