VIEW ARTICLE

Ecology and Epidemiology

Subterranean Clover Red Leaf Virus Disease: Effects of Light Intensity on Plant Symptoms, Growth, and Virus Content. Katie Helms, Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, Canberra, A.C.T. 2601 Australia; W. J. Müller(2), and P. M. Waterhouse(3). (2)Division of Mathematics and Statistics, Commonwealth Scientific and Industrial Research Organization, Canberra, A.C.T. 2601 Australia; (3)Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, Canberra, A.C.T. 2601 Australia. Phytopathology 77:1297-1300. Accepted for publication 18 March 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1297.

Trifolium subterraneum (subterranean clover) inoculated with subterranean clover red leaf virus and control uninoculated plants were grown for 60 days at day/night temperatures of 25/20 C and with a 12-hr photoperiod of three light intensities: photon flux density 200, 400, and 600 ?mol m^–2 s^–1. High light intensity promoted the development of red leaves in infected plants, measured by the percentage of red leaves, as well as growth of infected and control plants, measured by leaf number and fresh weight. At all light intensities the fresh weights of tops and roots of infected plants were significantly less than those of control plants. At the highest light intensity the weight of tops of control plants was 66-fold greater than that of infected plants. More mortalities occurred at low light intensity than high and in infected plants than controls. Virus yield per plant, but not virus concentration in plant sap, measured by enzyme-linked immunosorbent assay was greater at the highest than those at the two lower light intensities. At all three light intensities the virus concentration in plant sap was about fivefold greater in tops than that in roots.