A flowering witchweed (Striga asiatica L. O. Krantz) in a conventionally-ploughed maize field on sandy soils in Madziwa, Zimbabwe. Photo credit Christian Thierfelder, CIMMYT.
The world produces more maize by weight than any other cereal crop. Maize, also known as corn, is a staple food in many countries. But farmers growing corn face many challenges, such as drought, diseases, and pests.
For example, in sub-Saharan Africa, 20 to 80% of maize yields may be lost because of a semi-parasitic plant, Striga. In areas infested with Striga, farmers may even lose their entire crops.
In a new study, researchers from southern Africa identified several varieties of maize resistant or tolerant to Striga. Importantly, these varieties also have improved nutritional content, particularly protein.
The combination of Striga tolerance and improved nutrition is key. Farmers, as well as local populations, will benefit, says Peter Setimela, a study co-author. Setimela is a scientist at the International Maize and Wheat Improvement Center (CIMMYT) in Harare, Zimbabwe.
Striga infestations can force small farmers in sub-Saharan and southern Africa to abandon their farms. “Striga is known to affect fields that have poor soil fertility. Its seeds can stay in the soil for more than 15 years,” says Setimela. “Many small farmers can’t afford to buy chemicals to control Striga. They may also be unable to buy chemical fertilizers.”
Having access to varieties of maize that can tolerate Striga will benefit these farmers. They will be able to continue farming and growing maize in areas with Striga.
The improved nutritional content of these maize varieties will also help. The varieties have a wider variety of amino acids, the building blocks of protein.
“Typically, maize is poor in essential amino acids. Human and animal bodies can’t make these amino acids. They have to be obtained from food,” says Setimela. “Lack of essential amino acids can impair growth and development. It can also weaken the immune system.”
Many rural populations depend on maize as a staple food. “But these populations often have limited access to protein sources, such as eggs, meat, and dairy products,” says Setimela. “If varieties of maize can provide high-quality protein, these populations will benefit.”
Setimela and colleagues tested both typical and high-protein varieties of maize for Striga resistance in the lab and field.
A flowering witch weed (Striga asiatica L. O. Krantz) at Goromonzi district, Zimbabwe in maize field under conservation agriculture. Photo credit Isaiah Nyagumbo, CIMMYT.
Controlled conditions, such as those in the laboratory, allow researchers to conduct tests that may not be possible in the field. But “ultimately, crops will be grown in farmers’ fields,” says Setimela. “We ensured that the results from controlled environments also apply to field conditions.”
Field experiments were carried out in three locations in Zimbabwe with diverse conditions. The researchers tested eight high-protein varieties and four typical varieties of maize. They measured several plant characteristics, including yield, height, vigor, and kernel weight.
Researchers found four varieties of high-protein maize that also showed high levels of Striga tolerance and high yields.
“These varieties will provide options to farmers in areas with Striga,” says Setimela. “They will improve food security and nutrition.”
Read more about this research in Crop Science. The European Union funded this research through Welthungerhilfe (SIMBA Project). The German Academic Exchange Service (DAAD) provided a partial scholarship to the first author. CIMMYT-Zimbabwe and the CGIAR Research Program on Maize (MAIZE) provided scientific support; Seed Co, and Mukushi Seeds provided germplasm.