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High pH-Ammonia Agar Immunodiffusion for Plant Viruses. Willem G. Langenberg, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, and Department of Plant Pathology, University of Nebraska, Lincoln 68503; Ellen M. Ball, Research Associate, Plant Science Research Division, ARS, USDA, and Department of Plant Pathology, University of Nebraska, Lincoln 68503. Phytopathology 62:1214-1217. Accepted for publication 2 May 1972. DOI: 10.1094/Phyto-62-1214.

A simple method for immunodiffusion of long flexuous viruses was developed. No chemical degradation or other treatment of the virus or plant juice was necessary, and existing antisera to undegraded viruses were used. Two long flexuous, two shorter rod-shaped, and three icosahedral plant viruses, or their components, formed precipitin lines in pH 9.1 agar plates containing free ammonia and detergent. Precipitin lines were visible as early as 6 hr after charging of the wells with virus and antiserum when the dishes were incubated at 37 C. Double-diffusion plates were prepared by pouring into tight-lid petri dishes 4 ml of a 1:1 mixture of 1% autoclaved agar and an unautoclaved solution of 0.2 M dibasic ammonium phosphate, 1% 1,3-propane diamine, and 0.2% Igepon T-73 (active ingredient 28-30% N-methyl-N-oleoyl taurate).