For the much-needed focus they bring on a burning issue, CIMMYT’s Improved Maize for African Soils (IMAS) Project celebrates the Global Soil Week and the International Year of Soils.
Africa’s maize farmers must deal with drought, weeds and pests, but their problems start with degraded, nutrient-starved soils and the farmers’ inability to purchase enough nitrogen fertilizer.
Smallholder maize yields in sub-Saharan Africa are a fraction of those in the developed world, due mainly to the region’s poor soils and farmers’ limited access to fertilizer or improved maize seed. On average, such farmers apply only 9 kilograms of fertilizer per hectare of cropland.
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|Cruz CD, Bockus WW, Stack JP, Tang X, Valent B, Pedley KF, Peterson GL (2012). Preliminary assessment of resistance among US wheat cultivars to the Triticum pathotype of Magnaporthe oryzae. Plant Disease 96:1501-1505.|
|Duveiller E, He XY, Singh PK (2016). Wheat Blast: An emerging disease in South
America potentially threatening wheat production. In: Bonjean A, van Ginkel M (eds)
Wheat World Book, Vol 3. An History of Wheat. Lavoisier, Paris, pp 1107-1122
|Duveiller, E., Hodson, D. and von Tiedemann (2010). Wheat blast caused by Maganaporthe oryzae: a reality and new challenge for wheat research. The 8th International Wheat Conference, Abstracts, 1-4 June 2010, St Petersburg, Russia, VIR, N.I. Dzyubenko, Ed., 247-248.|
|Duveiller E, Hodson D, Sonder K, von Tiedemann, A (2011). An international perspective on wheat blast. Special Symposium, APS-IPPC Joint Meeting, August 6 – 10, Honolulu, Hawaii. Phytopathology 101:S220.|
|Ha X, Koopmann B, von Tiedeman A (2016). Wheat blast and Fusarium head blight
display contrasting interaction patterns on ears of what genotypes differing in
resistance. Phytopathology dx.doi.org/10/1094/PHYTO-09-15-0202-R.
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Of that small amount, often less than half is captured by the crop; the rest is leached deep into the soil where plants cannot recover it or otherwise lost. But all is not bleak, and here are some of the solutions from the Improved Maize for African Soils Project.
One of the most fearsome and intractable in recent decades is wheat blast, caused by the fungus Magnaporthe oryzae.
- It directly strikes the wheat ear and can shrivel and deform the grain in less than a week from first symptoms, leaving farmers no time to act.
- Fungicides typically provide only a partial defense. They are also often hard to obtain or use in the regions where blast occurs, and must be applied well before any symptoms appear—a prohibitive expense for many farmers.
- Blast appears sporadically on wheat and grows well on numerous other plants and crops, so rotations do not control it. The irregular frequency of outbreaks also makes it hard to understand or predict the precise conditions for disease development, or to methodically select resistant wheat lines.
- The fungus is physiologically and genetically complex, so even after more than three decades, scientists do not fully understand how it interacts with wheat or which genes in wheat confer durable resistance.
Map showing Wheat Blast Regions
First sighted in Brazil in 1985, blast is widespread in South American wheat fields, affecting as much as 3 million hectares in the early 1990s and to present seriously limiting the potential for wheat cropping on the region’s vast savannas. It appeared in the USA in 2010. Because the pathogen is seed-borne, most wheat cultivars are susceptible, and fungicides are ineffective at controlling it, many experts fear its eventual spread to major wheat regions worldwide with conditions analogous to those of South America, such as Ethiopia. A severe, surprise outbreak of blast in seven key wheat districts of southwestern Bangladesh in early 2016 has raised the specter of its spread to other parts of South Asia—home to more than 300 million undernourished people and whose inhabitants consume over 100 million tons of wheat each year.
Wheat Researchers at work in field and lab
As a global leader in research for development in wheat and maize and wheat- and maize-based farming systems, CIMMYT led the launch in 2011 of a global Wheat Blast Consortium comprising 13 institutions from Europe and the Americas. Partners are rushing to develop and share integrated control measures, including:
- Improved wheat varieties that carry genetic resistance to M. oryzae. Promising lines are being tested.
- Global monitoring of disease appearances, movement, and evolution, in coordination with local governments and research agencies, as well as predictive models.
- Advanced studies on potentially effective, safe, and affordable chemical control measures.
- Genetic and epidemiological research to strengthen knowledge of the fungus and its interactions with wheat and other host plants.
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