Disease Note

Segregation of Helminthosporium carbonum Race 1 Susceptibility in the Corn Synthetic BS13. D. R. Smith, J. G. Kinsey, and K. D. Kauffmann, DeKalb-Pfizer Genetics, DeKalb, IL 60115.  Plant Disease 69:1101, 1985.  Accepted for publication 3 September 1985.  Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-1101f.

Helminthosporium carbonum Ullstrup (= Cochliobolus carbonum Nelson) race 1 causes a severe leaf blight on corn (Zea mays L.) containing the hm allele for susceptibility.  During 1984, a newly developed proprietary corn inbred segregated for susceptibility to H. carbonum race 1.  This inbred originated from a cross of BS13 by an inbred known to be resistant to H. carbonum race 1.  Plants from BS13 cycle 1 and cycle 3 were tested against H. carbonum race 1.  Of 1,763 plants inoculated, 367 were susceptible.  The gene frequency of the allele conditioning susceptibility was calculated as 0.456.  BS13 was developed from Iowa Stiff Stalk Synthetic after eight cycles of recurrent selection.  Corn inbreds developed from these synthetics or from crosses involving these synthetics should be monitored for susceptibility to H. carbonum race 1.