VIEW ARTICLE

Etiology

Verticillium dahliae and Pratylenchus penetrans: Interactions in the Early Dying Complex of Potato in Ohio. M. J. Martin, Former graduate student, Department of Plant Pathology, The Ohio State University, Columbus 43210; R. M. Riedel(2), and R. C. Rowe(3). (2)Associate professor, Department of Plant Pathology, The Ohio State University, Columbus 43210; (3)Associate professor, Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 72:640-644. Accepted for publication 14 July 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-640.

In 1978, 1979, and 1980, field microplots in fumigated organic soil were used to evaluate the effects of Pratylenchus penetrans and Verticillium dahliae on growth and yield of potato. Data collected in 1980 established that potato early dying can be caused by a nematode-fungus interaction. All six combinations of low, medium, and high population densities of nematodes (~15, 50, and 150/100 cm³ soil) with low and high fungus inoculum densities (6.6 and 17.1 microsclerotia per 10 g dry soil) reduced plant top, root, and tuber weights 75, 60, and 36%, respectively, compared with plants grown in uninfested soil. Top and root weights were not reduced by low levels of either pathogen alone, but were reduced 40 and 36%, respectively, by the medium and high levels. Excepting a 12% reduction with the high nematode treatment, tuber weights were not reduced by any single pathogen treatment. In 1978 and 1979, initial populations of nematodes alone, ranging from 7 to 260/100 cm³ soil did not reduce tuber yield. In 1979, 75 and 260 nematodes per 100 cm³ soil reduced root weight ~25%. In 1979, all levels of fungus alone reduced top and root weight, but only high fungus inoculum density reduced tuber weight. Seasonal rainfall was 129 and 104 mm above average in 1979 and 1980, respectively, and 107 mm below average in 1978.