Rice Diseases PDF

PPA-312: Diseases of Field & Horticultural Crops & their Management - I Department of Plant Pathology, College of Agriculture, CSAUA&T, Kanpur  Rice diseases Prepared by: Dr. Manoj Kumar Chitara Rice blast  First report China in 1637 – Rice fever disease Japan in 1...

PPA-312: Diseases of Field & Horticultural Crops & their Management - I Department of Plant Pathology, College of Agriculture, CSAUA&T, Kanpur  Rice diseases Prepared by: Dr. Manoj Kumar Chitara Rice blast  First report China in 1637 – Rice fever disease Japan in 1704 – Imochi-byo Italy in 1928 – Brusone Economic losses Yield – 30-61 % or 70-80 % in severe cases M. grisea genome sequenced by Dean (2005) – First fungal pathogen (40 MB) and 9000 genes  Symptom The fungus attacks the crop at all stages from seedlings in the nursery to heading in the main field. Leaf blast: The lesions start as small ash- coloured, water-soaked bluish-green specks, soon enlarge and form spindle-shaped spots with a grey centre and dark brown margin. The spots join together as the disease progresses and large areas of the leaves dry up and wither. Similar spots are also formed on the sheath. Severely infected nurseries and fields show a burnt appearance.  Node blast: In infected nodes, irregular black areas that encircle the nodes can be noticed. The affected nodes may break up and all the plant parts above the infected nodes may die.  Neck blast: At the flower emergence, the fungus attacks the peduncle which is engirdled, and the lesion turns brownish- black, This stage of infection is as rotten neck/neck rot/neck blast/panicle blast, In early neck infection, grain filling does not occur and the panicle remains erect, In the late infection, partial grain filling occurs, Small brown to black spots also may be observed on the glumes of the heavily infected panicles. Yield losses are correlated significantly with the extent of the neck rot/blast  Etiology CaO: Pyricularia oryzae or P. grisea (anamorph) Magnaporthe grisea (telomorph/Sexual stage) Mycelium - hyaline to olivaceous, septate and highly branched, Conidia –pyriform to obclavate, Conidia are 3 hyaline to pale olive green, usually 3 celled, Ascospore - hyaline, fusiform, 4 celled and slightly curved,  Disease cycle Primary inoculum – Mycelium and conidia Secondary inoculum - Conidia Sporulating leaf bast lesion  Favorable condition Cloudy weather, More number of rainy days, Longer duration of dew Relative humidity – 93-99 % Low night temperature – 15-20°C or