SATrends Issue 78 May 2007
  • Farmers of the Future learn how to invest
  • Body count for a virus
  • Peanuts without poison

  • 1. Farmers of the Future learn how to invest

    Agriculture education of primary school children is one of the many activities carried out in an experiment on integrated rural development in the Sadoré village near ICRISAT's Niamey campus. This will hopefully create a new generation of farmers open to innovation, aware of the environment and market oriented. The program is called "Farmers of the Future" (FOF).

    As a start, an African Market Garden (based on low-pressure drip irrigation) was installed at the Sadoré village school to teach the children modern approaches of vegetables production. ICRISAT also built a nursery for fruit tree production, and is planting trees of value by the school. An ICRISAT staff member and a Peace Corps volunteer follow-up on the activity, and cooperate strongly with the school director and the village chief. Fifty children aged 12-14 participate in the FOF. In the first production season the children saved 28,685 Francs cfa ($57) from sales of vegetables.

    Girl student at the back suggests they buy school uniforms.

    The children are taught investment strategies. To the question, "What to do with so much money?" the students came up with several ideas - the purchase of pens and notebooks, a school party, a field trip, new uniforms or simply saving the money. The volunteers highlighted the importance of the garden and the advantages of making profits from the nursery. The students eventually decided they would need watering cans for their nursery, and weighed the options between metal and rubber watering cans.

    They are given the options - the price of one metal watering can (which will last a year) is 2500 FCFA. The price of a rubber watering can (which will last for three years) is 8000 FCFA. At first, the students wanted to get the rubber one, but were advised thus: if they bought a metal can, and had to replace it each year for three years, the money spent would be less than 8000 FCFA. In addition, if they spend less now, they will have extra money to work with. This difference became more evident when the students considered buying two rubber cans (16000) or two metal cans (5000). The students participated in the mathematical calculations to understand these concepts. They finally decided to buy metal watering cans. This was their first step towards market orientation.

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    2. Body count for a virus

    Employing biocontrol approaches that use natural enemies or disease causing microbes to control plant pests is a popular strategy today. One infamous pest, the legume pod borer or the cotton bollworm, Helicoverpa armigera, is the most devastating pest of several crops.

    The virus Helicoverpa armigera nucleopolyhedrovirus (HaNPV) that naturally infects H. armigera, has been isolated and is employed as a 'viral insecticide' against this pest. Aqueous suspension of HaNPV extracted from diseased larvae is used in a spray on crops. When larvae feed on the virus-laced plant parts, the HaNPV enters the insect gut and invades its body, which leads to cession of feeding, flaccidity and liquefaction of body tissue. NPV can kill pest larvae in 5-6 days.

    Mass production of HaNPV insecticide is simple and widely produced even at the village level. Healthy H. armigera larvae reared in the laboratory or collected from the fields are fed with a low dose of HaNPV and the virus produced in the insect is harvested. Its concentration is estimated by counting polyocclusion bodies (POBs), which are aggregates of HaNPV particles encased by the viral polyhedrin protein.

    Clockwise from top left: Scanning electron micrograph of POBs; HaNPV infected H. armigera and ELISA for POB estimation.

    The effectiveness of the viral insecticide is critically dependent on the concentration of POB, which is expressed as larval equivalent (LE). A standard 1 LE stock preparation at ICRISAT consists of 6 ×109 POBs/ml. A light microscope fitted with a hemocytometer is used to estimate the POB concentration. However, this procedure has a low-detection efficiency, poor specificity, is laborious, and requires considerable skill. Thus, many HaNPV products produced are ineffective under field conditions. To overcome this, ICRISAT developed an enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of POBs.

    Polyclonal antibodies were produced against the POBs purified from the diseased larvae. In the ELISA test, POBs present in the HaNPV insecticide preparation binds to the ELISA plate. Then POB-specific antibodies are added, followed by the detection of POB-antibody complex using an enzyme-labeled reporter antibody. Finally, the enzyme-labeled reporter antibody is detected using a colorimetric reaction that provides an estimate of the original POB concentration. This test is highly specific and can detect concentrations as low as 50 POBs/ml or 15 ng/ml of HaNPV polyhedrin protein. The test is simple to perform, cost-effective and is convenient for monitoring the quality of the HaNPV viral insecticides.

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    3. Peanuts without poison

    Groundnuts (aka peanuts) are prone to infestation by two closely related fungal species, Aspergillus flavus and Aspergillus parasiticus, which belong to a highly toxic group of mycotoxins known as aflatoxins. Aflatoxin contamination of groundnut is a major human and animal health hazard and is one of the most important constraints to groundnut trade. Aflatoxin is a natural toxin known to cause cancer, suppressing immunity and interfering with nutrient uptake. Aflatoxin invades groundnuts during production or soon after harvest and is more prevalent in groundnuts exposed to end-of-season drought stress.

    Groundnut infested with aflatoxin.

    ICRISAT has developed several technologies - genetic resistance, agronomic practices, biological, and biotechnological methods as components of integrated disease management - to reduce the risks of aflatoxin contamination. In 2003, ICRISAT in collaboration with the Malian Agricultural Research Institute (Institut d'Economie Rurale (IER)) initiated a farmer participatory evaluation of best bet agronomic and post harvest management practices in the regions of Kayes and Kolokania. The program was aimed at minimizing aflatoxin through research, development and promotion of appropriate on-farm and post-harvest management practices. In these locations, groundnut is grown purely under rainfed conditions with limited external inputs, and is prone to end-of-season drought. Groundnut-based cropping systems constitute an important source of livelihood for the farmers in these areas as the pods provide the much needed cash income, and the haulms are a valuable source of fodder.

    Initial monitoring of farmers produce in the two districts showed very high contamination averaging 264 parts per billion (ppb). The groundnut paste consumed by every Malian family irrespective of economic status was also highly contaminated to levels far above acceptable health risk levels.

    After three consecutive seasons of trials /demonstrations of pre-harvest agronomic practices (application of lime, manure and crop residues) as well as the best bet and harvesting pro techniques, more than 50% of the farmers are now producing groundnuts that are nearly free of aflatoxin, which is now at levels that are acceptable for human consumption (see graph).

    To increase awareness about the dangers associated with aflatoxin contamination, field days were organized for farmers, extension workers, processors and traders. This was further enhanced through brochures in local languages (French and Bamabara). Effective aflatoxin control requires awareness and information among all participants from production, through processing, to marketing and eventual consumption and consequent actions.

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