Deoxyradicinin and 3-epideoxyradicinol production by the sunflower pathogen Alternaria helianthi

The phytotoxic compound deoxyradicinin, a metabolite of Alternaria helianthi, was isolated from naturally infected leaves of sunflower (Helianthus annuus). The production of this toxin in liquid culture together with 3-epideoxyradicinol is discussed. Production of deoxyradicinin by liquid cultures was observed to decrease after successive sub-culture of the fungus on solid medium. All 10 accessions of Helianthus tested were sensitive to deoxyradicinin although some quantitative differences between lines were noted. Evidence is presented for the metabolism of deoxyradicinin by host leaf tissue.