Physiology of tobacco etch virus-induced wilt of Tabasco peppers

Abstract

A change in permeability, indicated by a release of sodium and potassium ions, was detected in the roots of tobacco etch virus (TEV)-infected Tabasco pepper plants 24–48 hours before wilt symptoms occurred. The permeability change also preceded a decrease in the respiratory rate by 12–24 hours, and histological changes by 24–48 hours. None of these changes occurred in roots of noninoculated control plants, in roots of TEV-infectedpepper varieties which do not wilt, or in roots of Tabasco pepper infected with viruses which do not cause wilt. Since the change in permeability appeared to be specific for roots of TEV-infected Tabasco pepper, and since this preceded any other observable symptoms, a causal relationship between permeability change and wilting is suggested. No permeability changes were observed in systemically infected Tabasco pepper leaves. In root extracts of TEV-infected Tabasco pepper plants at the first day of wilt, a decrease in ascorbic acid content, an elevated enzymatic oxidation of ascorbic acid, a pronounced accumulation of polyphenols, and an increase in peroxidase activity were detected, but polyphenol oxidase activity was unchanged. Wilted plants recovered when their root tips were excised and the roots placed in water. This indicates that wilt results from the failure of water to reach the xylem rather than from blockage of water transport in the xylem itself.