Stinking Smut/ Common Bunt/ Hill Bunt of wheat

Disease of Wheat

1. COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po), Via Vaigai Dam, Theni-625 562 COMMON BUNT/ STINKING SMUT/ HILL BUNT OF WHEAT Student: Course Teacher: P. Deepa Gnana Sundari Dr. Parthasarathy .S 2015021026 Asst. Prof., Plant Pathology.

2. Common Bunt/ Stinking Bunt/ Hill Bunt Local Names Hill Bunt - Kotumai Malaikutti . Stinking Bunt - Kotumai Alukippothal . Other Names Covered Bunt - Kotumai Mutappattiruthal

3. Pathogen Tilletia tritici   (syn.  T. caries ) and  T. laevis   (syn.  T. foetida ), which are distributed throughout the world on spring-planted and autumn-planted wheat. T. controversa , occurs on autumn-planted wheat and also on numerous genera of winter annual grasses.

4. Distribution in World Asia Australia North and South America Europe

5. Distribution in India Haryana Punjab Himachal Pradesh Uttar Pradesh All the Wheat growing regions in India.

6. Historical Significance Stinking bunt is a disease that was recognized early in agricultural development because of its prominent symptoms and signs, e.g., black smelly masses of spores in the heads of wheat. M. Tillet , a French biologist experimented with the black spore masses in 1755. Even though this was prior to the time when the "germ theory of disease" was accepted, he did show that the spores were associated with the disease.

7. However, he believed that it was a "poisonous entity" associated with the black spore masses that actually caused the disease, not the fungus itself. It wasn't until nearly 100 years later that Anton de Bary , the Father of Plant Pathology, confirmed the parasitic nature of the smut fungus.

8. Economic Significance From the late 1800s until the 1930s, stinking smut was a devastating disease of wheat, particularly in winter wheat grown in the Pacific Northwest. Infection levels over 20% were common in Washington in the early 1900s, and between 25-50% of the Kansas wheat crop was lost to stinking smut in 1890.

9. Because of the dusty spore masses released during harvest, many "thresher" explosions occurred. Static electricity that developed around the combine machinery ignited the teliospore dust released by the combine. In 1915, 160 such explosions were reported in Washington.

10. One can visualize the panic that must have developed when a "thresher-combine" pulled by a 20-40 horse team caught fire in the middle of a wheat field from such a smut dust-induced explosion. Only when the organic mercury and several seed treatments became available after 1930 did losses from smut drop to much lower levels. Today, losses from smut rarely occur unless a grower chooses not to plant treated seed.

11. Pathogen and its characters Low Bunt - Tilletia caries ( (DC.) Tul . & Tul .) 1847) (syn.  Tilletia tritici   ( Bjerk .) ) High Bunt - Tilletia laevis   ( Kuhn.)           (syn.   Tilletia foetida  ( Wallr .) ) Dwarf Bunt - Tilletia contraversa   (Kuhn.) 1947)            (syn.   Tilletia calospora   (Pass.) )

12. Tilletia laevis   T. laevis  occurs in the wetter areas of the mid-west and eastern United States. Teliospores of  T. laevis  have reticulate,  globose  and smooth walled. No resting period. Germinate to produce primary  sporidia  which unite to form ‘H’ shaped structure. ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx

13. Tilletia caries Tilletia tritici  is found in the drier western areas of the United States. Teliospores of  T.tritici have have reticulate,  globose  and rough walled which gives them a “warty” appearance. . ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx.

14. Tilletia controversa Teliospores of T. controversa are yellow-brown to red-brown, globose , mostly 19-24 µm diameter, mature spores are typically surrounded by a hyaline gelatinous sheath 1.5-5.5 µm thick. In median view, the exospore is reticulate, with relatively large, regular, polygonal areolae , 1.5-3 µm high and 3.5 µm diameter.

15. https://www.google.co.in/search?q=dwarf+bunt+of+wheat+images&dcr=0&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjV6pXUx63aAhVIQ48KHcjXBh4Q_AUICigB#imgrc=WefTF8Em01uZjM:

16. Systematic Position – Tilletia caries Kingdom : Fungi Phylum : Basidiomycota Class : Exobasidiomycetes Subclass : Exobasidiomycetidae Order : Tilletiales Family : Tilletiaceae Genus : Tilletia Species : T. caries

17. Systematic Position – Tilletia foetida Kingdom : Fungi Phylum : Basidiomycota Class : Exobasidiomycetes Subclass : Exoxobasidiomycetidae Order : Tilletiales Family : Tilletiaceae Genus : Tilletia Species : T. foetida

18. Systematic Position – Tilletia controversa Kingdom : Fungi Phylum : Basidiomycota Class : Exobasidiomycetes Subclass : Exobasidiomycetidae Order : Tilletiales Family : Tilletiaceae Genus : Tilletia Species : T.  controversa

19. Life Cycle ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx.

20. These two smut fungi survive between growing seasons as teliospores on the surface of healthy seed or in the soil. They can remain viable in either location for a number of years, perhaps ten years or more, particularly if the spores remain dry on the seed surface.

21. When environmental conditions are favorable, each teliospore germinates, producing sporidia . After compatible sporidia form the H-shaped structure, the resulting dikaryotic , infectious hypha penetrates a seedling. As the plant grows, the fungal hyphae also grow, keeping pace with the apical meristerm .

22. H-shaped Sporidia . ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx.

23. Eventually, the hyphae replace the cells of the seed, and the individual cells of the smut fungus become teliospores . During harvest, the smut spores are released from infected heads as the heads pass through the combine used to harvest the grain. They contaminate other seed being harvested or are spread by the wind to the soil surface, later to be incorporated into the soil mass during cultivation.

24. Life cycle of Tilletia controversa ©https://www.google.co.in/search?q=dwarf+bunt+of+wheat+images&dcr=0&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjV6pXUx63aAhVIQ48KHcjXBh4Q_AUICigB#imgr

25. Mode of Spread Seed-borne - Spores can survive for 2 years. Soil-borne - Spores can survive for several years. Wind-borne When the conditions are favored, they germinate and cause infection.

26. Epidemology Cool temperatures (5-15°C/41-59°F) favor the germination of the teliospores . Usually the soil moisture, which favors seed germination, also favors spore germination. Sandy, humus rich soils favour infection. On the other hand, soils which are clayey and acidic are detrimental to infection. Potassium and phosphatic fertilizers increase the severity of infection.

27. Symptoms Wheat plants Infected wheat plants are slightly shorter than healthy plants. After heading, the spikelets of infected plants tend to "flare-out" and take on a greasy, off-green color. ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx

28. In cultivars that normally produce long awns (bristle-like structures), infected heads may have shorter awns, or even no awns . ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx

29. In place of normal seeds, infected kernels develop into "bunt balls”. ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx.

30. These are the remnants of what would normally be a seed, but in its place, the seed coat remains intact with the inside converted into a black mass of spores. ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx.

31. Wheat kernels The earliest evidence of infection occurs shortly after ovaries would normally be pollinated. Infected ovaries appear greasy with a dark green cast. When squeezed, such ovaries reveal a mass of black spores that smell like rotting fish. This odor is actually that of trimethylamine , which is produced by the smut fungus.

32. As the heads and kernels mature, the bunt balls develop into a hardened mass that looks like miniature footballs. The spores inside the mature bunt balls are released when the heads go through the combine harvester to produce the cloud of dust.

33. This dust also smells of rotting fish. Occasionally, both healthy seeds and bunt balls are found in the same head. ©https://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/StinkingSmut.aspx.

34. Symptoms – Dwarf Bunt Disease symptoms can be evident after early spring growth. Infected plants produce an abnormally high number of tillers. After heading, sori similar to those described for common bunt form instead of kernels. Sori of dwarf bunt are usually more rounded than those of common bunt, giving the spike a ragged appearance.

35. It is common for infection to occur in only a few spikes per plant and also in only a portion of the kernels of individual spikes. Usually kernels are completely transformed into teliospores , but partially diseased kernels can occur. This symptom can also occur in kernels infected with common bunt.

36. ©https://www.google.co.in/search?q=dwarf+bunt+of+wheat+images&dcr=0&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjV6pXUx63aAhVIQ48KHcjXBh4Q_AUICigB#imgrc=7OO3HIeH5uA7mM:

37. Integrated Disease Management Cultural control Use pathogen-free seed. Grow the crop during high temperature period. Adopt shallow sowing. Grow resistant varieties like Kalyan Sona , S 227, PV 18, HD 2021, HD 4513 and HD 4519.  

38. Chemical Method Treat the seeds with Carboxin ( Vitavox ) or Carbendazim ( Bavistin ) at 2g/kg. Captan , Manzate , Thiram , and Vitavax are registered but used alone give only fair control of seedborne common bunt. All are ineffective against soilborne common bunt. Triazole has been recommended against T.tritici at the rate of 19 µg/kg seed for seed-borne inoculum and 56 µg/kg seed for soil borne inoculum .

39. Difenoconazole seed treatment is recommended against dwarf bunt. Tilt (0.01%) is highly effective as seed treatment against the common bunt.

40. Biological Method Bacillus licheniformis , B. megaterium , B. pumilus and B. subtilis are reported as antagonists of the bunt pathogen in Australia. Pseudomonas fluorescens strain was reported to provide control of common bunt ( T. laevis ) by inhibition of teliospore germination.

41. Hokeberg et al., (1997) had reported that a strain of Pseudomonas isolated from roots and applied as seed treatment strongly and reliably suppressed common bunt ( T. caries ).