Rust and smut diseases of oats . content with classification, symptoms, pathogen, management .

2. SYSTEMATIC POSITION
KINGDOM Fungi
DIVISION Eumycota
SUB DIVISION Basidiomycota
CLASS Urediniomycetes
ORDER Uredinales
FAMILY Pucciniaceae
GENUS Puccinia
SPECIES Puccinia coronata var.avenae
RUST OF OATS
CROWN RUST- Puccina coronate var.avenae

3. FAVOURABLE CONDITIONS
• Crown rust develops best during mild to warm(20-25C) sunny days and mild
nights (15-20C) with adequate moisture for dew formation.

4. SYMPTOMS
• Uredinia form on both the upper and lower surface of infected leaves.
• In severe epidemics, leaf sheathes also become heavily infected.
• Uredinia are round to oval pustules, up to 5 mm long, and contain masses of orange-
yellow spores exposed by rupture of the leaf epidermis.
• After a week or two, the margins of uredinia may become black with formation of the
dark colored teliospores.
• Often telia form as secondary, black rings abound the orange-yellow uredinia.
• The leaf epidermis remains intact over the telia until after the leaves have died.

5. CROWN RUST OF OATS

6. PATHOGEN
• A mass of hyphae collects beneath the epidermis and, if early in
season, develops into an urediosorus.
• From the base of sorus numerous short, erect stalks arise and a single
urediospore is formed at end of each.
• Each uediospore is an oval, brown body, and consists of a single cell
with a thick wall provided with spines. The spore has usually 4 germ
pores arranged in an equatorial band.
• On germination the teliospore produces a 4-celled promycelium from
each of its 2 cells.
UREDIOSPORES
TELIOSPORES

7. LIFE CYCLE
• Oats crown rust is caused by a fungal pathogen Puccicina coronata var. avenae.
• The crown rust disease cycle starts with resting spores, teliospores germinating
early in spring to produce spores called basidiospores.
• These spores are carried by wind and they must infect an alternate plant, the
buckthorn (Rhamnus spp) , in order to complete the life cycle.
• It produces berries that birds feed on and then spread these seeds around.
• The basidospores infection on buckthorn results into production of aeciospores.
• The aeciospores are spread by wind and infect oats to cause crown rust.
• Spores that are produced on oats are called uredospores.
• These become secondary source of inoculum. Infections on oats later turn into
teliospores, the overwintering spores for the crown rust pathogen.
• The crown rust pathogen can also infect few wild grasses.

8. LIFE CYCLE

9. ECONOMIC IMPORTANCE
• Crown rust is the most widespread and damaging disease of oat.
• There have been severe epidemics in virtually every oat-growing region of world.
• Moderate to severe epidemics can reduce grain yield by 10 to 40%.
• Individual oat fields may suffer total crop failures.

10. MANAGEMENT
• Select cultivars with good resistance of leaf rust.
• Early sown oats have a higher risk of developing rust and other leaf diseases.
• Maintaining good soil nutrition and ensure that the crop is supplied with adequate
potassium.
• The fungicides for control of leaf rust on oats is Propiconazole, Tebuconazole,
Azoxystrobin+Cyproconazole.

11. SMUT OF OATS
Caused by Ustilago avenae
KINGDOM Fungi
DIVISION Eumycota
SUB DIVISION Basidiomycota
CLASS Ustilaginomycetes
ORDER Ustilaginales
FAMILY Ustilaginaceae
GENUS Ustilago
SPECIES Ustilago avenae
SYSTEMATIC CLASSIFICATION

12. SYMPTOMS
• The sori are formed in the spikelets.
• In early stages they are covered by a
thin, slivery membrane which ruotures
while the ear is emerging out of
sheath.
• The loose spore mass is shed or blown
away by wind leaving behind the bare
rachis.
• Early symptoms of the disease, before
flowering can be detected sometimes
by the discoloration of leaves.

13. PATHOGEN
• Sooty appearance of the mass brown powdery ustilospores
(ustospores, smut spores,chlamydospores, brand spores,
resting spores, pseudospores and teliospores) which
areformed in sorion any part of the host plant.
• Production of sessile basidiospores which are released
passively from the promycelium.
• The hyphae penetrate the pericarp and passes through the
parenchyma along the testa on the ventral side of the grain
and cross the basal endosperm to enter the scutellum.
• Mycelium mainy intercellular.
Ustilago avenae

14. ECONOMIC IMPORTANCE
• Loose Smut occurs annually in some fields and, while losses are not serious, the
numbers of diseased plants may increase rapidly, if infected seeds are used without
treatment for smut control.
• Under these conditions, yields may be reduced by 70-90%.
• Control measures include seed treatment.

15. MANAGEMENT
• This disease can be controlled only through the use of resistant
varities, hot water or solar energy treatment or systemic fungicide
treatment of the seed.