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Postharvest Pathology and Mycotoxins

Sources of Inoculum and Infection Courts of Diplodia gossypina on Sweet Potato. Jing- Yi Lo, Graduate research assistant, Department of Plant Pathology & Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803-1720; C. A. Clark, professor, Department of Plant Pathology & Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803-1720. Phytopathology 78:1442-1446. Accepted for publication 15 June 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1442.

Diplodia gossypina was isolated from the 12-cm base of sweet potato sprouts growing from mother roots that were bedded adjacent to diseased roots, bedded in infested soil, or inoculated with a conidial suspension before bedding. On established vines that were wounded, D. gossypina was recovered 12 cm above and 24 cm below the point of inoculation 2 mo after inoculation. The fungus was not isolated from the proximal or distal ends of storage roots harvested from field plots in which vine cuttings or established vines were artificially inoculated or when vine cuttings were planted in artificially infested soil. Storage roots harvested from field plots with artificially infested soil had higher disease incidence than roots from noninfested plots. Roots harvested from inoculated vine cuttings or established vines did not differ from the uninoculated control in disease incidence. Freshly harvested storage roots inoculated by placing artificially infested soil on cut ends developed significantly higher disease incidence (16%) than the control (1%). Conidia of D. gossypina survived in field soil for at least 1 yr. Survival of the conidia in soil was reduced by high soil moisture. Thus, the pathogen may survive in soil and infect storage roots through wounds made at harvest causing postharvest decay.

Additional keywords: Java black rot.