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Effects of Temperature and Soil Water Potential on Expression of Barley Stripe Incited by Helminthosporium gramineum. M. N. Prasad, Former Graduate Student, Department of Crop Science, North Carolina State University, Raleigh 27607. Present address of senior author: University of Alberta, Edmonton, Alberta, Canada; K. J. Leonard(2), and C. F. Murphy(3). (2)Plant Pathologist, Agricultural Research Service, United States Department of Agriculture, North Carolina State University, Raleigh 27607; (3)Associate Professor, Department of Crop Science, North Carolina State University, Raleigh 27607. Phytopathology 66:631-634. Accepted for publication 27 October 1975. DOI: 10.1094/Phyto-66-631.

Effects of day and night temperature on development of barley stripe were tested with artificially inoculated seedlings of barley cultivars Jefferson, Keowee, and N.C. 526, and with naturally infected seedlings of Tenn. 59-15. Jefferson, a resistant cultivar, showed no consistent pattern of temperature effects. With Keowee, greatest disease incidence (more than 50% infected plants) occurred at day temperatures of 6-22 C in combination with night temperatures of 22-30 C. N.C. 526 and Tenn. 59-15 developed greatest disease at 6-14 C day and 14-22 C night temperatures. Naturally infected seedlings of Tenn. 59-15 were grown in soil at three water potential levels. In two tests 15-16%, 64-84%, and 27-36% of the plants developed stripe symptoms in wet (1.0 bars), intermediate (7.1 bars), and dry (12.9 bars) soil, respectively. Carboxin (5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxanilide) seed treatment at 6 g/100 kg slightly reduced stripe incidence (39% in treated, 64% in untreated plants) in soil of intermediate water potnetial. In dry soil carboxin had no effect on stripe, and in wet soil carboxin at 6 g/100 kg caused stunting of plants and resulted in increased disease incidence (33% in treated, 15% in untreated plants).

Additional keywords: Hordeum vulgare.