The Nigerian National Variety Release Committee (NVRC) has released the first generation of maize hybrids, resistant to metsulfuron methyl herbicide, that are also endowed with resistance to the noxious parasitic weed Striga hermonthica.
The hybrids were developed by the International Institute of Tropical Agriculture (IITA) in partnership with DuPont Pioneer Seeds using conventional breeding with funding from IITA and the Integrated Striga Management in Africa (ISMA) project as part of strategies to control S. hermonthica in maize.
The hybrids were released as P48W01 and P48W02 and are recognized as IITA IR-Maize Hybrid 2 and IR-Maize Hybrid 4. The hybrids have a yield potential of up to 5 t/ha under Striga infestation in comparison with local varieties that produce less than 1 t/ha in such conditions.
“These hybrids are the product of introducing a single nuclear gene that confers resistance to imidazolinone herbicides, including metsulfuron methyl (MSM), into inbred lines with known field resistance to S. hermonthica,” Dr Abebe Menkir, IITA Maize Breeder, said.
Recent baseline studies conducted under the ISMA project showed that farmers ranked Striga as the number one constraint to maize production in northern Nigeria, with 50 to 100% of the households reporting Striga incidence in their farms. The parasitic weed infests more than 9 million ha planted to millet, maize, and sorghum in Nigeria and severely lowers the production capacity of these crops.
Dr Menkir said yield losses in maize from damage by S. hermonthica varied from 20 to 80% among subsistence farmers, but 100% loss could occur in susceptible cultivars under severe infestation in marginal production conditions.
The released herbicide-resistant hybrids allow seeds to be planted that have been treated with low doses of metsulfuron methyl herbicide. This targets S. hermonthica before or at the time of its attachment to the maize root, killing the parasite underground before it inflicts damage on the crop. These hybrids can thus be used to deplete the Striga seed bank in the soil and minimize yield losses in subsequent cereal crops. MSM-reated seeds of these hybrids can be integrated into the diverse farming systems in Nigeria because the herbicide effectively controls the parasite at a low rate of application.
The ISMA project works with the private sector to catalyze the process of producing and marketing treated seeds of herbicide-resistant maize hybrids to smallholder farmers in Nigeria to control S. hermonthica.
Other collaborating partners engaged in extensive testing of these hybrids include the Institute for Agricultural Research (IAR) and Agricultural Development Programs in Bauchi and Kano States.
The ISMA project is being implemented by IITA in partnership with CIMMYT, icipe, BASF Crop Chemical, AATF and national partners in Kenya and Nigeria.