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Etiology

Etiology of Planta Macho, a Viroid Disease of Tomato. J. Galindo A., Professor, Centro de Fitopatología, Colegio de Postgraduados, Chapingo, México; D. R. Smith(2), and T. O. Diener(3). (2)(3)Microbiologist and research plant pathologist, respectively, Plant Virology Laboratory, Plant Protection Institute, AR-SEA, U.S. Department of Agriculture, Beltsville, MD 20705. Phytopathology 72:49-54. Accepted for publication 30 April 1980. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982. DOI: 10.1094/Phyto-72-49.

A disease of tomato, locally known as “Planta Macho” (male plant) (PM) disease, occurs in the Mexican states of Morelos and Mexico. Symptoms resemble those induced in tomato by the potato spindle tuber viroid (PSTV), but are more severe; nucleic acid extracts from infected, but not from healthy, plants contained a low-molecular-weight RNA with electrophoretic mobility identical to that of PSTV; and infectivity distribution after electrophoresis in polyacrylamide gels coincides with the position in the gel of the disease-specific RNA. This RNA, therefore, is the etiological agent of the disease. The RNA might be a severe strain of PSTV, but preinoculation of plants with a mild strain of PSTV affords little, if any, protection against symptom expression of the PM agent. Also, several plant species that are susceptible to PSTV are resistant to the PM agent; and several others that are susceptible to both agents display symptoms when infected with PSTV but remain symptomless, when infected with the PM agent. We, therefore, consider the PM agent, not as a severe PSTV strain, but as a distinct viroid for which we propose the term Tomato Planta Macho Viroid (TPMV).