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Resistance

Resistance in Cucumis melo to Watermelon Mosaic Virus 2 Correlated with Reduced Virus Movement Within Leaves. Stewart M. Gray, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616, Present address: USDA/ARS, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; J. W. Moyer(2), and G. G. Kennedy(3). (2)Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616; (3)Department of Entomology, North Carolina State University, Raleigh 27695-7613. Phytopathology 78:1043-1047. Accepted for publication 26 February 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1043.

A resistance that involves suppression of the levels of watermelon mosaic virus 2 (WMV 2) was investigated in systemically infected muskmelon tissue. Differential temperature manipulation of WMV 2-infected whole plants increased the synchrony of systemic infection and facilitated studies on the kinetics of capsid protein accumulation in resistant and susceptible plants. Virus was extracted from 5-mm-diameter leaf disks collected from a single leaf at various times after virus replication began and quantified from immunoblots. Host tissue type did not affect extraction or quantification of the protein. Differential temperature treatment of susceptible plants increased the amount of capsid protein detected early in the infection but did not affect the maximum level accumulating in the leaves. Similar treatment of resistant tissue caused an increase in the intensity of the symptoms induced by WMV 2, but the symptom type, discrete chlorotic areas, was not changed. An increased level of capsid protein was associated with the increase in symptom severity in the resistant tissues. The resistance mechanism(s) does not affect vascular transport of the virus but appears to reduce cell-to-cell movement of the virus within leaves.