Author: Naresh Barma
New biotic stresses have emerged around the globe over the last decades threatening food safety and security. In 2016, scientists confirmed the presence of the devastating wheat-blast disease in Bangladesh, South Asia–its first occurrence outside South America. Severely blast-affected wheat fields had their grain yield wiped out. This poses a severe threat to food security in a densely-populated region with millions of poor inhabitants where wheat is a major staple crop and per capita wheat consumption has been increasing. As an ex ante impact assessment, this study examined potential wheat-blast scenarios in Bangladesh, India, and Pakistan. Based on the agro-climatic conditions in the epicenter, where the disease was first identified in Bangladesh in 2016, this study identified the correspondingly vulnerable areas in India, Pakistan and Bangladesh amounting to 7 million ha. Assuming a conservative scenario of 5–10% for blast-induced wheat production loss, this study estimated the annual potential wheat loss across the sampled countries to be 0.89–1.77 million tons, equivalent to USD 132–264 million. Such losses further threaten an already-precarious national food security, putting pressure on wheat imports and wheat prices. The study is a call for action to tackle the real wheat-blast threat in South Asia.
Wheat blast or ‘brusone,’ caused by the ascomycetous fungus magnaporthe oryzae b.c. Couch (syn. Pyricularia oryzae cavara), was first identified in 1985 in brazil. M. oryzae is composed of a range of morphologically identical but genetically different host-specific pathotypes that are specialized for infecting rice (oryza pathotype), wheat (triticum pathotype - mot), perennial and annual ryegrass (lolium pathotype), foxtail millet (setaria pathotype), and many other graminaceous hosts. Isolates from different hosts are genetically distinct, although cross infection occurs to some extent. Wheat blast has become a serious biotic constraint to wheat (triticum aestivum l.) production in parts of the warmer wheat growing areas of the southern cone region of south america, causing yield losses of 10 to 100% in recent years (duveiller et al. 2016). Wheat blast was observed for the first time outside of south america during the 2015-16 cropping season in the districts of kushtia, meherpur, chuadanga, jhenaidah, jessore, barisal, bhola, and several other districts in the south of bangladesh. Infected plants showed the typical wheat blast symptoms with the spike becoming partially or completely bleached with the blackening of the rachis in a short span of time. Examination of diseased plants showed the presence of elliptical, grayish to tan necrotic lesions with dark borders on the leaf often mixed with spot blotch disease lesions. Additionally, in some fields, blackening of lower nodes was observed. Grains from blast-infected heads were small, shriveled, deformed, and had low test-weight leading to serious yield losses. Diseased plants were collected and brought to the wheat research centre, bangladesh agricultural research institute, dinajpur, for further investigation. Grayish mycelium of the fungus taken from the infection point on the rachis of several independent spikes was observed. Incubation of several infected spikes/leaves in a 3-layered moist blotter at room temperature less than 12 h light/darkness cycle for 5 days led to the production of pyriform conidia. Morphobiometrical characteristics of the typical pyriform (pear-shaped) and 2-septate hyaline conidia were in agreement with the identification of the fungus as m. oryzae (subramanian 1968). The air-dried spike samples have been kept in cold storage and several infected spikes were sent to the usda-ars, fdwsru laboratory in the united states for characterization of the pathogen. There, the presence of m. oryzae in the infected samples was confirmed based on morphobiometrical analysis, and strains were preserved in the fdwsru permanent wheat blast strain collection. Molecular analysis with mot-specific markers and comparative genome analysis of isolates (bdbar16-1, genbank accession no. Lxon01000000; bdjes16-1, lxoo01000000; bdmeh16-1, lxop01000000) confirmed that the wheat blast observed in bangladesh is caused by mot pathotype and has strong genetic identity to a strain from south america (b71, lxoq01000000). This first incidence of wheat blast was significantly widespread accounting for approximately 15% of bangladesh’s total wheat area. This large scale incidence of wheat blast has underscored a concern about the potential spread of wheat blast to other wheat producing areas in bangladesh, south asia, and beyond.
The first occurrence of wheat blast in 2016 threatened Bangladesh's already precarious food security situation. The Bangladesh Agricultural Research Institute (BARI), together with the International Maize and Wheat Improvement Center (CIMMYT) developed and released the wheat variety BARI Gom 33 that is resistant to wheat blast and other common diseases. The new variety provides a 5–8% yield gain over the available popular varieties, as well as being zinc enriched. This study examines the potential economic benefits of BARI Gom 33 in Bangladesh. First, applying a climate analogue model, this study identified that more than 55% of the total wheat-growing area in Bangladesh (across 45 districts) is vulnerable to wheat blast. Second, applying an ex-ante impact assessment framework, this study shows that with an assumed cumulative adoption starting from 2019–20 and increasing to 30% by 2027–28, the potential economic benefits of the newly developed wheat variety far exceeds its dissemination cost by 2029–30. Even if dissemination of the new wheat variety is limited to only the ten currently blast-affected districts, the yearly average net benefits could amount to USD 0.23–1.6 million. Based on the findings, international funder agencies are urged to support the national system in scaling out the new wheat variety and wheat research in general to ensure overall food security in Bangladesh and South Asia.
Adoption Biofortified Climate Analogue Ex-Ante Net Benefit Vulnerable Wheat Blast Zinc Enriched CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA WHEAT PLANT DISEASES RESISTANCE VARIETIES FOOD SECURITY NUTRITION AGRICULTURAL SCIENCES AND BIOTECHNOLOGY FOOD SECURITY NUTRITION