Rice blast disease

Email: [email protected]
[email protected]

Taipei, Taiwan

1. Rice blast disease By: Jeevan Kumar Shrestha National Chung Hsing University [email protected] Academia Sinica, Taipei, Taiwan [email protected]

2. One of the most damaging diseases of rice This disease was first known as rice fever disease in China as early as 1637 Disease of rice blast first recorded in 1704,in Japan The causal organism was first detected by Cavara in 1891from Italy Reported from 85 rice-producing countries or regions worldwide Destroy rice that can feed 60 million people Introduction

3. Blast severely affects lowland rice in temperate and subtropical areas of Asia, and is highly destructive to upland rice in tropical areas of Asia, Latin America, and Africa (www.irri.org) Countries affected by rice blast (Wang et al., 2014)

4. Etiological agent Rice blast diseases is caused by Magnaporthe oryzae & Pyricularia oryzae . M. oryzae  is an ascomycete  fungus. Reproduce both sexually and asexually Survive in seeds, plant residues and weeds Optimum Relative Humidity. – 90% Optimum Temperatue – 20-25° C Toxin – Pyricularin & ά– Picolinic acid Spores of M. oryzae

5. Eleusine coracana (finger millet) Hordeum vulgare (barley) Leersia hexandra (southern cut grass) Lolium multiflorum (Italian ryegrass) Lolium perenne (perennial ryegrass) Oryza glaberrima (African rice) Oryza longistaminata (perennial wild rice) Oryza sativa (rice) Triticum aestivum (wheat) Hosts

6. Life cycle (Wilson & Talbot, 2009)

7. Symptoms occur in all above ground parts of the rice plant at all growth stages Infected roots have also been observed Seeds display brown spots after infection Symptoms

8. 1. Leaf Blast (seedling to tillering stage) Small to spindle‐shaped spots with brown border and gray center Dimension is 0.4-0.8mmx0.1-0.2mm Spots join resulting in drying and death of leaves 2. Collar blast (tillering stage) Entire leaf blade dries up when the base of the flag leaf is infected Types and symptoms of rice blast

9. 3. Panicle blast (booting to heading) Dark necrotic lesions that partially or completely cover the panicle base, or the uppermost internode , or lower panicle axis 4. Node blast ( tillering stage) Node of the stem turns blackish and breaks easily

10. Complete genetic resistance (vertical resistance) is conferred by major blast R genes named as Piricularia genes or Pi -genes. (Wang et al., 2014) Incomplete resistance (horizontal resistance) is often conditioned by more than one gene on different chromosomal regions. These genes referred to as quantitative resistant loci (QTLs) . (Wang et al., 2014) During interactions between rice and blast pathogens, products of the R gene can specifically recognize the corresponding elicitors of M. oryzae . All R genes have been mapped on all rice chromosomes except for chromosome 3 Host resistance

11. Host resistance is the most economical and environmentally friendly way of disease control. Physiological races and variation in pathogenecity of M. oryzae were first reported by Sasaki in Japan as early as 1922(Sasaki, 1992) Variation in pathogenicity of the blast fungus have been attributed : mutations, sexual hybridisation , parasexuality and heterokaryosis Rice cultivars containing only a single R gene to a specific pathogen race often become susceptible over time due to the emergence of new virulent races

12.  Rice blast is known to cause approximately 60% -100% yield losses ( Kihoro et al., 2013) Threatens food security ( Pennisi , 2010) Increase in the production cost and consumar price Environmental degradation due to the continuous use of pesticides Farmers are shifting into horticultural crops and livestock rearing Impact of rice blast

13. Presence of the blast spores in the air throughout the year Upland rice environment Cloudy skies, frequent rain and drizzles High nitrogen levels High relative humidity Low soil moisture High leaf wetness or dew period Favorable conditions

14. Disease resistance cultivar- IR 64, , Jin 23B, CO39, IR50, Pusa1602 and Pusa1603 Crop rotation Removal of crop residue from field Use healthy seed and planting materials Early sowing of seeds just after onset of rainy season Seed to a stand of 15 to 20 plants per square foot. Removal of weeds (ROUGING) Use balance fertilizers – no heavy use of N2 Disease management

15. Disease control Commonly used blasticides :   isoprothiolane , probenazole , pyroquilon , tricyclazole etc. Broad spectrum fungicide : azoxystrobin First spray - tillering stage Second spray – flowering stage Seed treatment – Tricyclazole or Beam 75 WP (4 gm/ kg seed) Biological control: Pseudomonas fluorescens  strain Pf1

16. International Rice Research Institute-Rice Knowledge Bank. IRRI: Crop Health, Disease: Rice Blast. http://www.knowledgebank.irri.org/ipm/rice-blast/symptoms.html Kihoro J, Bosco NJ, Murage H, Ateka E & Makihara D. Investigating the impact of rice blast disease on the livelihood of the local farmers in greater Mwea region of Kenya. SpringerPlus 2013, 2:308 Pennisi E. Armed and dangerous. Science. 2010;327:804–805. Pinoy Rice Knowledge Bank. Rice Blast. http://www.pinoyrkb.com Sasaki R. Extensive of strains in rice blast fungus. Journal of plant protection 1992; 634-644 Wang X, Lee S,Wang J, Ma J, Bianco T, Jia Y.Current Advances on Genetic Resistance to Blast Disease. Rice- Germplasm , Genetics and Improvement 2014; 195-208. Wilson RA, Talbot NJ. Under pressure: investigating the biology of plant infection by  Magnaporthe oryzae . Nat Rev Microbiol , 7 (2009), pp. 185-195 References