Without Protection from Insects, No Field of Dreams for Kenyan Maize Producers

As a young boy, Stephen Mugo worked in his father's small maize plot on the southern slopes of Mt. Kenya. With care, that land fed the family and its dreams, paying the school fees and allowing Mugo's parents to build up a village shop. Even so, farming had its risks, particularly the havoc that insects could wreak on the maize field and the family's daily life.

"The stem borers would hit the crop around knee-high stage, inflicting damage that, if not checked, would mean very little yield," Mugo recalls. "At harvest, during seasons of heavy infestation, we had to stoop to recover plants that had lodged on the ground, and the maize would often be rotten."

"When my parents could afford it, they would purchase DDT powder in bright yellow packets, and we would spend hours applying the dust into the funnel of every single maize plant. We were unaware of the dangers we faced and did not use any protective measures. And as we all know, DDT has long since been banned."

Still Working against Insects, But on a Larger Field

Thirty years later, Mugo still seeks to banish destructive insects, but his dream to raise maize production is now played out on fields across Kenya. As CIMMYT maize breeder and coordinator for the Insect Resistant Maize in Africa Project (IRMA), a collaborative effort between the Kenya Agricultural Research Institute (KARI) and CIMMYT, Mugo works to produce maize that can resist these insects on its own.

The IRMA Project, funded through the Novartis Foundation for Sustainable Development, was launched with a Stakeholders Meeting in Nairobi in March, 2000. In attendance were representatives of farmers', women's, and church associations; extension services; various ministries; the private sector; and a contingent of Kenyan print and broadcast media. Director of Agriculture and Livestock Wilfred Mwangi, on leave from the CIMMYT Economics Program, opened the meeting.

Mwangi was followed by Minister of Agriculture Christopher Obure, who declared, "Agricultural productivity has not kept up with population growth, and food security therefore remains a top government priority. This trend is accentuated by the increasing drought spells of recent years. The poorer segments of our population suffer especially hard."

Building on this point, Obure stated that small-scale agriculture plays an important role in the government's poverty eradication and food security plans. Agricultural intensification was the key, he emphasized, but with that comes increased insect pest pressure. Referring to the IRMA Project, he noted that reducing losses to insects would "result in an increased and more stable maize production, improving our food security substantially."

A Project with a Purpose

A variety of insect pests eat through Kenya's maize crop, but stem borers are among the most pernicious. Once inside a maize stalk, borers are impervious to conventional insecticide applications and cannot be removed by hand. Damage estimates vary from year to year, ranging from 15 to 40% of the national maize crop. Some smallholders lose entire fields to the pests. Several insecticides widely used against borers were pulled off the market due to safety concerns. How can farmers possibly cope?

Scientists from KARI and CIMMYT designed the IRMA Project to address the problem. Over five years, they will use conventional and biotechnological means to develop insect-resistant maize for major Kenyan production systems and insect pests. They will also:

• establish procedures to provide insect-resistant maize to resource-poor farmers;
• assess the impact of insect-resistant maize in Kenyan agricultural systems;
• transfer skills and technologies to KARI and Kenya to develop, evaluate, disseminate, and monitor insect-resistant maize; and
• plan, monitor, and document project processes and achievements for dissemination to other developing countries, particularly in East Africa.

Multidisciplinary Partnerships Find the Right Approach

The IRMA Project calls on CIMMYT and KARI expertise in maize breeding, agricultural economics, biotechnology, entomology, and communications. To develop solutions that are right for Kenya, researchers are gathering baseline data and soliciting input from farmers and other key stakeholders. In 2000 they initiated participatory rural appraisals (PRAs), yield loss assessments, an analysis of the maize market in Kenya, and environmental impact assessments (particularly in regard to non-target insects, potential stem borer parasitoids and predators, and soil ecology).

In the rural appraisals, CIMMYT economist Hugo de Groote and KARI economists collect information on what farmers like in a maize variety and what they think about insect pest problems. These baseline data will help researchers assess IRMA's economic impact. The PRAs also provide information on agronomic and consumer characteristics that will help breeders produce varieties tailored to Kenya's agricultural zones. To economize on time and effort, crop yield loss assessments are conducted in a representative subset of the PRA locations.

Entomologist Josephine Songa of KARI, meanwhile, is investigating a very different population the insects and soil organisms residing in the fields of Mtwapa and Kakamega, two of the five maize-growing regions where crop loss assessments will be made. Songa, working with KARI scientists and extension staff, set a variety of traps to capture the flying and crawling insects typically found in farmers' fields. Research and extension staff regularly collect the catch in these traps, thus obtaining the baseline data for assessing impact on insect populations at a later date. Soil cores will be drilled at the respective sites at four stages of maize growth, and the range and density of organisms in the samples will be analyzed, again serving as a baseline for later assessments.

An exploratory experiment to determine the effectiveness of Bacillus thuringiensis (Bt) genes against Kenyan stem borers became the proving ground for project researchers to navigate through, and comply with, important regulatory procedures. The project applied to import fresh leaf tissue from transformed Bt maize plants. The importation of such materials is rigorously reviewed. Following approval by the KARI Institutional Biosafety Committee, the application was forwarded to the Kenya National Biosafety Committee (NBC). It is anticipated that the NBC will authorize the Kenya Plant Health Inspectorate Service to issue the import permit later in 2000. Importing only leaf tissue, not live plants or maize cobs, means that there is no possibility of inadvertently releasing transformed seed.

In the exploratory experiment, local stem borers will be offered a "free lunch" of the leaves under tightly controlled conditions to determine the effectiveness of various Bt gene constructs against the pests. CIMMYT entomologist David Bergvinson is overseeing the bioassay work, which will help guide the development of resistance genes in the CIMMYT biotech lab in Mexico.

Meeting Kenya's Needs

At the heart of the project is the development of integrated pest management strategies and superior host plant resistance. Conventional and novel sources of resistance are being sought, including resistance based on Bt genes.

Bt, a naturally occurring soil bacterium, produces proteins that are lethal to many borers. There are no known negative effects on human or animal health, and organic farmers in many parts of the world use Bt in spray form. Because its main action is specific to the larvae of moth species that feed on maize, its impact on non-target insects is thought to be considerably less than the effects of wide-spectrum chemical insecticides.

Cell biologist Natasha Bohorova and her CIMMYT team have inserted synthetic versions of several Bt genes into tropical maize. Cry1B and cry1Ac genes were transformed into a tropical maize background. This maize resists southwestern corn borer (SWCB), sugarcane borer (SCB), and fall armyworm (FAW). A synthetic cry1E gene and a translational fusion cry1B-1Ab gene were also introduced into tropical maize and have shown resistance to FAW, SWCB, and SCB.

Because insect populations evolve to withstand conventional and transgenic pesticides, measures must be taken to extend maize plant resistance. The IRMA approach is to "stack" or "pyramid" a number of Bt genes together with conventional resistance mechanisms to make it that much harder for stem borers to evolve an effective response. In addition, management strategies such as refugia are being studied to help thwart the emergence of Bt resistance.

Researchers will identify and develop gene constructs that contain no herbicide or antibiotic markers. Maize varieties produced by the IRMA Project will carry only "clean" or "purified" Bt genes, circumventing concerns about unforeseen impacts on the environment or human health. While this approach costs more and takes longer, IRMA researchers are committed to addressing all reasonable issues that emerge regarding this technology.

Meanwhile, Mugo and his KARI counterparts are busy identifying the maize that will carry the novel resistance genes. They are looking at numerous elite open-pollinated varieties, inbred lines, and hybrids from CIMMYT, KARI, the Africa Maize Stress Project, and the private sector. They seek plants with traits such as drought escape/tolerance; tolerance of low nitrogen; resistance to Striga, turcicum leaf blight, and gray leaf spot; high yields; and a basic level of stem borer resistance.

Full Steam Ahead

"KARI and CIMMYT are taking this on full steam and are totally committed," says David Hoisington, director of the CIMMYT Applied Biotechnology Center and the IRMA Project. Looking forward to next year, Hoisington affirms that CIMMYT plans to finish inserting all the individual genes of interest into a general maize background. The timeline also calls for completing a biosafety greenhouse in 2001, which will allow IRMA breeders to begin moving the resistance genes into Kenyan maize.

"The first time through these steps is always tough," Hoisington concedes. "But hurdle by hurdle, we're moving towards testing the project's first varieties and ultimately towards seeing Kenyan maize farmers produce more for everyone."

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Published on October 2000

August, 2004

Annual Report 99-2000