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Mechanical Transmission of Viruses from Sweet Potato. Rodrigo Alconero, Research Plant Pathologist, Federal Experiment Station, ARS, USDA, Mayaguez, Puerto Rico 00708; Phytopathology 63:377-380. Accepted for publication 25 September 1972. DOI: 10.1094/Phyto-63-377.

Distilled water was compared to 0.1 M concentrations of ascorbic acid, cysteine hydrochloride, sodium sulfite, thioglycolic acid, phosphate buffer, and diethyl-dithiocarbamic acid as additives to virus-infected leaf sap of sweet potatoes in mechanical inoculations. Week-old seedlings of Ipomoea batatas, I. nil, I. purpurea, and I. violacea became infected when their cotyledons were mechanically inoculated with leaf sap from sweet potato cultivar Sunny Side with feathery mottle symptoms, and P.I. No. 320448 with purple ring symptoms. No infection was detected when the first true leaves of sweet potato seedlings were inoculated. The use of distilled water as an additive resulted in appreciably greater percent infection over the other additives, except diethyl-dithiocarbamic acid. No consistent difference was detected in the symptoms observed in plants inoculated with either inoculum source or additive. The use of cysteine hydrochloride did not result in greater stability of the pathogen in infected sap. Pinwheel inclusions were observed in tissues of Sunny Side with feathery mottle symptoms, and long flexuous rods (average length, 750 nm) were observed in infected sap of cultivar P.I. No. 320448 and of the seedlings inoculated with both inoculum sources. Observations suggest similar infective pathogens and high variability of symptom expression due to cultivar differences.

Additional keywords: antioxidants, virus instability, host variability, host susceptibility, flexuous rod virus particles.