VIEW ARTICLE

Inhibition of Helminthosporium turcicum Spore Germination by Leaf Diffusates from Northern Leaf Blight-Susceptible or -Resistant Corn. M. E. Mace, Plant Pathologist, U.S. Department of Agriculture, Agricultural Research Service, Southern Region, National Cotton Pathology Research Laboratory, P.O. Drawer JF, College Station, Texas 77840; J. A. Veech, Plant Physiologist, U.S. Department of Agriculture, Agricultural Research Service, Southern Region, National Cotton Pathology Research Laboratory, P.O. Drawer JF, College Station, Texas 77840. Phytopathology 63:1393-1394. Accepted for publication 28 April 1973. DOI: 10.1094/Phyto-63-1393.

Diffusates collected from susceptible or chlorotic-lesion-type resistant corn leaves 1-3 days after inoculation with Helminthosporium turcicum, completely inhibited H. turcicum spore germination. The pH of diffusates from inoculated leaves ranged from 2.5-2.8. Diffusates from control leaves had pH values of 6.8-7.0. Percentages of spore germination in 3-day diffusates from inoculated and control leaves were similar when pH was adjusted over a range of 2.5-7.0. Percentages of germination were: 0 at pH 2.5; 3-7 at pH 3.0;46-56 at pH 3.5; and >95 at pH 4.5-7.0. Increased hydrogen ion concentration appears to account for the inhibition of spore germination in diffusates from inoculated leaves of both the susceptible and the resistant corn lines.