Working towards aflatoxin-resistant groundnut varieties

Friday 16 March 2007

Earlier varieties with smaller seeds and technical improvements developed with producers are the keys to quality groundnut. This was demonstrated by a European project conducted by CIRAD, centring on protecting groundnut against aflatoxins in Africa.

Two reference varieties were chosen for study: a cultivar that gives average yields under drought conditions but has good aflatoxin resistance, and another that is higher-yielding but more susceptible to the fungus. Both varieties are widely distributed in Senegal and a large part of sub-Sahelian Africa. The approach taken consisted in studying them under different environmental conditions: under water stress, in the field, in glasshouses, etc. The researchers studied the varieties on an agronomic and physiological, and also biochemical and molecular, level.

One of the main results of the project concerned seed ripening rate: this is a key criterion in groundnut tolerance of aflatoxin contamination. Short-cycle varieties that produce small seeds that ripen quickly are more resistant. Moreover, water stress towards the end of the cycle disrupts the lipid metabolism of the susceptible cultivar more than that of the resistant cultivar. Fatty acid composition differs depending on whether or not the variety is aflatoxin-resistant, and the fatty acid metabolism can thus be assumed to be another parameter linked to groundnut resistance mechanisms prior to harvest.

Furthermore, varieties with improved drought resistance have been developed from an aflatoxin-resistant parent and are currently being disseminated within the production zone. Various studies of good practices that may control contamination before and after harvest have been conducted in conjunction with farmers. They revealed a change in product degradation as it makes its way along the production chain. As a result, the researchers opted to set up a contamination risk analysis system, based on the "from farm to fork" concept, at every stage of the production chain, from production to marketing. In particular, the system concerns the choice of variety, treating crop storage facilities against infestation and the effect of using quicklime or manure to control infestation.

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