Smut of wheat

About the disease of smut of wheat.

1. Smut of Wheat

2. Introduction belongs to Basidiomycetes order- ustilaginales Facultative parasites 1200 species mostly attacks the ovaries of grains only two kinds of spore- teliospores and basidiospores overwinter as teliospores on contaminated seed, plant debris or in the soil overwinter as mycelium inside infected seeds

3. Smut Rust Spore Intercalary Terminal Parasitism Facultative Obligate Heteroecism absent common spore number indefinite definite (4) mechanism of discharge passive active alternation of generation indistict distinct clamp connection common absent

4. Smut fungi Ustilago genus ( U. avenae, U. nuda, U. tritici ) Tilletia genus ( T. tritici, T. laevis, T. foetida, T. controversa, T. indica ). Sphacelotheca genus( S. sorghi, S. cruenta, S. reliana ) Urocystis Neovossia Entyloma etc.

5. Mode of infection Embryo infection - penetration usually takes place through the ovary wall. ex- Loose smut of wheat caused by Ustilago segetum . Seedling infection -dormant mycelium is remained in outer part of seeds when infected seed are sown and the myclelium become active and infect seedlings Shoot infection -pathogen directly enter through the young shoots (young buds). ex- Ustilago maydis (smut of maize)

6. Smut of wheat Smut fungi attack wheat plant and caused various type of smut disease. Loose smut- Ustilago segetum Flag smut- Urocystis tritici Hill bunt (Stinking smut)- Telletia caries, T. foetida Karnal Bunt- Neovossia indica

7. Loose smut of wheat Symptoms - distributed world wide symptoms can be only seen after the plants produce ears infected plants produce ears earlier than healthy ones in ears all spikelets and grain are smutted i.e. black powdery mass in place of grain the spores easily separated from host and are blown off by wind leaving a bare rachis behind thats why it is called as loose smut

8. Causal organism- Ustilago segetum var. tritici Pathogen is seed borne

9. Control Hot water treatment- seeds are soaked in water at 26-30 degree for 4-5 hours and quickly tranferred to hot water at 54 for 10 minutes. Luthra and Sattar's solar heat treatment- seeds are soaked in e]water for 4 hr in the forenoon of bright summer and followed by drying for 4hr in the sun use of fungicids- seed dressing with systemic fungicids such as carbovin (vitavax) and Benomyl use of resistant varities Biological control

10. Flag smut of wheat History- first found in Australia. In India, Butler was the first person to report . Symptoms - 1. pathogen attacks the stem and leaf. 2. symptoms can be seen at the time of maturation of crop. 3. grey or black linear sori appear on leaf blade and sheath. 4. leaf get twisted and begin to drop as flag 5. epidermis ruptured 6. if grain are formed they are shirvelled and do not germinate

11. https://bookstore.ksre.ksu.edu/pubs/MF3235.pdf

12. Causal organism- Urocystis tritici now known as U. agropyri Disease cycle - primary infection seed or soil borne Spore ball consists of 1-6 fertile cells and many peripheral cells spores at apex and produce infection thread after germination https://en.wikipedia.org/wiki/Urocystis_agropyri

13. Control Use of pesticides Cultural practices- early sowing, burnning of stubble, crop rotation Use of resistance varities Hot water treatment

14. Hill Bunt Or Stinking Smut or Covered Smut of Wheat Bunt possesses poisonous properties and flour of contaminated seeds is harmful for human consumption. Symtoms- 1. Infected plants are shorter than healthy ones in low smut and as of same height in high smut 2. Infected heads are slimmer and are usually bluish green and their glumes seem to spread apart and form a greater angle with the main axis 3.When mature kernels are broken, they are found to be full of a sooty, black, powdery mass of fungus spores that give off a distinctive odor resembling that of decaying fish because of Trimethylamine a volatile compound.

15. Low smut is caused by Tilletia caries (T. controversa ) High smut is caused by T. foetida

16. Karnal Smut of Wheat First reported by Mitra from Karnal (Haryana), India Symptoms- all the ears are not infected in a stool and in the ears all grains are not infected. smutted grains are irregularly distributed air borne or localized infection Causal organism- Neovossia indica First described by Mitra under the name of Tilletia indica which was later changed by Mundkur to N. indica.

17. (A) Head of wheat containing kernels infected with Karnal bunt. (B)Numerous wheat kernels infected with Karnal bunt (source- Plant pathology 5th edition by Agrios )

18. The Karnal bunt fungus overwinters as teliospores on the soil. In the presence of moisture, teliospores germinate by producing a basidium (promycelium) that, in turn, produces as many as 180 primary sporidia. The primary sporidia germinate and produce mycelia, which then produce large numbers of secondary sporidia. At the time of flowering, both primary and secondary sporidia are blown or splashed upward on wheat plants and those that reach the plant head infect the developing kernels The fungus is restricted to the pericarp of the kernel and there, as the kernels mature, the fungus produces large numbers of teliospores https://plantpathologyquarantine.org/pdf/PPQ_7_2_10.pdf