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

Common smut of corn

12/21/2017

 
​Ustilago maydis, the cause of common smut of corn, has a complex life as it interacts with corn biology.  The dried galls in corn ears, tassels, or leaves include a powder composed of thousands of spores called teliospores.  These thick-walled spores, with a diploid nucleus are able to withstand many environments for many years on and in the soil.  When they germinate, on a corn plant, mitosis in the diploid nucleus creates short hyphal strands with haploid spores called basidiospores.  These spores germinate to produce short hyphal strands that fuse to form new hyphae with each cell containing the two haploid nuclei. These hyphae can form an appresorium on the leaf from which the fungus penetrates an epidermal cell.  This stage of the fungus is total biotrophic, receiving nutrition only from the living cells.
 
During the leaf stage of infection, the hyphae grow to surrounding cells, again invading and feeding on living cells.  As the nutrition is depleted, the two nuclei in the hyphae cells fuse to form a diploid and finally teliospores.
 
The fungus generally grows towards plant meristems.   These could be in those ear meristems located at each leaf node of the plant, resulting in the appearance of stalk smut galls but actually galls formed in those ear meristems that do not normally produce ears.
 
Infection is common in the silks of ears. Teliospores germinate, produce the haploid basidiospores, and short filaments on the silk.  These filaments fuse to form hyphae with the two haploid nuclei in each cell within the filament as they grow towards the ovule at the end of the silk.  Reaching the ovule, it invades to absorb the nutrients from the host cells, causing the cells to swell as it keeps the cells alive but absorbs the nutrients. It is during this time that the nuclei of U. maydis cells fuse to form diploids. Eventually these diploid cells develop the thick, walls of the teliospores, the tissue dries and teliospores spread in the wind.  These spores may remain dormant for several years until the next opportunity for infection of corn plants.
 
One of the functions of the abscission layer that develops at the attachment of the silk to the ovule after pollination is to stop intrusion of potential pathogens such as Ustilago maydis.  Consequently, infection of ears by this fungus is most frequent in poorly or delayed pollinated ear shoots.  Resistance to this disease includes good timing of pollen production and emergence of silks when the plant is under stress conditions.  Occurrence of the smut at the tips of ears suggests that poor pollination occurred at the end of the silking period.
 
Newly formed smut galls include both host plant material and fungus.  These fresh galls are relished as food in the Mexican culture.  Production of large quantities involves taking advantage of the host and pathogen biology, growing male sterile corn and spraying the silks with the teliospores saved from previous years. 
 


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