Mutations

​Current news shows concerns that the Covid-19 virus is mutating. The strand of RNA coding for the protein affecting infection has a mutation in one of its 1300 nucleic acid codes, resulting in the substitution of the amino acid glycine for the amino acid aspartic acid. This substitution apparently increases the infectivity by the virus.
 
Mutations occur frequently in plants, animals, bacteria, fungi and viruses. The random slight change in a single nucleic acid in RNA or DNA generally is of no consequence and not noted. But these are the changes that allows for evolution of new species, including the development of Zea mays from a Teosinte species about 8000 years ago.  Mutations contribute to the adaptation of variation in pathogens to overcome resistance in their hosts.  Races of Exserohilum turcicum, the pathogen causing northern leaf blight, that overcomes single gene resistance in corn is such an example. We benefit from some mutations and we fight others.
 
Mutations not only occur in nuclear chromosome DNA but also in of cellular organelles such as mitochondria. Such a mutation in mitochondria DNA inhibited some corn varieties to not produce pollen.  Because mitochondria are carried into hybrids only from the female parent, hybrid seed production was made easier by reducing need for detasseling corn. Male fertility was overcome in growers field by using males with a mutation that overcame to mitochondria mutation and thus produced normal pollen in the hybrid.  Unfortunately, the pathogen fungus Bipolaris (Helminthosporium) maydis had mutants producing a toxin that destroyed these mutant mitochondria resulting in the race t of the pathogen destroying a large portion of the 1970 corn crop in the USA.
 
All aspects of life interact with natural occurrence of mutations.  Further discussions of corn mutations in Corn Journal can be found by searching mutations in this issue.