Developing Weed Resistance in Corn Hybrids

Monday, March 15, 2010

Millions of people in the savannas of west and central Africa rely on maize (corn) as a staple crop, and as an “insurance” food crop at the beginning of the rainy season. A destructive parasitic weed, Striga hermonthica, poses a threat to this valuable crop. Almost 64% of cropland in this area of Africa is affected by the parasite, which causes an average grain yield loss of 68%. Farmers in Striga-infested areas have not yet adopted Striga-resistant hybrids.

Scientists at the International Institute of Tropical Agriculture (IITA) in partnership with scientists in the University of Ibadan in Nigeria and the National Institute of Agricultural Research in Benin Republic investigated the relationship between the genetic diversity of maize inbred lines having different levels of resistance to Striga and the performance of their hybrids under parasite infestation. The results are reported in the March-April 2010 edition of Crop Science, published by the Crop Science Society of America.

The study experimented on all combinations of ten lines of maize with varying levels of resistance to the parasitic weeds in different locations in Africa over three years. Hybrids from two resistant parental lines exhibited the highest level of field resistance, while hybrids from parents with low resistance fared the worst. Hybrids with only one parent with high Striga resistance showed moderate levels of field resistance.

Another important finding was that the genetic diversity of the parental lines did not affect grain yield or other traits among the hybrids. The researchers expect that genetically diverse, Striga-resistant maize crops will provide opportunities to further increase the levels of field resistance to S. hermonthica through breeding.

Such Striga resistant maize hybrids may encourage farmers that abandoned farms due to severe Striga infestation to go back into maize production. This would contribute to food security and provide income-generating opportunities to farmers that depend on maize as an important food crop in Striga infested areas.