In general, organisms can inherit genes in two ways: vertical gene transfer and horizontal gene transfer.

The genes responsible for the symbiosis with plants, however, may be more closely related than the organisms themselves, acquired by horizontal transfer (via bacterial conjugation) rather than vertical gene transfer (from a common ancestor).

Horizontal and vertical gene transfer has occurred within and between fungal species of Cochliobolus and might be the reason for occurrence of highly virulent, toxin producing races of C. heterostrophus, C. carbonum and C. victoriae.