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SOIL-BORNE WHEAT MOSAIC VIRUS HAS TWO GENOMIC RNA COMPONENTS, THE SMALLER OF WHICH UNDERGOES FREQUENT DELETION MUTATION
Abstract
Soil-borne wheat mosaic virus (SBWMV) has rod-shaped virions 20nm in diameter and lengths of 281 and 138nm, but in some isolates a 92nm particle is also present. Successive manual transfer of the latter isolate had given virus with 281 and 92nm long virions. This study concerns function and relationships of the three components. RNAs of 281, 138, and 92nm long virions (designated here by relative lengths as 1.0L, 0.5L, and 0.35L, respectively) were purified by three cycles of sucrose density gradient centrifugation. Infectivity assay with these RNAs proved the bipartite nature of SBWMV, the combination of 1.0L and either 0.5L or 0.35L RNAs being required for infection and for multiplication of progeny viruses. Infection of plants with 1.0L and 0.35L RNAs gave progeny of 1.0L and 0.35L only, but infection with 1.0L and 0.5L RNAs gave progeny with 1.0L and 0.5L, and also variants with various sizes smaller than 0.5L. Virions of 0.4L and 0.35L were functional in combination with 1.0L virion. Similarly, infection of plants by manual inoculation with 1.0L and 0.5L virions resulted in variants smaller than 0.5L. The ratio of the smaller variants to 0.5L virions increased with time. Variants smaller than 0.5L were found in wheat plants infected by the vector fungus, Polymyxa graminis, transplanted from the field in November and grown at 17(DEGREES) in a greenhouse until March, whereas virus from plants taken from the same field in March had 1.0L and 0.5L virions only. Regardless of the method of inoculation, the size profile of the variants varied from plant to plant. These results indicate that 0.5L RNA and SBWMV is unstable and produces deletion mutants when the host plants are grown at 17(DEGREES), with 0.35L RNA as the smallest functional molecule. The reason why 1.0L and 0.5L virions dominate the virion species infecting wheat plants in early spring is uncertain. The coat proteins of all isolates had Mr of 19,700. The Mr's of RNAs of 1.0L, 0.5L, 0.4L, and 0.35L virions, determined under denaturing conditions, were 2.28, 1.23, 0.97, and 0.86 x 10('6), respectively. A new virus group, furovirus (fungus-borne rod-shaped virus) is proposed for SBWMV.
Subject Area
Plant pathology
Recommended Citation
SHIRAKO, YUKIO, "SOIL-BORNE WHEAT MOSAIC VIRUS HAS TWO GENOMIC RNA COMPONENTS, THE SMALLER OF WHICH UNDERGOES FREQUENT DELETION MUTATION" (1982). ETD collection for University of Nebraska-Lincoln. AAI8306512.
https://digitalcommons.unl.edu/dissertations/AAI8306512