Link to home

Cannot retrieve the URL specified in the Content Link property. For more assistance, contact your site administrator.

Effects of dew-period temperature changes on initiation of infection in soybean by Phakopsora pachyrhizi.
M. R. BONDE (1), S. E. Nester (1), D. K. Berner (1). (1) USDA-ARS, Frederick, MD, U.S.A.

Our previous research suggested night-time and early morning dew-period temperatures in much of the U.S. are highly conducive for soybean rust. During these studies, dew-period temperatures were held constant. However, recognizing that dew-period temperatures are rarely, if ever, constant in nature, we decided to determine what effects temperature changes during the dew period might have on urediniospore germination and infection. Williams 82 plants were inoculated with isolate Alabama 04-1 at 2-3X10<sup>4</sup> urediniospores/ml 0.01% Tween 20, then incubated in dew 3 or 6 h at selected temperatures above the optimum (20°C) dew-period temperature for infection, or conversely 3 or 6 h below the optimum. Plants then were transferred to a 20°C dew chamber for the remainder of the 24-h dew period. Plants at 20°C the entire dew period served as controls. Water agar dishes seeded with urediniospores accompanied each plant. At the end of the dew periods, dishes were examined for germination and plants placed in the greenhouse. By 2 weeks, in each of four experiments, twice as many lesions had developed on plants that had begun the dew period at 29 or 32°C and then were transferred after 3 h to 20°C than on plants at 20°C the entire dew period. No or few urediniospores germinated at a constant 29 or 32°C. The study showed infection was more efficient with a declining dew-period temperature, and supported the original conclusion.<p><p>Keywords: Fungus, Legumes

View Presentation