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Effect of Illuminance on the Resistance of Inbred Lines of Corn to Isolates of Colletotrichum graminicola. A. E. Jenns, Research associate, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616; K. J. Leonard, research plant pathologist, United States Department of Agriculture, Agricultural Research Service, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Phytopathology 75:281-286. Accepted for publication 18 October 1984. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1985. DOI: 10.1094/Phyto-75-281.

Three-week-old plants of six inbred lines of corn were inoculated in all combinations with four isolates of Colletotrichum graminicola. From 1 wk before to 1 wk after inoculation the plants were grown at day/night temperatures of 30/26 C and daytime illuminances of 455, 228, or 114 hlx. Lesion length, lesions per square centimeter, and sporulation per square centimeter decreased with increasing illuminance. Sporulation per lesion was highest at 228 hlx, slightly lower at 114 hlx, and lowest at 455 hlx. Isolate x line interaction effects were significant at P=0.11, P=0.10, and P= 0.07 for lesions per square centimeter, sporulation per lesion, and sporulation per square centimeter, respectively, when analyzed over all three illuminance treatments. When data for each illuminance level in each of the two trials were analyzed separately, the isolate x line interaction was significant at P <0.05 for one of six analyses for lesion length and sporulation per square centimeter. The levels of specific resistance present in the lines were estimated by three methods and the consistency of the estimates were compared. Estimates of specificity differed for different components of resistance.

Additional keywords: maize, quantitative disease resistance, Zea mays.