Articles, Blog

The Life Cycle of Wheat Stem Rust

August 23, 2019

Destroying harvests for millennia the stem rust pathogen of wheat is a
sophisticated organism that continues to this day to threaten
the security of global wheat production. The emergence of the UG 99 group
of virulent stem rust races underscores the need to better
understand the mechanisms of resistance in wheat and to develop new varieties resistant
to current races stem rust. But the emergence and rapid spread of
new forms of virulence also prompts more fundamental questions.
How do new virulent races arise in the first place? and what factors contribute to the rapid
ongoing evolution this historic pathogen? Stem rust of wheat is named for the powdery
reddish-brown rusty color blisters or pustules that
develop on the stems and leaves of susceptible wheat lines grown under
conditions conducive to infection. This tale tale reddish-brown powder
found on infected wheat plants are spores of the fungus puccinia graminis the organism that causes stem rust. A single
pustule can produce tens of thousands of these spores called “Urediniospores” with each
one capable of infecting a wheat plant and producing yet
another pustule. Carried by the wind perhaps to a
neighboring plant, perhaps to another wheat field hundreds or even thousands of miles away
a microscopic urediniospore can land, germinate, and cause new
infection. Once inside the host tissue the pathogen extract nutrients from the
wheat plant cells grows and eventually produces a new
generation of urediniospores in such
abundance that plant’s tissue erupts, releasing the new spores into the
air to repeat the infection process
elsewhere. On and on the cycle goes. With roughly two
weeks from infection to sporulation this cycle of urediniospore multiplication can rapidly produce epidemic levels of
disease. A severe stem rust infection in the field is a dramatic and devastating sight but it is not the whole story. An
important point about the urideneospore cycle of infection is that it is a clonal method of spore production Random mutations, genetic copy errors, and potentially rare
cases of asexual hybridization aside, Urideneospores infect wheat tissue and produce exact copies of themselves.
For a highly virulent race of stem rust like ug99, it is this cyclical process of spore multiplication that causes
epidemic levels of disease within season and necessitates the development and
deployment of resistant wheat varieties. What a perfectly clonal cycle does not
explain fully is the emergence new virulent races for this it is instructive to shift our
attention away from the wheat host plant and to continue to follow the pathogen. As the growing season comes to an end
and wheat plants begin to set seed and die the stem rust pathogen does something
remarkable. Instead of producing more urediniospores it begins to produce black overwintering
spores called teliospores although teliospores cannot infect
wheat they are important for two reasons first they can survive in a dormant
state on dead wheat stubble something the more sensitive urediniospores cannot do and second it is in the teliospore
stage that the two haploid nuclei fuse together the first step toward
creating new genetic variation and possibly new virulence A period of cold temperatures is part of
the environmental requirement to break the dormancy of a teliospore at which point it can germinate and produce, through meiosis, haploid spores called basidiospores. Incredibly these basidiospores infect not wheat but certain species of the completely
unrelated woody perennial plant genus berberis or
barberry. Transported by the wind to barberry
plants near wheat fields basidiospores can germinate, infect, and create blisters called spermatogonia on the upper surface of barberry leaves. These blisters produce reproductive
cells called spermatia able to fertilize perceptive cells
called hyphae inside compatible neighboring spermagonia in this step of fertilization entirely novel genetic combinations
are achieved. Once fertilized the hyphae grow down through the barberry leaf
where they eventually produce stunning reddish pustules on the underside of
the leaf marked by numerous peach or orange colored tube-like structures called aecia when exposed to moisture these aecia,
quite visible to the naked eye, forcefully eject the next spore form of stem rust aeciospores. Carrying entirely new
combinations of genetic material due to the cycle of sexual recombination
on the alternate host barberry, these microscopic aeciospores can once again directly infect wheat
producing the brownish red urideneospores that are the
hallmark of this disease. The complex and amazing life cycle of
puccinia graminis suggests that achieving durable
resistance to wheat stem rust depends not only on the critical task of
developing more resistance is the primary host plant wheat but also on investigating the
prevalence and functionality of the alternate host
barberry, and utilizing knowledge of the complete
life cycle of the stem rust pathogen to limit the
emergence and survival of new virulent races.


  • Reply Jessi Jemi August 23, 2015 at 12:11 pm

    its sooooooo……useful to me …..fantastic video

  • Reply Wanjiru Kamau-Rutenberg September 9, 2015 at 1:37 pm

    wow! so accessible even to non-biologists!

  • Reply SHREEYANS PRATAP SINGH September 10, 2015 at 6:52 am

    thanks…very simplified

  • Reply Akash Inamdar October 12, 2015 at 8:18 pm


  • Reply Ashish kumar October 27, 2015 at 6:38 am

    nicely presented complex life cycle

  • Reply Rhythm Babbar December 6, 2015 at 3:42 pm

    So helpful…THANKS

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    thanks alot..really very helpful..great job.

  • Reply Yogesh Giri December 28, 2015 at 11:52 am


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    thanks a lot

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    Is that Marco Rubio Speaking

  • Reply Emily Conley February 28, 2016 at 10:35 pm

    Excellent video–thank you!

  • Reply Tomislav Dvorski February 29, 2016 at 8:32 pm

    thx, thx ,thx

  • Reply Lord Silver Esp April 4, 2016 at 9:35 am

    why has this video not been seen by scientists who are researching for rust prevention. it's so simple right let's find a way to make both plants more resistant to the cycle of ruddy rust.

  • Reply Fariha Fatima April 15, 2016 at 2:09 am

    its amazing video ……now my concept is clear about this complex life cycle……..thank u

  • Reply Heba Sayed May 12, 2016 at 11:35 am

    Fantastic .. Help me alot for my exam thanks alot โ™ก

  • Reply vijay shingala July 26, 2016 at 3:42 pm

    awesome video and narration. keep it up guys. it helped me a lot

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    Nice presentation

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    Thanks man i was trying for hour an hour to understand from book and u made me understood in less tha 10 minutes. thumb up to u

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    tnk u do much it was such a nice video… I understood it well

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    amazing video….thanks for uploading this.๐Ÿ˜Š๐Ÿ˜Š

  • Reply tabinda zaheen November 20, 2016 at 12:44 pm

    Very Nice video…plz direct me to the infection cycle of Fusarium oxysporum….plz its urgent…I have my exam

  • Reply summer dey February 3, 2017 at 8:59 pm

    ah this is so great thank you

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    super sir you have solved my dowt

  • Reply Kiran Timilsina February 18, 2017 at 6:32 pm

    Amazingly presented. Love to remake its Nepali version if given a chance for it!

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    Very technical info… Thanks;

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    awsm vdo

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    really helpfull video in botany

  • Reply Mida Ben April 25, 2017 at 5:44 am


  • Reply panagiotis zymaris May 2, 2017 at 10:27 am

    Holy shit this is a complex-ass fungus

  • Reply Madhuri rupert May 13, 2017 at 12:43 pm

    woah! this is so good explanation.thankyou sir

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    Wow it was really helpful thanks very much

  • Reply Leonie Vanpeteghem August 17, 2017 at 9:14 am

    Very clear! Thank you! Helped a lot with preparing my exam!

  • Reply soumya K. S September 22, 2017 at 2:24 pm


  • Reply Kunal Sonparote October 6, 2017 at 3:45 pm

    Thnx its really helpful

  • Reply Grace White October 19, 2017 at 4:39 pm

    Great video! Its very clear and informative. Wow, isn't nature so incredible? Even the parasites have such order and an amazing life cycle!

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    very helpful explanation

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    fantastic im gonna pass now!

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    Awesome man

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    AUA approves.

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    very nice explanation๐Ÿ‘

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    Thanks a lot clear concept about it….

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    reliable one

  • Reply Chhattar Singh April 1, 2018 at 12:45 pm


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    Amazing video

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    thank you so much for this vdo..

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    that's very helpful . thank you

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    Nicely done!! Amazing

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    thanks for the exccellent video

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    This video just solved my exam misery. Thank you so much. Explicitly explained.

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    Want more disese

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    It helps me so much. thank u

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    Tnxx for advice

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    Very nice presentation… ๐Ÿ‘๐Ÿ‘๐Ÿ‘

  • Reply Mohnish Maurya October 7, 2018 at 5:33 pm


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    Super ….

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    Amazing video

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    Very nice video

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    Excellent presentation.

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    Very useful๐Ÿ‘Œ๐Ÿ‘Œ๐Ÿ‘Œ

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    Best video sir

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    Very nice presentation add subtitles also…๐Ÿ‘

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    Good ๐Ÿ™‚

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    Thank you so much

  • Reply Asia Khan December 1, 2018 at 8:12 am

    Thank you soooooo much

  • Reply Kiran December 2, 2018 at 6:57 pm


  • Reply wahaj uddin December 5, 2018 at 5:22 pm

    I got goosebump watching your video. It remind me about the bengal famine that took place in india where 5 million people died starving due to crops failure caused by this disease.

  • Reply SHASHI KANT BHASKAR December 6, 2018 at 3:13 pm

    I love this video

  • Reply Dakshi Rawat December 24, 2018 at 2:41 pm

    Amazing explanation ๐Ÿ‘Œ๐Ÿป๐Ÿ‘Œ๐Ÿป

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    Sir hindi ma be video bana liya kro kabi

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    Very nice vedio

  • Reply Subhasree Dutta December 31, 2018 at 7:51 am

    Thank u so much

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    Nice information

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    Great Video๐Ÿ‘

  • Reply Jaffer 34m February 5, 2019 at 2:19 pm


  • Reply Sheena Shah February 12, 2019 at 4:21 pm

    Good work

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    Great video

  • Reply suraj patel February 25, 2019 at 3:01 pm

    amazing bro… that is very helpful and markable

  • Reply Sashi Shingh March 7, 2019 at 9:50 am

    this vedio is outstanding on puccinia soo amaz

  • Reply Sashi Shingh March 7, 2019 at 9:51 am

    very informative vedio. well declared

  • Reply Gagan Kini G March 19, 2019 at 2:27 am

    Excellent Explanation…pls make such videos on other types of diseases also…

  • Reply Pankaj Mapari April 10, 2019 at 4:05 pm

    u did it best๐Ÿ‘Œ

  • Reply Ahsan Haxi April 11, 2019 at 8:56 am

    amazing animation ! It solve all the confusions .

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    Such a helpful video

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    Greaaatttt…l love it

  • Reply Dhiru C S July 29, 2019 at 11:04 am

    Super video …am from kerala…Thanks a lot to solve the misunderstandings

  • Reply Sushmita Singh July 31, 2019 at 4:36 am

    brilliant! thank you for such lucid explanation

  • Reply Madhu Shukla August 7, 2019 at 6:34 pm

    Plzz make video on life cycle of agaricus

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