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Unusual Symptomatology of Curly Top in Susceptible-Resistant Grafted Tomato Plants. D. E. Gardner, Graduate Assistant, Department of Botany, Utah State University, Logan 84321; O. S. Cannon, Professor, Department of Botany, Utah State University, Logan 84321. Phytopathology 62:187-190. Accepted for publication 31 August 1971. DOI: 10.1094/Phyto-62-187.

Grafted tomato plants comprised of Lycopersicon esculentum (curly top-susceptible) tops and L. peruvianum var. dentatum or L. peruvianum var. humifusum (curly top-resistant) lower stems and roots were inoculated with virulent isolates of curly top virus. Vein clearing, leaf contortion and curling, leaf stiffening, vein thickening, stunting, and phloem abnormalities of severity comparable to that in diseased nongrafted susceptible plants occurred in the scions. Yellowing typical of that in diseased-susceptible controls did not immediately accompany these symptoms in grafted plants, however, and photosynthetic tissue of these plants accumulated abnormally high chlorophyll concentrations. Longevity in grafted plant scions was greatly extended in comparison with that of controls. All of the diseased grafted plants eventually died, however. Inoculated reciprocal grafts (L. peruvianum var. dentatum scions and L. esculentum roots) exhibited the opposite reaction. The resistant scions developed yellowing, but this was not accompanied by other curly top symptoms typical of susceptible tomatoes. A separation of symptoms into at least two groups was therefore evident: those involving chlorophyll degeneration and those associated with internal and external morphological abnormalities (including vein clearing).