ARABIDOPSIS-THALIANA AS A MODEL FOR STUDYING SCLEROTINIA-SCLEROTIORUM PATHOGENESIS

Among the economically important plant pathogens, Sclerotinia sclerotiorum has an unusually broad host range attacking a wide range of crop plants. Pathogenesis of S. sclerotiorum is complex and not fully understood. Recent work in our laboratories has demonstrated the importance of oxalic acid (OA) in the infection process. S. sclerotiorum mutants specifically deficient in oxalic acid production are unable to infect host plants. We explored the possibility of using Arabidopsis thaliana as a model host due to its attractive genetic features. Here we show that Sclerotinia sclerotiorum readily infects A. thaliana. Moreover, OA mutants of S. sclerotiorum are non-pathogenic in A. thaliana. Thus, A. thaliana is not only a suitab e host for the fungus, but pathogenesis is likely to proceed in a manner similar to that described for its natural hosts. We have identified bacterial strains capable of degrading OA using a plate bioassay technique. Furthermore, using a plant bioassay, we show that these bacterial strains can prevent S. sclerotiorum infection in A. thaliana. These bacterial strains will serve as a source for isolating gene(s) for oxalic acid degradation. These genes may be useful in developing transgenic crop plants resistant to S. sclerotiorum infection. © 1992.