RUST AND SMUT OF OATS 48.pptx

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

1. 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

2. 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.

3. 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.

4. CROWN RUST OF OATS

5. 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

6. 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.

7. LIFE CYCLE

8. 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.

9. 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 .

10. 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

11. 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.

12. 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. The disease is internally seed borne and the mycelium can survive in its dormant state. Ustilago avenae

13. 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 .

14. 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.