VIEW ARTICLE

Physiology and Biochemistry

Stimulation of Sexual Reproduction in the A² Mating Type of Phytophthora cinnamomi by a Substance in Avocado Roots. G. A. Zentmyer, Professor and plant pathologist, Department of Plant Pathology, University of California, Riverside 92521; Phytopathology 69:1129-1131. Accepted for publication 6 May 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1129.

Oospore formation was induced in unmated isolates of the A² mating type of Phytophthora cinnamomi by a substance in an extract or diffusate of avocado (Persea americana) roots. Thus, this heterothallic fungus functioned as a homothallic organism when provided with a specific organic (hormone-like) stimulus. The sexual stage also was initiated by the root extract in A² mating types of P. capsici and P. drechsleri, but not in A² types of several other Phytophthora spp. A¹ isolates of P. cinnamomi did not produce oospores in the avocado root extract. Similar stimulation was not found in extracts from roots of several other hosts of the pathogen. The stimulatory substance appears to be organic in nature, is nonvolatile, heat-stable, water-soluble, and can be extracted by several organic solvents.