Mapping cassava beyond deception
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.
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.
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.
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.
Photos and text by: Georgina Smith (CIAT)