Legumes and Striga suicide
IITA, inew
 Morals
aren't at the root of what these legumes do, but their promiscuity and knack for
prompting suicide of weeds are of great help to African farmers.
Legumes make the soil more fertile, and many cause the seeds of a noxious
weed to germinate without the means to survive. IITA scientists are improving
and promoting the virtues of legumes so African farmers will grow more of this
high-protein, low-cost food.
The soybean takes nitrogen from air in the soil and fixes it in nodules on
its roots. To form these nodules, soybean roots need mutually beneficial
associations with bacteria. Most soybean species only make these relationships
with specific strains of bacteria, but some, called promiscuous soybeans, form
nodules with a wide range of bacteria strains, making them much more efficient
at enhancing soil fertility.
 Suicidal
germination controls Striga hermonthica, a flowering parasitic weed that
attacks the roots of cereals and often destroys crops completely, forcing
farmers to abandon fields. To germinate, these Striga seeds need to be
stimulated by chemicals from the roots of crops. A young Striga seedling
has five days to attach itself to a host root and start drawing nutrients and
water. If it doesn't, it dies. Scientists from IITA and other organizations
discovered crops such as soybean, cowpea, and groundnut will stimulate
germination but will not host Striga hermonthica. So if a seed
germinates, it commits suicide.
As part of a project funded by the UK's Department for International
Development, IITA scientists are encouraging farmers in northern Nigeria to
plant legumes and cereals in rotation to lower the amount of Striga hermonthica
seeds in the soil and to improve soil fertility. IITA scientists developed
promiscuous soybeans and introduced them in Nigeria, where soybean production
has tripled over the past 10 years. IITA's soybean breeders are even developing
promiscuous soybeans with enhanced ability to cause suicidal germination of Striga
hermonthica seeds.
The population of Africa is expanding, and farmers are using the land more
intensely to meet demand for food. They can't let fields lie fallow to build up
nutrients and to keep weed infestations manageable, and they can't afford
chemical fertilizers and pesticides. Promiscuous soybeans and suicidal
germination are two practical ways for farmers to keep the land productive and
to nourish families.
More Information:
I.new, International Institute of Tropical Agriculture, IITA. www.iita.org
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