The Conidia Application Device: Inoculation hardware to conduct plant pathology research in microgravity

Space-based plant pathology research must become common to support extraterrestrial crop production. Microbes, including phytopathogens, are inevitable in space-based bioregenerative life support systems. To support future space plant pathology research, we developed an inoculation system to apply fungal conidia (spores) of the powdery mildew phytopathogen, Golovinomyces cichoracearum (Gc) on to leaves of the host, Arabidopsis thaliana (At). Traditional ground-based inoculation protocols are not feasible in microgravity. Thus, the Conidia Application Device (CAD) was developed to aseptically transfer Gc conidia from a source container to plant canopies in custom-built petri dishes. The CAD system included a 3D-printed, cyclonic insert that interfaced with a vial of conidia and sealed completely within a 50-cc syringe. The syringe contained sterile air, which passed through the 3D-printed insert, aerosolized Gc conidia, and entered the dish through needleless Luer-lock connections. A secondary port on the Petri dish attached to a reservoir air bag to accommodate any excess volume of air injected into the dish. The ports on the Petri dishes were positioned to encourage airflow across the upper surfaces of plant canopies and promote inoculation. The CAD system was used to inoculate At canopies during ground-based pre-flight tests, resulting in successful Gc disease development.