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Agrobiodiversity / / Mapping cassava beyond deception

Mapping cassava beyond deception

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Measuring “descriptors” of cassava varieties at a three-week training workshop in Vietnam.

If you know what a lanceolate is, then this blog post is probably not for you. You probably also know what ovoids and elliptics are as well. If you’re still reading, the word “linear” might be more familiar ground.

All the above are shapes. More specifically, they are possible shapes of the central leaf of a cassava plant. Remarkably precise, you might think. But given that descriptions for pinning down cassava varieties span three pages of A4, such guidance is more a relief in such a sea of possibility.

Because cassava plants are rather deceptive. They might look like each other in the field – and their narrow genetic background does make them difficult to tell apart – but when you get down to it, there’s petiole color, which could range from purplish green to reddish green or greenish red, orientation of petiole, color of leaf vein – and a startling array of other possible descriptions to consider.

Precision techniques

It’s no wonder researchers and farmers need a bit of help in telling the difference between cassava varieties. Currently, different countries have different guides and methods of variety description, and some cassava varieties are not recorded, says Manabu Ishitani, a molecular biologist leading the three-week capacity building program in Vietnam.

Researchers from Thailand, Laos, Vietnam and Cambodia identify different varieties of cassava.

Researchers from Thailand, Laos, Vietnam and Cambodia identify different varieties of cassava.

There are swathes of cassava fields in Southeast Asia which are unaccounted for because they have been wrongly characterized. “A common description of cassava varieties for the whole region, a “descriptor guide”, will build a set of reference points to track varieties in Southeast Asia, while building capacity in reliable methods of identifying them across the region,” he said.

Descriptor guides will help researchers evaluate the genetic diversity of cassava, which together with ID testing in the laboratory, will enable them to map out what varieties are grown where.

This information can steer research towards demand-oriented, popular varieties, and build the foundations of a regional “seed” or planting material system, to ensure improved and disease-free planting material is available to farmers when needed.

The guides will also benefit farmers who know varieties they really have in their fields. Certain environmental conditions including soil type, temperature, rainfall – even markets – can be matched with varieties that perform best in those conditions to improve yields and income.

Knowing what varieties farmers can plant will also help ward off pests and diseases to which their harvests may be susceptible.  This could make the difference between a good or disastrous harvest for farmers who might be at risk of losing their harvest.

On-the-job training

Capturing different varieties in the field for a complete guide of cassava descriptions.

Capturing different varieties in the field for a complete guide of cassava descriptions.

Armed with rulers, knives and cameras, the group of trainee researchers tread through a green canopy of cassava fields on the outskirts of Hanoi to scrutinize, prod and document what different varieties look like.

The training, at Vietnam’s Agricultural Genetics Institute, will equip the international group of researchers in how to develop lists for cassava varieties released or cultivated in each country, selected botanical and agronomical descriptors most relevant in the region, and molecular markers for genetic descriptors to improve precision.

This research is part of a wider project in “On-the-job research capacity building for sustainable agriculture in developing countries,” which started in 2011, funded by the United Nations University Institute for sustainability and peace through Japan’s Ministry of Agriculture, Forestry and Fisheries.

New complementary research at CIAT just launched, using DNA fingerprinting techniques, will quantify the spread of cassava varieties in Asia, to trace the impact of research by finding out which varieties have been adopted most widely. But that’s the topic of another post.

And in case you’re still wondering, botanically speaking, a “lanceolate” is a leaf in the general shape of a lance, an “ovoid” is shaped like an egg, and “elliptic” means a closed, symmetric curve shaped like an oval. Just so you know.

Picture credits: Georgina Smith / CIAT

Download the Stewardship Report 

Click here for pictures of the training workshops

 

 

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  • Reinhardt Howeler: Thanks, Keith. It was a pleasure writing this book as it brought back so many good memories of working with cassava, both in Latin America and in Asia. I was lucky that the Nippon Foundation suggested that I write this book and financed its publication. They also wanted a simplified version for farmers and extension workers that could be translated into various languages. The English version of this new book is now going to press in Hanoi, while the Khmer and Vietnamese translations are also ready for printing and the Thai and Chinese translations are still being worked on. In case you are interested in the English version, let me know. My email address is still r.howeler@cgiar.org. And let me know where you are working now and what you are doing. Reinhardt
  • Peter de Vroome: Great invention! Could be very usefull in our research in fast detecting CFSD in our planting material. Is this kit already for sale? Peter de Vroome phytopathologist Centre for Agricultural Research in Suriname (C.E.L.O.S.)
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  • Keith Fuglie: An impressive publication! Reinhardt Howeler has done an incredible job of summarizing lessons from nearly 30 years of work on cassava improvement in Asia. This very successful collaboration between CIAT and national research programs demonstrates what can be achieved through modest but persistent investment in agricultural research, even with a relatively neglected crop grown primarily by poor farm families in marginal environments.
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  • Kellan: i am also working on ppd on cassava. can you please help me find find a suitable protocol to analyse ppd.
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