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Physiology and Biochemistry

Synthesis and Movement of Southern Bean Mosaic Virus in Cowpea Hosts with Virus-Induced Necrotic Local Lesions. C. W. Kuhn, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602; D. B. Adams, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602. Phytopathology 66:1298-1309. Accepted for publication 6 April 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1298.

Synthesis and movement of the cowpea strain of southern bean mosaic virus (SBMV-CS) were studied in three cowpea lines. At temperatures between 21 and 28 C, Early Ramshorn was systemically invaded without necrosis. Clay developed necrotic local lesions and no systemic symptoms, and plant introduction (P.I.) 399419 developed necrotic local lesions and systemic necrosis followed by death. No lesions developed at 32 C on Clay or P.I. 399419 and plant death in the latter host did not occur at this temperature. To prevent lesion formation, incubation of inoculated plants at 24 C could not be longer than 50-60 hours before transfer to 32 C. The length of the photoperiod after inoculation had little effect on number of lesions. Virus was synthesized readily, and to a similar degree, in Early Ramshorn and P.I. 399419 in both inoculated primary and systemically-infected trifoliolate leaves at both 24 and 32 C. In Clay, synthesis was slow but detectable in both inoculated and noninoculated leaves. Although more SBMV-CS was produced in Clay at 32 than at 24 C, the total nucleoprotein was less than 5% as much as in the other two hosts. Direct extraction and assay of RNA from host tissue indicated that there were not large quantities of free viral RNA in plants incubated at 32 C. Host necrosis caused by SBMV-CS did not inhibit virus synthesis or prevent virus movement to noninoculated portions of cowpea plants.

Additional keywords: hypersensitivity, virus localization.