CONCENTRATION AND INFECTIVITY OF BARLEY STRIPE MOSAIC-VIRUS IN BARLEY

Barley stripe mosaic virus (BSMV) was extracted by grinding infected barley (Hordeum vulgare) leaves in 0.5 M sodium orthoborate, pH 9.0, and purified by differential and density-gradient centrifugation. The concentration of extractable virions in the youngest 2 leaves of infected plants grown at 13, 17, 21 and 25.degree. C was approximately the same for plants from the 2-leaf to the flag-leaf stage, suggesting that the infected plant has no long-lasting acquired immunity from the virus. In plants pretreated for 3 days at 25.degree. C, symptoms were more severe at a lower temperature than at a higher temperature, but this difference was not correlated with virion concentration. Polyacrylamide gel electrophoresis of BSMV RNA showed 2 RNA components for the Type strain, 3 for the ND18 strain, and 4 for the AM strain. Component I had the largest molecular weight RNA and component IV, the smallest. The ratio of component I to II in AM strain increased to about 1:1 when infected barley plants were maintained at 13.degree. C, but reverted to the normal 1:3 ratio when plants were returned to 25.degree. C. Component IV could not be recovered from flag leaves of plants infected with AM strain. No changes in proportion of components I to II or loss of any components were observed with plants infected with ND18 or Type strain kept at 13.degree. C until maturity.