Southern corn leaf blight and stalk rot (Bipolaris maydis, also known as Cochliobolus heterostrophus) infestation. Image Credit: Department of Plant Pathology , North Carolina State University, via Bugwood.org used under a Creative Commons Attribution-Noncommercial 3.0 License.

Cochliobolus heterostrophus strain PR1x412 is a MAT1-1, Tox1+, field isolate, and progeny of a cross of between strain PR1 collected by L. Hsu in Poza Rica, Mexico and strain 412. As described for C. heterostrophus strain C4, it is a race T, T-toxin producing strain. As described for strain C4, in 1970 race T of C. heterostrophus caused the worst epidemic in US agricultural history, destroying more than 15% of the maize crop. Subsequent research demonstrated that the epidemic was triggered by the unfortunate confluence of complex DNA recombination events in both the fungal pathogen and the plant host. Before 1970, C. heterostrophus was known as an endemic pathogen of minor economic importance, first described in 1925 by Drechsler; after the appearance of race T, this race was named “race O”. Note both fungal races are pathogenic to corn, but race T is highly and specifically virulent on Texas male sterile cytoplasm (Tcms) corn.

References:

• Drechsler, C. 1925. Leaf spot of maize caused by Ophiobolus heterostrophus, the ascigerous stage of a Helminthosporium exhibiting bipolar germination. J. Agric. Res. 31: 701-726.