Pathogen mutations

​Corn’s past and its future is driven by mutations, allowing for humans to select desirable characteristics.  Because most meaningful mutations generational result in changes is recessive genes that only become expressed when, in diploids, homozygous for that recessive gene, the mutations may not become evident in hybrids but only after inbreeding.
 
Bacteria and fungi also have mutations but most of their life cycle is controlled by haploid versions of DNA.  Consequently, a mutation can have immediate effect on a potential pathogen.  Most of these organisms have high rates of reproduction and spread.  Mutations in a potential pathogen resulting in a new protein that allows blocking the detection of a pathogen by the host plant can result in success of the pathogen to further invade the plant.  Races of Exserohilum turcicum have specific mutations that block the turning on of specific lesion size restriction in corn of Ht1, Ht2, Ht3 and Ht4.  Clavibacter michiganensis is a bacterium species with multiple subspecies that are essentially mutants adapted to specific hosts including wheat and tomatoes.  A mutant was identified on corn in Nebraska in 1970 as the cause of Goss’s wilt of corn.  
 
Mutations in potential pathogens will continue, as will mutations in corn.  Diversity is good, most of the time, and necessary for all of us into the future.