The elephant and the peanut
Applying map technology to reduce a public-health menace
“You don’t have to describe to a child what an elephant is when he can see one.” This proverb from Ghana could be explaining the sheer visual power of maps, but could also be describing a mighty and silent killer.
Have you ever wondered why you stare at your own backyard on Google Earth? One effect of maps on scientists in West Africa has been a growing interest in aflatoxins—toxic substances produced by the Aspergillus fungi that infest groundnuts (peanuts) and other crops. Aflatoxins are among the most potent carcinogens known, and particularly affect the liver.
So what does this have to do with maps?
Weather and field conditions control how quickly the fungus grows in any particular harvest. And these environmental and management conditions can be monitored by satellite.
It turns out that peanut pods are particularly susceptible if they matured during a dry spell – weaker shells allow the fungus in. Also, if they sit on the ground after harvesting when it’s damp, the fungus just explodes. Quite often you can see the green powdery fungus in the peanut shell. But it doesn’t have to be visible to be dangerous.
Some weather satellites can help predict harvest time and moisture levels. Combined with very high-resolution imagery—satellite pictures that allow you to zoom in very close and see inside fields, they help tell whether a particular field has a high, medium, or low risk of aflatoxin in the harvest. That means they show critical places where farmers should rush the crop off the field to dry.
Figure 1: Duration of peanut pod residence in the “aflatoxin risk zone” (roughly between 10-30% moisture in kernel) results in low (green), medium (yellow) or high (red) contamination in harvest.
Groundnut varieties resistant to aflatoxins are in development. For now, the most important defense is to remove the crop from damp ground.
It’s not that the farmers leave them there out of neglect. Groundnuts often come last. Cotton may get ruined if left in the field — and it’s cash, so it’s more urgent. After that come the staples millet and sorghum. Only then can the farmer attend to the groundnuts.
Most people have no idea of the dangers of aflatoxin. As with tobacco, you usually don’t see the effects till many years later. It’s well documented in medical literature, but the problem is hugely underestimated. Aflatoxin delays development. And it’s a silent killer.”
With hard work and funding, that particular elephant might be tamed.
For more information contact: p.traore@cgiar.org
back to top 
A climatic whodunit!
Are farmer perceptions about climate change correct?
Convincing farmers in Eastern Kenya of climate change is a little bit like preaching to the converted. They already believe that the climate of today is very different from 30–40 years ago. For example, almost all of the 124 farmers interviewed in the three districts of Kitui, Mwingi and Mutomo believe that there is less rain than before, that temperatures are higher, rivers flow less rapidly and rainfall is more erratic resulting in reduced crop yields and frequent crop failures.
While climate change is a reality, and it appears that temperatures in Africa are warming, there is little direct evidence to link global climate change to local level patterns, especially rainfall. Climate change isn’t necessarily responsible for the changes in crop productivity as perceived by farmers.
A look at the actual historic data in the three districts of Eastern Kenya show that the frequency of years with a rainfall greater than the long-term average of 1957–2006 are higher during the last two decades (see Figure 2).
Figure 2: Number of short rainy seasons (Oct-Dec) in each decade that received more rain than the 1957-2006 long-term average of
296 mm at Katumani, Eastern Kenya.
The data also shows that there is a decline in yields over the same period of time and other research shows that this is most likely due to land degradation and the practice of low-input agriculture rather than climate change. Farmers, however, do not seem to make this distinction. They seem to judge a season as good or bad based on the performance of the crop in their fields and yields can be poor for a variety of reasons such as high weed infestation or loss of nutrients through leaching and not just inadequate rainfall. For example, only 47% of respondents ranked the extremely good short rain season of 2006 as being good.
Why exactly does this matter? It matters because farmers’ perceptions about the climate decide their behavior. Even though farmers list climate variability (inadequate moisture) as a major constraint affecting crop production, they did not let this influence their choice of crop and management practices. Instead of choosing varieties that are able to better withstand erratic rainfall or following management practices such as applying fertilizer, farmers blamed the climate over which they have no control. This results in a huge gap between the actual potential of a farmer’s field and what the farmer is able to achieve. The key to bridging this gap is to help farmers make decisions based on an objective assessment of the situation rather than relying on subjective perceptions.
For more information contact: k.p.rao@cgiar.org.
back to top
Reap as you sow
Efforts to create a broader genetic base for groundnuts
The July 2008 issue of SATrends carried a story called “Evolution fast forward”, which explained the development of “synthetic groundnuts” within a major initiative where scientists are developing new sources of Arachis hypogaea, commonly known as groundnuts or peanuts.
“As you sow, so you shall reap” goes the saying. This can be applied to the developments taking place at ICRISAT, where scientists continue to develop new sources of groundnut. It is evident that
A. hypogaea, with 40 chromosomes (2n=40), evolved a few thousand years ago from one or a few diploid ancestor/s, with 20 chromosomes (2n=20). Well, many other crops such as wheat and brassica (mustard) have also evolved through such a polyploidy route. But unlike these crops, even the modern day groundnut has a narrow genetic base, which means variability is low in the crop. As a consequence of this the crop is susceptible to a range of biotic and abiotic stresses.
In order to broaden the genetic base and introduce traits of importance, scientists undertook the synthesis of A. hypogaea. Many diploid Arachis wild species were used to synthesize new sources. As a result, there are more than 10 new sources of A. hypogaea and some of these are being used to broaden the genetic base of groundnut and introduce new traits of interest.
In the past, one such synthetic groundnut, which was synthesized by Dr Simpson of Texas A & M, USA, was used by breeders to introduce nematode resistance in groundnut. Similarly two synthetic groundnuts, which were developed by the Generation Challenge Program initiative, are being used by breeders to broaden the genetic base.
A beginning was made in 2006 at ICRISAT, a thorough molecular study was made to study diversity of the Arachis species. Scientists made selected crosses from which new sources of A. hypogaea were developed. These are different from the presently available synthetic A. hypogaea. In a quick-fix test called the detached leaf technique to test for late leaf spot resistance (LLS), synthetic groundnuts showed high levels of resistance. As a result, we now have many more new sources of synthetic groundnuts from ICRISAT, which are being used by breeders to introduce LLS resistance, amongst other traits, and also broaden the genetic base. So far the crossing initiative has been both exciting and remunerative with good recombination between cultivated and synthetic groundnuts.
For more information contact: n.mallikarjuna@cgiar.org
back to top
