Ricedisease(hjh)讲解.pptVIP

Rice disease Huang Jiang Hua 31 March, 2008 Rice diseases of economic importance that need careful attention for increased productivity in farmers fields are as follows Disease Causal organism 1. Rice blast* - Magnaporthe grisea 2. Rice sheath blight* - Rhizoctonia solani 3. Brown spot - Cochiobolus miyabeanus 4. False smut - Ustilaginoidia virens 5. Sheath rot - Sarocladium orysae稻帚枝霉 6. Root knot - Meloidagane spp. 7. Bacterial blight* - Xanthomonan campestris pv. oryzae 8. Bacterial leaf streak - Xanthominan campestris pv. oryzicola Rice blast Rice blast is one of the most important diseases of rice worldwide. It caused by a fungus that can attack the aerial parts of the rice plant at any stage of growth. Symptoms Rice blast is characterized by the appearance of lesions on the leaves, nodes, and panicles. On the leaves, lesions are typically spindle-shaped--wide in the center and pointed toward either end. Symptoms Large lesions usually develop a greyish center, with a brown margin on older lesions. Symptoms Under conducive conditions, lesions on the leaves of susceptible lines expand rapidly and tend to coalesce, leading to complete drying of infected leaves. Resistant plants may develop minute brown specks, indicative of a hypersensitive reaction. Symptoms Besides attacking the leaves, the fungus may also attack the stem at the nodes, causing neck rot, or at the panicle, causing panicle blast. Symptoms When a node is infected all parts above the infected node may die. When this occurs, yield losses may be large because few seeds in the panicle develop. Causal Organism Rice blast is caused by the fungus Magnaporthe grisea (anamorph Pyricularia grisea [=P. oryzae]).