Wheat blast disease – the new enemy knocking at our doors?

India is now the second largest producer of wheat in the world with about 12-13% share in total world wheat production! Production level of wheat in India has had a quantum jump from 6.46 million tons from an area of 9.75 million hectares in 1950-51 to about 93 million tons from an area of about 30 million hectares today. This was possible due to the green revolution,ushered during mid-sixties by our scientists and farmers in developing new wheat varieties/cultivars that gave higher yield and were disease resistant and drought tolerant. Most of the wheat produced in India is consumed domestically and any adverse effect on wheat production will not only impact the livelihood of millions of wheat farmers but also have a devastating effect on national food security.

Although the total production and productivity has increased over the years, wheat production has always faced challenges arising from un seasonal rains, droughts, pests, diseases, hailstorms etc. Central and state government policies, initiatives and timely interventions with the support from our farmers has helped us over come such challenges. However, due to back to back droughts for last two years, we are likely to see a wheat import this year!!

In addition to these prevailing challenges, a new enemy is knocking at our doors today! Wheat blast disease, which was restricted to southern America, has recently made its appearance in South Asia, Bangladesh! Wheat blast disease is a deadly and a baffling foe. Regarded as most fearsome and intractable, it is caused by a fungus Magnaporthe oryzae. There is a severe outbreak of this disease in key wheat districts of southwestern Bangladesh affecting nearly 15,000 hectares of wheat production (http://www.cimmyt.org/wheat-blast/). This large scale incidence of wheat blast has underlined a concern about the potential spread to other wheat producing regions in South Asia including India, the second largest producer of wheat in the world. This will be a cause of worry in the coming days, unless proactive measures are put in place.

Why should we be concerned about blast disease?

  • The causative agent, a fungus, Magnaporthe oryzae, strikes directly to wither and deform wheat grains, leaving farmers with no time to act
  • The new Bangladesh MoT strain is much more aggressive than earlier strains
  • Wheat blast can spread easily via commercial grain shipments or farmer-to-farmer seed exchanges as it is seed-borne. The conidia, that have the capability of causing disease, can be blown over long distances across farms and borders
  • Fungicides provide partial defense, and must be applied before symptoms appear
  • Outbreaks are occasional and difficult to predict
  • The fungus can grow on other cereal cropsthat include barley, maize, oat and foxtail millet
  • Wheat blast can reduce wheat yields from 10 to 100% depending on genotype, planting time, rainfall and disease severity
  • The pest evolves rapidly, making it difficult to develop a wheat cultivar with durable resistance
  • With porous borders in the South Asian countries, the disease assumes more significance as probability of cross-border movement of pest become high

How do we tackle the enemy?

  • A multi-pronged, multi-dimensional strategy is required as the pathogen cycle and epidemiology of the pest is not fully understood
  • Building genetic resistance, optimum seeding and chemical control can help reduce severity of diseases. Eliminating alternative hosts from the field will minimize the presence of fungus in the field
  • A need for increased surveillance, by monitoring disease appearance, movement and evolution; in coordination with the government, research institutes and private organizations
  • Germplasm screening, identification of experimental wheat lines with durable resistance and development of varieties with durable blast resistance
  • Discovery and characterization of novel resistance genes that can be crossed into superior germplasm. Use of DNA markers associated with resistance genes for marker assisted selection
  • Identification of effective, safe and affordable chemical control measures
  • Strengthening plant quarantine measures governing seed movement in the region
  • Increasing knowledge and awareness about wheat blast amongst scientists, extension workers, decision makers and farmers

Although the wheat blast has not been reported in India, it is still a question of national food security for India and is an emergency as it could have global implications. It is the need of the hour for the Indian government and all wheat stakeholders, both in India and the globe, to be proactive and put forward an integrated solution to prevent this enemy from expanding its presence and making an entry into India and the region!!


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