VIEW ARTICLE

Cytology and Histology

Ultrastructural Comparison of Peanut Infected with Stripe and Blotch Variants of Peanut Stripe Virus. N. A. Rechcigl, Former graduate research assistant, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061; S. A. Tolin, R. L. Grayson, and G. R. Hooper. Professors, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061. Phytopathology 79:156-161. Accepted for publication 10 August 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-156.

Two symptom variants of peanut stripe virus, stripe (PStV-S) and blotch (PStV-B), were compared ultrastructurally in the seventh quadrifoliolate leaf of systemically infected peanut (Arachis hypogaea 'Florigiant') sampled at five stages of expansion. The variants differed in the location of virus particles in cells and the severity of cytopathic effects, but not in particle length or type and location of cytoplasmic inclusions formed. Both variants of the virus are placed in potyvirus subdivision III. With either variant, cytoplasm in very young leaves was highly vesiculated, and pinwheel inclusions were located at the periphery of the cell, apparently attached to the plasmalemma near plasmodesmata. Scroll inclusions appeared in abundance in both PStV-B and -S infected cells at a later leaf expansion stage when symptoms were evident but indistinguishable as blotch or stripe. In more mature leaves expressing blotch or stripe symptoms, pinwheel and scroll inclusions were obvious in the cytoplasm and were often near mitochondria. Short, laminated aggregates were found infrequently. Virus particles were observed free in the cytoplasm, in linear arrays among membrane surfaces, and in monolayers sandwiched between membranes that extended as sheets through vacuoles. With PStV-B alone, particles were also observed in aggregates in the cytoplasm and along the arms of pinwheel inclusions. Membrane and organelle degradation was evident in cells infected with either variant, but was generally more severe with PStV-B. In fully developed leaves expressing distinctive symptom patterns, cells from light green areas contained numerous cytoplasmic inclusions and virus particles, whereas cells from dark green areas contained no observable cytoplasmic inclusions. Fewer virus particles were detected in extracts from dark green than light green areas and from PStV-S than from PStV-B tissue.