Corn Journal
  • Corn Journal
  • Author
  • Stalk Rot Booklet
  • Seed Testing
  • Corn Genetics
  • Pathology
  • Sponsors
  • Contact
"You can see a lot by just looking"-Yogi Berra

Corn genetic diversity

7/5/2016

 
One study of a single corn inbred (B73) indicated that it had 30,000 genes.  We benefit from a species with a huge genetic potential and a pollination system that encourages new mixes of genetics.  This has allowed the species to be used for food in a wide range of environments.  Some of those genes are turned on in response to the many microbes searching for the products of photosynthesis for their nutrition.  Microbes have genetics too! Some, like rust and smut fungi, survive by attacking living corn cells, drawing carbohydrates to the cell, and then moving on via spores before the host cells respond to the fungus.  Many fungal pathogens of corn simply kill a limited area of the leaf tissue, feed on the dead tissue, produce spores and infect new areas.  Corn varieties differ in how quickly and strongly they respond to the invasions.
 
One fungus that I find interesting is Bipolaris zeicola.  It was formally known as Helminthosporium carbonum.  There are genetic variants of this species that apparently feeds only on dead leaf tissue, often caused by insect damage or simply physical injury.  These variants apparently lack the genetics for either penetrating the live corn leaf tissue or overcoming the resistance system of most corn varieties.  At least one variant of this fungus produces a toxin that kills corn plant cells but most corn varieties have dominant gene that effectively blocks this toxin. However, very occasionally, a mutation of that dominant corn gene does occur while developing new inbreds.  If this mutation, now a recessive gene, becomes homozygous during the inbreeding process, the inbred is vulnerable to the toxin. The result is practically no defense to this variant (race 1) of B. zeicola.  The pathogen kills small leaf area of leaf, produces spores and spreads to new leaf tissue and eventually causes the whole corn plant to die early.  Because susceptibility is recessive, and the dominant toxin-resistant gene is present in most corn inbreds, this creates a problem for seed producers but not for hybrid growers.  Good that corn has genetic diversity.

Comments are closed.

    About Corn Journal

    The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.

    Archives

    December 2021
    November 2021
    October 2021
    September 2021
    August 2021
    July 2021
    June 2021
    May 2021
    April 2021
    March 2021
    February 2021
    January 2021
    December 2020
    November 2020
    October 2020
    September 2020
    August 2020
    July 2020
    June 2020
    May 2020
    April 2020
    March 2020
    February 2020
    January 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    January 2018
    December 2017
    November 2017
    October 2017
    September 2017
    August 2017
    July 2017
    June 2017
    May 2017
    April 2017
    March 2017
    February 2017
    January 2017
    December 2016
    November 2016
    October 2016
    September 2016
    August 2016
    July 2016
    June 2016
    May 2016
    April 2016
    March 2016
    February 2016
    January 2016
    December 2015

    Categories

    All

    RSS Feed

© COPYRIGHT 2023. ALL RIGHTS RESERVED
  • Corn Journal
  • Author
  • Stalk Rot Booklet
  • Seed Testing
  • Corn Genetics
  • Pathology
  • Sponsors
  • Contact