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Effects of Temperature and Illuminance on Resistance of Inbred Lines of Corn to Isolates of Bipolaris maydis. A. E. Jenns, Research associate, Department of Plant Pathology, North Carolina State University, Raleigh 27695; K. J. Leonard, plant pathologist, Agricultural Research Service, United States Department of Agriculture, North Carolina State University, Raleigh 27695. Phytopathology 75:274-280. 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-75-274.

Six inbred lines of corn were grown under three temperature regimes or three illuminance regimes for 1 wk before and after inoculation with Bipolaris maydis race O. Day/night temperatures were 30/26, 26/22, and 22/18 C with a daytime illuminance of 455 hlx (592 μmol m- 2 sec- 1 photosynthetic photon flux density). Illuminance regimes were 455, 228, and 114 hlx at 26/22 C day/night temperatures. The six lines were inoculated in all 24 possible combinations with four isolates of race O. Lesion length, infection efficiency, and sporulation per lesion were measured. In the analysis of spores per lesion, a significant interaction between isolates and lines was observed in plants grown at 114 hlx before and after inoculation but not in those grown at higher illuminances or for lesion length or infection efficiency under any environmental conditions. Lesion length and sporulation increased with increasing temperature and decreased with increasing illuminance. Infection efficiency was unaffected by temperature or illuminance. Lines differed in the extent to which their resistance was diminished by increased temperature or decreased illuminance, but there were no significant isolate x temperature or isolate x illuminance effects. The levels of specific resistance present in the lines were estimated by three methods and the consistency of the estimates was compared.

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