VIEW ARTICLE

Resistance

Temperature-Light Effects on Resistance of Poplar Cultivars to Races of Melampsora larici-populina. M. Chandrashekar, Graduate student, Department of Forestry, The Australian National University, Canberra, Australia 2600; W. A. Heather, reader, Department of Forestry, The Australian National University, Canberra, Australia 2600. Phytopathology 72:327-330. Accepted for publication 23 June 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-327.

The effects of contrasting temperatures (15 and 24 C) and light intensities (50 and 200 μE·m^–2·s^–1) during incubation on the relative resistance expressed by four cultivars of Populus spp. to three races of Melampsora larici-populina were assessed in a factorial experiment. Mean resistance of cultivars was highest and mean aggressiveness of races lowest under the high-temperature, high-light regime. Temperature, light, and their interaction also contributed the highest relative variances, although all main effects and most second- and third-order interactions were highly significant. These results suggest that environmental factors may be more important than genetic factors in regulating disease expression in this pathosystem. The fully and differentially interactive relationship of poplar cultivar, rust race, and environment could contribute to disease stability in this system.