The invention is directed to recombinant antibodies which bind to Sclerotinia sclerotiorum antigens and comprise a single chain variable fragment (scFv). The antigen may be selected from SSPG1d or a portion thereof, aspartyl protease or a portion thereof, or whole Sclerotinia sclerotiorum mycelium. The invention also provides an antibody linked to an anti-fungal polypeptide. The invention extends to nucleic acid sequences encoding the antibodies, and expression vectors comprising the nucleic acid sequences. The invention is also directed to transgenic plants, seeds, tissues or cells transformed with the expression vectors. Methods for producing a transgenic plant that is resistant to Sclerotinia sclerotiorum, and for detecting Sclerotinia sclerotiorum in a biological sample utilizing an antibody which binds to Sclerotinia sclerotiorum antigen, and immunoassay kit for same are also provided.