Ustilago maydis Virulence Assays in Maize

The basidiomycetous smut fungus Ustilago maydis (U. maydis) infects all aerial parts of its host plant maize (Zea mays L.). Infection symptoms are seen in the form of prominent tumors on all aerial parts of maize, after the establishment of a biotrophic interaction with the host usually around 5-6 days post infection (dpi). The fungus colonizes the various developmentally distinct aerial organs at different stages of development to form these prominent symptoms. Although being a biotrophic plant pathogen, U. maydis can easily be cultivated under axenic conditions to produce a standardized inoculum. The infections can be carried out under laboratory conditions by syringe inoculation on all the aerial organs of maize. This protocol has been successfully utilized to infect all the aerial organs of maize and formulate the virulence assays in U. maydis making it an excellent model system to study phyto-pathological investigations (Schilling et al., 2014; Redkar et al., 2015).