VIEW ARTICLE

Physiology and Biochemistry

Effects of Verticillium dahliae on Gas Exchange of Potato. R. L. Bowden, Former graduate student, Department of Plant Pathology, University of Wisconsin, Madison 53706, Current address: Department of Plant Pathology, Kansas State University, Manhattan 66506; D. I. Rouse, Associate professor, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 81:293-301. Accepted for publication 29 October 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-293.

Growth-chamber and field experiments were conducted to determine the effects of Verticillium dahliae on gas exchange of potato. Infection caused lower stomatal conductance, lower transpiration, and higher leaf temperature in leaves of all ages. Infection reduced carbon assimilation rate in high light, but reductions were not always observed in low light. Infection did not affect dark respiration. Intercellular CO₂ concentration was decreased and leaf water use efficiency was increased in diseased nonsymptomatic leaves. However, diseased chlorotic leaves often did not show this effect. The rate of stomatal opening in the morning was slower for diseased leaves compared with nondiseased leaves. Infection did not affect the relationship between assimilation rate and stomatal conductance in high light. Changes in gas exchange caused by infection with V. dahliae matched previously reported effects of drought on potato gas exchange.