A robust hydroponic-based system for screening red clover (Trifolium pratense) for Fusarium avenaceum

Red clover (Trifolium pratense) is an important forage legume crop that suffers like most perennial crops from attacks by soil-borne pathogens. Fusarium root rot is one of the most serious diseases and at the same time problematic to identify resistance because of its hidden life in the soil. Current screening methods are laborious and hampered by limited reproducibility. To remedy this situation, we aimed to establish a simple and reliable hydroponics-based screening system to facilitate studies of red clover–Fusarium avenaceum interactions. First, the fungal spore concentrations were balanced toward the development of red clover plants grown hydroponically. We found that the optimum concentration was 30,000 spores in 2 L of hydroponic medium to ensure infection during the plant growth period in this system. The procedure was scaled-up to screen plants from 25 populations to identify red clover individuals with the improved resistance to F. avenaceum. Susceptible plants had approximately two-fold higher amounts of fungal DNA than resistant plants, demonstrating a correlation between the disease readings of the plants and pathogen DNA. We foresee this screening procedure meeting the needs of both applied breeding work and in-depth molecular studies of responses between this pathogen and its host plant. This method could be applied for the screening of other plant species for resistance to Fusarium spp. or to other root microbes.