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

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

10. 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

11. 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

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

13. 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/Uro
cystis_agropyri

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

15. 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.

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

18. 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.

19. (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 )

20. • 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