VIEW ARTICLE

Ecology and Epidemiology

Subterranean Clover Red Leaf Virus Disease: Effects of Temperature 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; P. M. Waterhouse(2), and W. J. Müller(3). (2)Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, Canberra, A.C.T. 2601 Australia; (3)Division of Mathematics and Statistics, Commonwealth Scientific and Industrial Research Organization, Canberra, A.C.T. 2601 Australia. Phytopathology 75:337-341. Accepted for publication 30 August 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-337.

Subterranean clover (Trifolium subterraneum) plants inoculated with subterranean clover red leaf virus and uninoculated control plants were grown under natural light at five different day/night temperature regimes. Development of red pigment and time for development of red pigment were a function of temperature. At 20/15, 25/20, and 30/25 C older leaves of inoculated plants developed bright red pigment, whereas at 15/10 and 33/28 C they developed mottled reddish-brown or brown pigment. These red-pigmented leaves developed earlier at 20/15, 25/20, and 30/25 C than at 15/10 or 33/28 C. The maximum percentage of red leaves was higher (80%) at 20/15 and 25/20 C than at other temperatures. At harvest (60 days after inoculation), numbers of leaves per plant and fresh weights of both tops and roots of inoculated plants were lower than those of control plants at all temperatures. The temperature response pattern in relation to number of leaves per plant and fresh weight differed for inoculated and control plants. For inoculated plants, the maximum number of leaves per plant and fresh weight of both tops and roots was at 33/28 C. For control plants, the maximum number of leaves per plant and fresh weight of both tops and roots was at 20/15 and 25/20 C. The temperature response pattern for relative virus concentration as measured by enzyme-linked immunosorbent assay (ELISA) was inversely related to fresh weight. At 15/10, 20/15, and 25/20 C, relative virus concentrations were greater than that at 30/25 C and this in turn was greater than that at 33/28 C. The assessed yield of virus was approximately 400 to 700 ng/g fresh weight for plants grown at 15/10, 20/15, and 25/20 C.