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 disease resistance (A)

8/23/2016

 
​Disease resistance in plants is not totally unlike that in humans.  A pathogen is detected, the host responds by producing hormones that ultimately result in production of pathogen-inhibiting chemicals that eventually stop the pathogen.
 
Corn leaf epidermal cells are tightly connected except for the stomata. The vast majority of microbes surrounding corn plants cannot penetrate the plants. The few that do have the capability, perhaps by enzymatically drilling through the epidermal cells to enter the leaf tissue, set off the alarm. In some cases, the plant’s first response is increasing the production of salicylic acid in the area of the invasion. This turns on the genes for production of the protein, often an enzyme, with the capacity of stopping the pathogen from spreading.  This final product may be effective against several potential pathogens or specific to one species.
 
Our company, Professional Seed Research Inc., offers a service of evaluating disease resistance in experimental corn hybrids for seed companies.  We culture the pathogens and then inoculate the plants to the fungal pathogens by applying a concentration of spores to the whorls of plants when at about V7.  It is common that this moist environment assures spore germination and infection in the leaf tissue that was in the whorl at the time.  We inoculate only one pathogen per plant to avoid the resistance mechanism triggered by another pathogen and therefore not representing the genetics of the hybrid.
 
A rain storm arrived the evening after we inoculated the nursery in 2016.  Symptoms for the southern corn leaf blight and northern corn leaf blight were very sparse on the respectively inoculated plants.  Instead there were common rust pustules in the areas of the leaves that should have shown the other two diseases.  The hypothesis is that the rust spores were distributed by the storm into the leaf whorls, and the rust fungus (Puccinia sorghi) infected the leaf tissue. This triggered a general resistance factor that inhibited the other two fungi (Bipolaris maydis and Exserohilum turcicum).  I recall this happening several years ago as well.  There is a published report of infection by either of the latter two fungi limiting the infection by the rust fungus.  Hopefully, in our case, inoculating much later with the intended pathogens will find that the general resistance factor will no longer be present.

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