VIEW ARTICLE

Factors Affecting Manual Transmission, Purification, and Particle Lengths of Wheat Spindle Streak Mosaic Virus. J. T. Slykhuis, Research Scientist, Ottawa Research Station, Research Branch, Canada Department of Agriculture, Ottawa, Ontario, Present address: Department of Plant Pathology, Institute of Experimental Botany, Czechoslovak Academy of Sciences, Praha, Czechoslovakia; Z. Polák, Postdoctorate Fellow, National Research Council of Canada, Present address: Department of Plant Pathology, Institute of Experimental Botany, Czechoslovak Academy of Sciences, Praha, Czechoslovakia. Phytopathology 61:569-574. Accepted for publication 22 December 1970. DOI: 10.1094/Phyto-61-569.

Wheat spindle streak mosaic virus (WSSMV) was transmitted manually from diseased wheat plants collected in the field in early May or grown in infective soil in a growth room at 6-12 C. Juice from diseased plants had a low infectivity titer, and lost most infectivity within 1 hr at 10 C. Initial infectivity was not increased by various buffers or sodium sulphite solution with bentonite. Inoculum was still infectious after 1 hr if prepared by grinding diseased leaves in phosphate buffers at pH 9, 8, and 7 but not at lower pH levels. Virus in leaf pieces was inactivated by heating at 47.5 C for 10 min. Highest percentage infection was usually accomplished by preparing a wad of diseased leaves, then rubbing it on wet emery paper just before rubbing it on the leaves of each test plant. Particles observed in dip preparations from diseased wheat leaves were 12.8 × 190-1,975 nm, with peaks in numbers of particles of 275-300 and 600-625 nm. Preparations from differential centrifugation of juice extracted from infected wheat leaves in 0.5 m sodium borate at pH 9.0 and then emulsified with one-third volume of a 1:1 mixture of n-butanol and chloroform, and the final pellet resuspended in phosphate buffers, contained particles 90-1,000 nm long. Peaks in numbers of particles occurred at lengths ranging from 125-175 nm at pH 10 to 275-300 nm at pH 5. None of the preparations was infectious. The particles flocculated at pH 8.0 or lower. The results indicate that infectivity is associated with particles more than 1,000 nm long, but these are fragile, and hence break and lose infectivity quickly in expressed plant juice. It appears that no intact particles are retained through the procedure used to purify the virus.