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This article in CS

  1. Vol. 22 No. 3, p. 623-625
    Received: June 26, 1981



Effects of Air Temperature on Disease Severity and Peroxidase Activity of Soybean Leaves Infected by Peronospora manshurica1

  1. J. M. Dunleavy2



The objectives of this study were to determine if soybean leaves infected by Peronospora manshurica, the downy mildew fungus, have a higher peroxidase activity than healthy leaves and to determine if peroxidase activity is releated to symptomatology. After leaves were inoculated with conidia, leaf chlorosis appeared in 8.5 and 4.2 days at 10 and 35 C, respectively. A high negative correlation (r=−0.98) occurred between air temperature and the appearance of chlorosis after inoculation. Disease symptoms were most severe at 25 C, but decreased at both higher and lower temperatures. Peroxidase activity of uninoculated leaves was affected only slightly by the air temperatures. Infection resulted in large, significant (p<0.01) increases in peroxidase activity at all temperatures. A highly significant correlation (r=0.97) occurred between leaf disease ratings at 10 days after inoculation and maximum peroxidase activity of infected leaves at 9 to 13 days after inoculation at the temperatures tested.

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