black rust of wheat | stem rust of wheat | Botany Talk

                                                          From wikipedia

    Disease 

     Black rust of wheat or Stem rust of Wheat 

    Host 

    Primary Host - The primary host of  Stem rust of wheat or Black rust of wheat is Wheat (Triticum aestivum) 

    Alternate Host - The alternative host of  Stem rust of wheat or black rust of wheat is Species of the genus Berberis (barberry) and Mahonia.

    Causal Organism     

    Puccinia graminis f. sp. tritici

    CLASSIFICATION 
    Scientific classification of  Stem rust of wheat or Black rust of wheat

    Domain:

    Eukaryota

    Kingdom:

    Fungi

    Division:

    Basidiomycota

    Class:

    Pucciniomycetes

    Order:

    Pucciniales

    Family:

    Pucciniaceae

    Genus:

    Puccinia

    Species:

    P. graminis

    Distribution 

    Stem rust of wheat or Black rust of wheat is found throughout the world, but is more common in areas where conditions are favorable for the wheat pathogen. This is very problematic for wheat growers across the world.

    In the world - North America, Europe, Asia, Australia, Africa

    In India - Northern wheat-growing regions of India are occasionally seen in the central and southern parts of India

    Symptoms

    Symptoms on Wheat-

    1.  Presence of reddish-brown, elongated pustules (uredinia) on leaves and leaf sheaths.

    2. Leaves may start to yellow and die prematurely.

    3. As the disease progresses, the pustules become darker (black) due to the production of teliospores, hence the name "black rust".

    4. Infected tissues are brittle and break easily, leading to stagnation and significant yield losses.

    5. Severe infection causes grain shrinkage and reduced grain quality.

    Symptoms on Barberry- 

    1. Orange-yellow spots (spermagonia) appear on the upper surface of the leaves.

    12    2. Clusters of aecia form on the lower surface of the leaves, from which ascospores emerge which infect wheat.Life Cycle

    On Wheat - Uredinospores from infected wheat plants spread to new plants and cause repeated infections during the growing season.
    At the end of the growing season, teliospores form and overwinter in plant remains.
    In spring, teliospores germinate to produce basidiospores, which infect barberry plants.

    On Barbery - Basidiospores infect barberry, causing pycnidia (spermagonia) to form on the upper leaf surface. Aecia develops on the underside of the leaf, releasing ascospores.
    The ascospores infect wheat, completing the cycle.

    black rust of wheat | stem rust of wheat | Botany Talk
      From Schumann, G.L. and K.J. Leonard. 2000. Stem rust of wheat (black rust). The Plant Health Instructor. DOI: 10.1094/PHI-I-2000-0721-01


    Control Methods 

    1. Cultural methods of black rust of wheat control - 

    Crop Rotation -

    Farmers can replace wheat with non-host crops such as legumes (for example - soybeans and peas) or other grains that are not susceptible to stem rust. This reduces the accumulation of rust spores in the soil and on plant debris.

    Elimination of alternative hosts -

    This involves identifying and removing barberry plants from a certain area of ​​wheat fields. In some areas, barberry eradication programs have been implemented to manage stem rust at a regional level.

    Proper area sanitation - 

    Post-harvest practices such as tilling the bottom of wheat stalks and burning crop residues can help destroy overwintering teliospores. Proper composting of plant debris can also help reduce inoculum.

    2. Resistant Varieties of Wheat to Black Rust - 

    Resistant Varieties in India - HD2967, PBW343, NIAW 34 (Trimbak),HD 2851

    Resistant Varieties Worldwide - Veery Lines, Kavkaz, Gabo, Kenya Kasuku


    Chemical Control of Black Rust of Wheat - 

    Types of Fungicides 

    1. Protectant Fungicides:

      • Examples: Chlorothalonil, Mancozeb
      • Applications: Used before the onset of disease, usually in the early stages of crop growth.

    2. Systemic Fungicides:

      • Examples: Triazoles (e.g., Propiconazole, Tebuconazole), Strobilurins (e.g., Azoxystrobin), Carboxamides (e.g., Boscalid)
      • Applications: Used as palliative treatment during the early stages of infection. Often used in combination with protectant fungicides for a broad spectrum of control.

    3. Combination Products:

      • Examples: Mixtures of Triazoles and Strobilurins (e.g., Propiconazole + Azoxystrobin)
      • Applications: Typically used during critical growth stages, such as stem elongation and heading, when the crop is most susceptible to rust infection.

    Reference 

    1. Schumann, G.L. and K.J. Leonard. 2000. Stem rust of wheat (black rust). The Plant Health Instructor. DOI: 10.1094/PHI-I-2000-0721-01Read article
    4. Plant Pathology R.S.Mehrotra & Ashok Aggarwal edition 2nd

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