News - February 8, 2013

Pesky seed

How do you increase food security for the hungry populations of developing countries? This question is at the centre of attention in Wageningen this year. Albert Sikkema on the trail of ‘our’ contribution to global food security.

Striga is a parasitic plant that lives off other plants. Striga seeds lie in unbelievably large quantities in the African soil, waiting to germinate. This process is activated by signal substances given off by agricultural crops. Then they overwhelm and strangle the crop, jeopardizing the food supply of 300 million Africans. So if you can get rid of this parasite, you can make a nice contribution to improving food security.
Weeding is an impossible task because you have to avoid activating the Striga seeds with the signal substances. Harro Bouwmeester is doing fundamental research on these substances, the strigolactones. His aim is to find out which genes in the plant make the signal substances and whether it is possible to restrict their manufacture. 'Once you know the mechanism, you can target an intervention much more precisely,' he believes.
The underlying problem is the poor African soil. Development workers have known for years that Striga thrives on poor soils and that you need fertilizer to keep the parasite under control. But artificial fertilizer is scarce and expensive. Bouwmeester has made some progress, however.
During field trials on sorghum in Mali last year, it appeared that a small dose of phosphate per plant cut the germination of Striga by 40 to 84 percent. This increased the grain harvest by 47 to 142 percent. Bouwmeester conducted these trials together with Wageningen alumnus Tom van Maurik, alias Doctor Striga. Van Mourik works at the ICRISAT research station in Mali, where he is in a position to spread the word among Sahel farmers.
So is the Striga problem solved? No. Bouwmeester's group also did field trials on maize in Kenya. There a dose of phosphate produced a much smaller reduction in Striga and increase in the harvest. Bouwmeester suspect that whether phosphate helps depends on the composition of the soil. Further research is needed.
What is clear is that farmers in the Sahel need artificial fertilizer (phosphate) to increase food security. Their poverty-stricken organic farming methods are woefully unproductive. A tiny dose of phosphate with the sorghum seed combined with the application of compost is enough to have an effect, they learn at Van Mourik's farmer field schools. Nice to see that this knowledge is trickling down to farmers in the Sahel, with Wageningen as partner.