A hydroponic system for facilitating observation of plant virus infection in roots

Plant viruses usually spread from the infection site to upper young leaves through plant phloem along with the plant nutrient solution flow. To track the infection status of plant viruses in root systems, we established an independent and controllable hydroponic system for growing single N. benthamiana plants. The infection of tobacco mosaic virus (TMV-GFP) in roots of N. benthamiana grown in hydroponic system was evaluated. The results showed that the seed germination of N. benthamiana in hydroponic system on day 3 after sowing. By day 5, the hypocotyls had elongated and the cotyledons had expanded. By day 7, all seeds were germinated. Hydroponic seedlings showed cotyledon expansion at 3 d but slow leaf development, whereas soil-grown seedlings exhibited cotyledon expansion at 6 d with rapid leaf growth. Hydroponic plants were significantly taller than soil-grown plants at the same growth stage. After TMV-GFP infection, root growth of N. benthamiana was significantly inhibited, characterized by slowed lateral root development, thinner roots, and reduced root numbers. Both fluorescence intensity and viral accumulation of TMV-GFP in the roots of hydroponic plants increased significantly than those of plants in soil. In summary, this hydroponic system displayed several advantages for viral infection study in roots, such as non-destructive, real-time observation of roots and allows for single-factor control, effectively avoiding interference from soil cultivation. It might be a convenient technique for studying plant root-virus interactions.