Amazing maize

maize_100Research on maize improvement by IITA and partners, including CIMMYT, shows increased harvests and enhanced livelihoods of farmer-beneficiaries in sub-Saharan Africa. Total net benefit from maize research in West Central Africa from 1981 to 2005 alone using varieties from IITA, CIMMYT, and national programs is estimated at US$6.8 billion.

Issue 10, March 2013


Breakthroughs in maize breeding
Extra early white maize hybrids
Ensuring the safety of African crops
Helping farmers benefit from drought tolerant maize
New maize brings hope
Promoting drought tolerant maize
Saving maize from Striga
Ecofriendly bioherbicide
Developing aflasafeTM
Drought tolerant maize for Mali

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Developing aflasafeTM

Joseph Atehnkeng, j.atehnkeng@cgiar.org, Joao Augusto, Peter J. Cotty, and Ranajit Bandyopadhyay

Aflatoxins are secondary metabolites mainly produced by fungi known as Aspergillus flavus, A. parasiticus, and A. nomius. They are particularly important because of their effects on human health and agricultural trade. Aflatoxins cause liver cancer, suppress the immune system, and retard growth and development of children. Aflatoxin-contaminated feed and food causes a decrease in productivity in humans and animals and sometimes death. Maize and groundnut are particularly susceptible to aflatoxin accumulation, but other crops such as oilseeds, cassava, yam, rice, among others, can be affected as well. Aflatoxin accumulation in crops can lower income of farmers as they may not sell or negotiate better prices for their produce. Because of the high occurrence of aflatoxin in crops, many countries have set standards for acceptable aflatoxin limits in products that are meant for human and animal consumption.

Natural populations of A. flavus consist of toxigenic strains that produce variable amounts of aflatoxin and atoxigenic strains that lack the capability to produce aflatoxin. Carefully selected and widely distributed atoxigenic strains are applied on soil during crop growth to outcompete and exclude toxigenic strains from colonizing the crop. The biocontrol technology has been used extensively in the USA with two products AF36 and afla guard® available commercially. In Africa, aflasafeTM was first developed by IITA in partnership with the United States Department of Agriculture – Agricultural Research Service (USDA-ARS) and the African Agriculture Technology Foundation (AATF). It is currently at different stages of development, adoption, and commercialization in at least nine African countries. Multiyear efficacy trials in farmers’ fields in Nigeria have showed reduced aflatoxin concentration by more than 80%.

Survey to collect and dispatch samples
Product development begins with the collection of crop samples in farmers’ stores across different agroecological zones in each country. Samples collected are mainly maize and groundnut because they are the most susceptible to aflatoxin accumulation at crop maturity, during processing, and storage. Soil samples are collected from fields where these crops were grown to determine the relationship between the Aspergillus composition in the soil and the relative aflatoxin concentration in the crop at maturity.

Import and export permits are required if crop and soil samples are shipped outside a country. The crop samples are analyzed for aflatoxin to obtain baseline information on aflatoxin levels in the region/country and the relative exposure of the population to unacceptable limits of aflatoxin.

Isolation and characterization of Aspergillus species
Aspergillus species are isolated from the crop samples to identify the non-aflatoxin-producing species of A. flavus for further characterization as biocontrol agents. The isolates are identified and grouped into L-strains of A. flavus, SBG, A. parasiticus, and further characterized for their ability to produce aflatoxin by growing them on aflatoxin-free maize grain. Aflatoxin is extracted from the colonized grain using standard protocols to determine isolates that produce aflatoxin (toxigenic) and those that do not produce aflatoxin (atoxigenic). The amount of aflatoxin produced by toxigenic strains is usually quantified to determine the most toxigenic strains that will be useful for competition with atoxigenic strains.

Understanding genetic and molecular diversity
The genetic diversity of the atoxigenic strains is also determined molecularly by examining the presence or absence of the genes responsible for aflatoxin production in each strain. The absence of these genes explains why potential biocontrol isolates would not produce aflatoxin after release into the environment. Amplification of any given marker is taken to mean that the area around that marker is relatively intact, although substitutions and small indels outside the primer binding site may not be detected. Non-amplification could result from deletion of that area, an insertion between the primers that would result in a product too long to amplify by polymerase chain reaction (PCR), or mutations in the priming sites. Non-amplification of adjacent markers is probably best explained by very large deletions.

Identification of vegetative compatible groups
Vegetative compatible group (VCG) is a technique used to determine whether the highly competitive atoxigenic isolates are genetically related to each other. In nature A. flavus species that are genetically related belong to the same VCG or family; those that do not exchange genetic material belong to different VCGs. This is an important criterion for selecting a good biocontrol agent to ensure that the selected biocontrol strains do not “intermate” with aflatoxin-producing strains after field application. With this technique, the distribution of a particular VCG within a country or region is also determined. A VCG that is widely distributed is likely to be a good biocontrol agent because it has the innate ability to survive over years and across different agroecologies. On the contrary, atoxigenic VCGs that have aflatoxin-producing members within the VCG are rejected; atoxigenic VCGs that are restricted to a few locations may also not be selected.

Initial selection of competitive atoxigenic strains
The in-vitro test determines the competitive ability of the atoxigenic isolate to exclude the toxigenic isolate on the same substrate. The competition test is conducted in the laboratory by co-inoculating the most toxigenic isolate with atoxigenic strains on aflatoxin-free maize grains or groundnut kernels. Grains/kernels inoculated with the toxigenic strain or not inoculated at all serve as controls. After incubation and aflatoxin analysis, atoxigenic isolates that reduce aflatoxin by more than 80% in the co-inoculated treatments are selected for unique vegetative compatible grouping.

Selection of candidate atoxigenic strains and multiplication of inocula
aflasafe™ is composed of a mixture of four atoxigenic strains of A. flavus previously selected from crop samples. To select the four aflasafe strains, initially 8-12 elite strains belonging to atoxigenic VCGs are evaluated in large farmers’ fields. Two or three strain mixtures, each with 4-5 elite strains, are released in separate fields by broadcasting at the rate of 10 kg/ha in maize and groundnut at about 30-40 days after planting. The atoxigenic strains colonize organic matter and other plant residues in the soil in place of the aflatoxin-producing strains. Spores of the atoxigenic strains are carried by air and insects from the soil surface to the crop thereby displacing the aflatoxin-producing strains. The four best strains to constitute aflasafeTM are selected based on their ability to exclude and outcompete the toxin-producing isolates in the soil and grain, move from the soil to colonize the maize grains or groundnut kernels in the field, and occur widely and survive longer in the soil across many agroecological zones. The use of strain mixture in aflasafe™ is likely to enhance the stability of the product as more effective atoxigenic strains replace the less effective ones in specific environments. The long-term effect is the replacement of the toxigenic strains with the atoxigenic VCGs over years.

Assessing relative efficacy of aflasafeâ„¢
Field deployment to test efficacy of aflasafeâ„¢ is carried out in collaboration with national partners and most often with the extension services of the Ministry of Agriculture. Awareness is created by organizing seminars with extension agents and farmers. During the meetings presentations are made on the implication of aflatoxin on health and trade thereby increasing their knowledge on the impact of aflatoxins. aflasafeâ„¢ is then introduced as a product that prevents contamination and protects the grains before they are harvested and during storage. Efficacy trials are carried out in fields of farmers who voluntarily agree to test the product. Field demonstrations on the use of aflasafeTM are supervised and managed by the extension agents and farmers. Farmers are trained not only on the biocontrol technology but also on other management practices that enhance better crop quality.

Farmers are also educated on the need to group themselves into cooperatives, aggregate the aflasafeâ„¢-treated grains to find a premium market with companies that value good quality products. Market linkage seminars and workshops are organized between aflasafeâ„¢ farmers, poultry farmers, and the industries to ensure that the farmers get a premium for producing good quality grains and the industries get value for using good quality raw materials for their products.

Drought tolerant maize is good for farmers and business in Mali

Vincent Defait, v.defait@gmail.com

Excellent outcomes in farmers’ tests of drought tolerant maize in Mali—where rainless spells persistently wilt harvests and hopes—have increased the demand for maize seeds and raised the crop’s appeal.

Finishing his meal, 67-year-old Malian farmer Bakary Touré smiles and looks over his homestead’s courtyard where friends are eating a traditional corn paste. Some children watch; some women wash pots; a goat wanders among scrawny hens; and a donkey’s sporadic braying shakes the dusty afternoon. This is Kolokani, a village in the heart of a town of 7800 homes some 120 km north of Mali’s capital, Bamako.

“In September 2011, I had nothing to eat, so I sold my goats and chickens to feed my family,” says Touré, referring to a particularly poor harvest. As the head of a household of 22 people he was ready to abandon his homestead at the time but, as he says, “…Maize saved me.” On the advice of fellow farmers in a local cooperative in May 2012, Touré bought 20 kg of seeds of Brico, a drought tolerant (DT) variety with yellow kernels. Sown and managed using recommended practices, the US$15 purchase of seeds grew into a 1.6 t harvest that brought food security to Touré and his homestead. “I gave three bags to friends who will pay me back later,” he says, standing in front of his storage room. “With the 13 bags I have, I can feed my family for six months.”

Other Kolokani farmers have profited by producing and selling seeds of the DT varieties. Near a small warehouse that stores grain sacks, Oumar Traoré, president of the cooperative “The Good Seed”, remembers the first trials with the varieties. “We usually grew more groundnut and sorghum,” he says, “but when we learned that this maize was profitable and drought tolerant, we wanted to try it.” He and his peers grew it on small areas the first year but soon expanded their plots. “The following 2 years, I produced 6 t of maize, mainly to sell as seeds,” Traoré says, as his friends nod in agreement. “It brought me 1.5 million FCFA ($2900) and I bought cows and a motorcycle. Today, our main problem is the cost and availability of mineral fertilizer on the market. If we cannot buy enough in a timely manner, we have to cut back the maize area,” says Traoré. Despite this, he says that production of DT maize allows him to easily feed his family with 13 members and sell seeds for as much as $1/kg.

A new movement toward maize
That maize can save the day is surprising news in Kolokani where the yearly rainfall, 600 mm or less, has favored more water-sparing crops, such as sorghum, groundnut, and sesame. But Bakary Touré and Oumar Traoré are among thousands of Malian farmers taking up DT maize varieties.
“Mali is one of the countries in West Africa where maize production has expanded into areas where drought stress occurs intermittently,” says Abebe Menkir, IITA’s Maize Breeder, who works with Mali’s Institute of Rural Economy (IER) to develop DT maize varieties and make them available to farmers. “With these varieties, Mali has the opportunity to expand maize production into areas where it was not possible before because of droughts.”

“In Mali, DT maize could revolutionize the lives of farmers,” says N’Tji Coulibaly, an IER agronomist and head of its maize research program who is testing and promoting the new varieties with farmers. Mali is a landlocked country in West Africa of 15.5 million inhabitants. Less than 4% of the land is arable; 8 of every 10 citizens are engaged in agriculture or fishing around the Niger River. Since the mid-1990s, domestic maize production and consumption have grown significantly, based on the crop’s high yield potential and responsiveness to fertilizer, its capacity to alleviate food deficits, as well as its export potential and value for processing and food industries. “The introduction of DT maize seeds can speed the attainment of the Government’s main objective of food sufficiency for Malian farmers.”

Smallholder farmers earn a surplus by growing seeds
The varieties that Coulibaly and Menkir test and promote are products of the Drought Tolerant Maize for Africa (DTMA) project, implemented since 2006 by IITA and the International Maize and Wheat Improvement Center (CIMMYT), with funding from the Bill & Melinda Gates Foundation, the Howard G. Buffet Foundation, USAID, and the British Department for International Development.
In the IER office in Bamako, Coulibaly traces the beginnings of the DTMA project in Mali. “We worked with farmers to select the best seeds, those that adapt best to areas where drought is endemic,” he says. “From 2009, two early maturing open-pollinated varieties were released that farmers have dubbed Brico, the name of a town in Mali, and Jorobana, which means “no worries” in the Bambara language. In areas where drought can reduce production by 70%, DT maize is a godsend. Ideally, we should introduce one or two new DT varieties each year.”

IER also helps to teach farmers the skills and know-how to produce certified seeds. Among other things, this requires them to follow a schedule for applying fertilizer, weeding the plots, and maintaining enough separation between maize crops to avoid cross-pollination.

Best and timely practices
Coulibaly describes a series of marketing challenges that need to be addressed. “We must find a way to produce more basic seeds,” he says, referring to the seeds that are multiplied by companies and other commercial seed producers. “In particular, it is often necessary (for someone) to quickly buy the seeds the farmers produce because without money (from those sales), they have nothing to eat; they cannot wait for a potential buyer to knock on their door.” Coulibaly adds that, by the same token, farmers are not able to plan well for their own needs over the medium term. “In general, when a drought is looming, they all want DT seeds at the same time.”

These considerations do not seem to have reached Tanabougou, a village where only the minaret of the tiny mosque stands over the lot of concessions. The capital is only 40 miles away, but to get there one first needs to reach the paved road along a track on which only a few vehicles raise clouds of sand. Run down and often closed businesses in the city of Koulikoro, the capital of the eponymous region, give the impression that there has never been any impact on life in the villages. The Niger River is close, but it seems to belong to another world. In Tanabougou, it is the rain that supplies water to the crops. Animals, mainly goats and donkeys, crop the residues of harvest and the few tufts of grass under the trees.

In his banco concession where bright yellow maize cobs dry on a nga, a wooden roof and branches, another farmer, Benkeba Traoré, 56, says, “With traditional maize varieties, I was producing about 300 kg per year. Last year, with the drought tolerant variety Brico, I produced 2 t of maize and sold 800 kg as seeds to Faso Kaba, a seed business owned by a woman entrepreneur.” In two seasons Benkeba Traoré, who has to feed four adults and 12 children from 3.5 ha, was able to buy a pair of oxen and a plow, “Soon,” he says, “I will replace the branches which surround the concession with corrugated iron.”

The progress was also made possible by the training provided by the agronomists of IER and the technicians of Faso Kaba. For the past 3 years, the farmer has learned to isolate his seed production from other plots, to meet deadlines when spreading fertilizer, to recognize the quality of the soil, and to sow suitable seed varieties.

Rotating crops
When asked if he was not tempted to abandon the other crops, given the high yield of DT maize and the money it generates, farmer Traoré replies, “Last year, I reduced the area of sorghum and groundnut in favor of maize. Sorghum was a failure and maize saved me. But next year, it may be the other way round, so I prefer to continue to grow more cereal crops.”

The farmer now hopes to marry off his two oldest children and buy a motorcycle (about 300,000 FCFA or US$580) to travel to the village. “Today, I have no problems with the soudure,” Traore insists. All farmers in West Africa know about this difficult time between the end of the stock and the next harvest.

Lassana Diakite, 64, is reassured too. He chairs the cooperative from Koula, a neighboring village at the center of a little town with 25,000 inhabitants, several hours walk from the marketplace. Sitting on a wooden bench in the shade of a tree overlooking his concession, the farmer describes in a serious voice the various stages of maize cropping. “From plowing to sowing and harvesting, each step is recorded. I know when I need to weed, when I have to spread fertilizer, when I have to harvest … I even know my yields in advance. ” That is a lot of advantages for this head of a family of 35 people who inhabit parts of the banco concession.

In the first year, the farmer used 1.5 of his 12 ha for production of Jorobana seeds. The result: 1.7 t of maize harvested. Three years later, production has climbed to 4.6 t. “Drought tolerant maize beats conventional maize as the horse beats the donkey,” asserts the farmer.

The next tcheba seeds…
Looking at the nga, where the sun shines on his maize spread like gold nuggets, the farmer adds, “Next year I will sow 3 or 4 ha.” It is impossible for him to devote all his 12 ha to maize. “I do not have the labor,” he continues. “I would have to stagger the fields and interventions and that would compromise performance.”

Diakité acknowledges his new comforts, the oxen he recently acquired, the taxes he pays “with ease,” the education of his children, which is now more affordable, and the fertilizer for the sorghum that he can buy with the money generated by maize.

Back in Bamako, in his office at IER, Coulibaly dreams of the next generation of DT maize varieties. His team has just completed tests on hybrid varieties which are more productive. In 2013, Malian farmers should be able to grow the Tcheba variety meaning ‘big’ in Bambara. The agronomist said, “In Mali, with DT maize, we can speak of a success story…

Tanzanian president inaugurates new science building

The President of the United Republic of Tanzania, His Excellency, Dr Mrisho Jakaya Kikwete, in May, inaugurated IITA’s new science building in Dar es Salaam, Tanzania.

The construction of the science building represents an investment of over US$4 million and is part of IITA’s efforts to strengthen its research capacity and that of its partners in sub-Saharan Africa.

“The science building is a symbol of IITA’s commitment to continue waging the fight against hunger and poverty and boost agriculture through capacity development and improve the livelihoods of smallholder farmers in East Africa through its research-for-development efforts,” says Dr Nteranya Sanginga, IITA Director General.

Citing IITA for its R4D work in http://pangeagiving.org/cheap/ sub-Saharan Africa, President Kikwete lauded the construction of the science building, saying that any effective socioeconomic transformation which would have levitra online cheap a significant impact on poverty reduction in Tanzania and Africa should be anchored on agriculture.

The inauguration was followed by a tour of the new building and exhibition booths showcasing IITA’s work in East Africa, and a workshop with the theme “Grow Africa and the role of agricultural research by national systems, IITA, and its partners.”

The state-of-the-art and environmentally friendly Science Building has five modern laboratories with a capacity to host 70 researchers.

Nigeria releases improved cassava varieties

Nigeria has released two new improved cassava varieties developed through a collaborative effort between IITA and the Nigerian Root Crops Research Institute (NRCRI), Umudike. The two varieties are originally recognized as IITA-developed genotypes IITA-TMS-I982132 and IITA-TMS-I011206, now known as UMUCASS 42 and UMUCASS 43, respectively.

Both varieties performed well in different cassava production regions of Nigeria with high yield, high dry matter, and good disease resistance. The roots of these varieties are yellow and contain moderate levels of provitamin A.

The potential maximum yield of the two varieties is between 49 and 53 t/ha, according to pre-varietal release trials that were conducted between 2008 and 2010. Local varieties produce less than 10 t/ha. The varieties are also resistant to major pests and diseases that affect cassava in the country including cassava mosaic disease, cassava bacterial blight, cassava anthracnose, cassava mealybug, and cassava green mite.

The varieties are good for high quality cassava flour—a trait sought after by researchers for the cassava transformation agenda in Nigeria; have high dry matter which is positively related to starch and important for cassava value chain development; have high leaf retention which is positively related to drought tolerance and is crucial for cassava production in the drier regions and in mitigating the impact of climate change, with moderate levels of betacarotene for enhancing nutrition.

Cassava project launches database

Cassavabase, a database that promotes open access data sharing, was launched recently.

IITA is a major contributor of data to www.cassavabase.org and will host this information resource through the NEXTGEN Cassava project.

Cassavabase features phenotypic and genotypic data generated by cassava breeding programs involved in the NEXTGEN Cassava project at Cornell University supported by a US$25.2 million grant from the Bill & Melinda Gates Foundation and the Department for International Development of the United Kingdom.

The database makes the data immediately and openly accessible to the whole cassava community prior to publication. It is being developed by Lukas Mueller, adjunct professor of plant breeding and genetics at Cornell, at the Boyce Thompson Institute in Ithaca, New York.

Cassavabase provides a “one-stop shop” for cassava researchers and breeders worldwide. In addition to phenotypic and genotypic data, Cassavabase offers access to all genomic selection analysis tools and phenotyping tools developed by the NEXTGEN Cassava project, and links to auxiliary genome browsers, ontology tools and social networking tools, for the cassava community.

Biocontrol product reduces mortality in poultry

A study by scientists from IITA and the University of Ibadan, Nigeria, has found that poultry fed with maize treated with aflasafeâ„¢ experienced reduced mortality in addition to other benefits.

Results from the feeding experiment involving 1,020 broilers showed that the use of maize from aflasafeâ„¢-treated feeds reduced mortality rate by 43.9%, feed intake dropped by 10.4%, and there was an increase of 3.3% in feed conversion ratio.

The results show the impact of aflasafe™—a biological control product developed by IITA for controlling aflatoxins.

Produced by toxigenic strains of Aspergillus flavus, aflatoxins have become a menace in developing countries, contaminating about 25% of grains produced in the region. The aftermath effects of consuming aflatoxin-contaminated grains include stunting in children, liver cancer, and even death.

Ecofriendly bioherbicide approach for Striga control

Abuelgasim Elzein, a.elzein@cgiar.org, and Fen Beed

Root parasitic weeds of the genus Striga are a significant constraint to cereal and cowpea production in sub-Saharan Africa. They can cause total crop losses particularly during drought, in infertile soils and cereal monocropping. Striga causes annual losses of US$7 billion and affects incomes, food security, and nourishment of over 100 million people mostly in sub-Saharan Africa.

Each Striga plant can produce thousands of seeds, viable for over 10 years. Their intimate interaction with different host plants prevents the development of a silver bullet control technology that subsistence farmers can adopt. Hence, it is widely accepted that an integrated approach to Striga management is required for which biocontrol represents a crucial component.

Bioherbicide innovation
A bioherbicide is a plant pathogen used as a weed biocontrol agent (BCA), which is applied at sufficient rates to rapidly cause a disease epidemic that kills or severely suppresses the target weed. The use of biocontrol technology to manage Striga is a desirable control method as it is environmentally friendly, safe to farmers and crop consumers, specific to the target host, and has the potential to be economically viable. In addition, biological control also assists in the development of a balance of nature, the creation of more biodiversity, and sustaining of complex ecological interactions.

Since the early 1990s, a series of intensive disease surveys in many countries of sub-Saharan Africa has evaluated hundreds of microorganisms for their pathogenicity and virulence against Striga. Fusarium oxysporum Schlecht isolates have been the most promising. However, the discovery of a highly effective pathogen is only one step in the process of developing bioherbicides, for which the inoculum mass production, formulation, delivery, and storage ability must be optimized, and the mode of action, host specificity, and biosafety evaluated and fully understood.

The most widely studied and used fungal isolate that met all requirements for a potential bioherbicide for Striga is F. oxysporum Schlecht f. sp. strigae Elzein et Thines (isolates Foxy2 and PSM197). These are highly virulent, attack Striga in all growth stages—from seed to germination, from seedling to flowering shoot; protect the current crop yield; and prevent seed formation and dispersal.

F. oxysporum f. sp. strigae is highly host-specific to the genus Striga, and does not produce any known mycotoxic compounds. Thus, its use does not pose health risks to farmers, input suppliers, traders or consumers or threaten crops or the environment. Its unique DNA constitution differs from other forms of F. oxysporum deposited in GenBank, known to cause crop diseases. Indeed, this ensures its biosafety and greatly facilitates its wider application and use as a bioherbicide.

In addition techniques for massive production of inoculum of F. oxysporum f. sp. strigae was optimized based on simple and low-cost methods and using inexpensive agricultural by-products available in sub-Saharan Africa. The chlamydospores produced by this fungus have the advantage of being able to survive extreme environmental events while still remaining viable. This is an important feature required for a BCA suited to hot and dry climatic conditions of cereal production in sub-Saharan Africa, and to produce stable, durable, and pathogenic propagules.

Extensive research by the University of Hohenheim (UH, Germany), IITA (Benin), McGill University (Canada), and Institute for Agricultural Research – Ahmadu Bello University (Nigeria), has enhanced application of F. oxysporum f. sp. strigae, its formulation into bioherbicidal products, and its delivery for practical field application. The Striga bioherbicide contains the Striga host-specific F. oxysporum f. sp. strigae, applied in massive doses to create a high infection and disease level to kill or severely suppress Striga.

Promotion in West Africa
The bioherbicide is a component of the IITA-led project, Achieving sustainable Striga control for poor farmers in Africa, funded by the Bill & Melinda Gates Foundation to intensively promote technologies to combat Striga in sub-Saharan Africa. The project will validate the potential of the bioherbicide seed treatment technology across major Striga-infested agroecological zones and maize-based farming systems, while also confirming the biosafety and developing molecular detection tools. Here are the highlights of the results:

Technology validation: Several multilocation trials were conducted under natural and artificial Striga infestation across two agroecological zones in northern Nigeria to evaluate the efficacy of Striga bioherbicide (F. oxysporum f. sp. strigae). The inoculum produced by UH and SUET seed company was delivered as a film-coat on maize seeds (see below).The application of the bioherbicide technology in combination with Striga resistant maize reduced Striga emergence by 73% and 39%, compared to the susceptible and resistant controls, respectively, and prevented 81% and 58% of emerged Striga plants from reaching flowering and 56% and 42% of the maize plants from attack by Striga (see next page). The combination of bioherbicide with Striga susceptible variety significantly reduced Striga emergence by 53%, resulting in 42% reduction in number of flowering plants and in 21% increase in grain yield compared to the susceptible control.

In addition, disease symptoms were recorded on emerged Striga plants parasitizing maize plants coated by the bioherbicide. The reduction in Striga emergence across maize varieties indicates the effectiveness of the bioherbicide to attack seeds under the soil surface. The synergistic effect of the bioherbicide technology combined with the Striga resistant maize is expected to reduce the Striga seedbank and thus the impact of Striga on subsequent maize crops.

Biosafety: To further ensure the safety of Striga BCA and to demonstrate and increase awareness among farmers, regulatory authorities, and stakeholders, a wide host range study was carried out using 25 crops in collaboration with IAR-ABU and the Nigerian Plant Quarantine Service (NPQS)  under field and screenhouse conditions in Nigeria. Results revealed that none of the test plants showed any infection by the biocontrol agent both in the field and screenhouse, and no detrimental growth effects were measured or visual losses to plant health recorded in any of the inoculated crops tested, i.e., inoculation with the Striga BCA did not cause any delay in emergence, and a decrease in plant height, plant vigor, chlorophyll content per leaf, shoot fresh and dry weight. Hence, the Nigerian regulatory authorities (NPQS, NAFDAC) and other stakeholders were satisfied and confident that no disease was produced on plants other than Striga by the BCAs and that it is safe to use. In addition, a mycotoxin produced by Striga bioherbicide  F. oxysporum f. sp. strigae was analyzed and evaluated by our project partner, the University of Stellenbosch in South Africa. An evaluation of existing isolates of F. oxysporum f. sp. strigae does not produce well-known mycotoxins (e.g., Fumonisin and Moniliformin) that pose a threat to animal or human health. This finding further confirms the safety of this bioherbicide.

Molecular detection tools: Development of a monitoring tool specific to the Striga bioherbicide is important to certify inoculum quality, monitor the presence and persistence of the BCA in soils, and validate its environmental biosafety. UH is developing a monitoring tool.

The AFLP fingerprinting technique was successfully used in developing a primer pair capable of differentiating the F. oxysporum f. sp. strigae group from other Fusarium species. In addition, the monitoring tool has shown a high specificity for isolate Foxy2 and was used to monitor its spread and persistence in rhizobox experiments under different management practices using Kenyan soils. This promising result provides a proper baseline to further the existing primer set.

Bioherbicide + pesticide technology: The novel combination and integration of the bioherbicide technology plus imazapyr herbicide for Striga control with pesticides in a single-dose seed treatment to control fungal pests offers farmers with maize seed that is able to achieve its yield potential. The use of each technology (BCA or imazapyr) has been shown to be effective when applied independently using seed coating techniques, but have not been integrated.

The compatibility of Striga BCAs with different pesticides (herbicides and fungicides with insecticide components) was studied in vitro in the laboratory. Striga BCAs showed excellent compatibility with imazapyr (a herbicide seed coating used in combination with IR maize to control Striga), Metsulfuron Methyl (MSM) (a herbicide seed coating developed by DuPont to control Striga in sorghum), and glyphosate (an intensively used herbicide). A similar result was also achieved with the commonly used seed treatment fungicides at the recommended application doses.

Accordingly, doses and complementary seed coating protocols for the three compatible technologies (BCA, herbicide, and fungicides) have been developed and IR maize seeds were successfully coated with a single-dose seed treatment of BCA inoculums and imazapyr. The results showed that imazapyr did not interfere with the BCA during seed coating, with BCA growth and sporulation after coating, and with IR maize seed germination. Seeds of IR maize varieties can thus be coated with the herbicide and the BCA and then fungicide and delivered to farmers using the same input pathway. Screenhouse and field trials are being carried out to generate data on the combined efficacy of the applied technologies. The demonstrated compatibility of Striga BCA with the different pesticides that contain a wide range of active ingredients indicate that the combination and delivery of the Striga bioherbicide technology with a large number of pesticide products is possible. These findings are expected to provide a triple action seed coating package for direct control of Striga and fungal diseases of maize in sub-Saharan Africa.

Suitability to African farming systems
Our strategy for scaling-up the bioherbicide innovation is based on using technology appropriate to Africa to ensure that sustained production of the bioherbicide is feasible at a cost affordable to African small-scale farmers. The seed-coating treatment requires significantly less inoculums, establishes the BCA in the cereal rhizosphere, i.e., the infection site of Striga, and provides a simple, practical, cost-effective delivery system for adoption by input suppliers to subsistence farmers. Arabic gum as a coating material has been shown to increase the rate of mycelia development and enhance BCA sporulation. Its availability in sub-Saharan Africa at a low price is an additional economic advantage. A commercial seed coating process, developed and optimized at UH with SUET Seed Company in Germany, is being transferred and adapted at IITA, Ibadan, to be used as an experimental production unit for capacity building and as a model for eventual transfer of seed treatment technology to the private sector after validation.

Outlook
One unique advantage of this bioherbicide is that the ability of Striga to become resistant to it is virtually unknown as a consequence of the suite of enzymes and secondary metabolites that the BCA produce to become pathogenic and virulent against the target (Striga). Hence after validation, delivering the bioherbicide technology in combination with resistant maize or with the herbicide imazapyr is expected to increase efficacy in controlling Striga. Bioherbicide and other compatible technologies have different modes and sites of action against Striga, and in a combination they will have a much greater chance of reducing the potential risk of development of resistance to a single technology (resistant varieties or herbicides) used separately and repeatedly.
The potential delivery of coated seeds of resistant maize with bioherbicide in one package to farmers using the same input pathway will reduce transaction and application costs and enhances the economic feasibility and adoptability of the technologies. Similarly, compatibility of BCA with imazapyr and fungicides allow seed coating of IR-maize with bioherbicide, imazapyr, and fungicides with a single-dose seed coating application.

Future plans
Currently, large-scale field testing is ongoing and is being implemented to further validate bioherbicidal efficacy across two agroecological zones where the common scenarios for maize infestation by Striga in northern Nigeria are represented. For understanding of farmers’ preferences and perceptions, socioeconomic analysis and cost-benefit analysis of bioherbicidal technology based on field data/surveys and interviews, current market information, and links with other Striga control strategies will be undertaken. After validation, dissemination and commercialization will be promoted through private sector partnerships and integrated with other control options such as resistant varieties, IR varieties combined with seed treatment with imazapayr, crop rotation with legumes, and soil fertility management practices, to achieve sustainable management of Striga.

Partners
IITA (Dr F. Beed, Dr A. Elzein & Dr A. Menkir), Institute for Agricultural Research – Ahmadu Bello University (Dr A. Zarafi), Nigeria; University of Hohenheim (Prof G. Cadisch, Dr F. Rasche & Prof J. Kroschel), Germany; The Real-IPM Company Ltd (Dr H. Wainwright), Kenya; University of Stellenbosch (Prof A. Vilioen), South Africa; and McGill University (Prof A. Watson), Canada.

References
Beed F.D., S.G. Hallet, J. Venne, and A. Watson. 2007. Biocontrol using Fusarium oxysporum; a Critical Component of Integrated Striga Management. Chapter 21 in Integrating New Technologies for Striga control: Towards ending the Witch-hunt (Ejeta, G. and J. Gressel, eds). World Scientific Publishing Co. Pte. Ltd. pp 283-301.

Ciotola, M., A. DiTommaso, and A. Watson. 2000. Chlamydospore production, inoculation methods and pathogenicity of Fusarium oxysporum M12-4A, a biocontrol for Striga hermonthica. Biocontrol Science and Technology 10: 129-145.

Ejeta, G. 2007. The Striga scourge in Africa: A growing pandemic In: Ejeta, G. and J. Gressel, eds. Integrating New Technology for Striga Control: Towards Ending the Witchhunt. World Scientific Publishing Co. Pte. Ltd., UK. pp. 3-16.

Elzein, A.E.M. 2003. Development of a granular mycoherbicidal formulation of Fusarium oxysporum “Foxy 2” for the biological control of Striga hermonthica. In: “Tropical Agriculture 12– Advances in Crop Research (2)” (J. Kroschel, ed.). Margraf Verlag, Weikersheim, Germany, 190 pp, ISBN 3-8236-1405-3.

Elzein, A., J. Kroschel, and V. Leth. 2006. Seed treatment technology: an attractive delivery system for controlling root parasitic weed Striga with mycoherbicide. Biocontrol Science and Technology, 16(1) 3-26.

Elzein, A., F. Beed, and J. Kroschel. 2012. Mycoherbicide: innovative approach to Striga management. SP-IPM Technical Innovations Brief, No. 16, March 2012.

Kroschel, J. and D. Müller-Stöver. 2004. Biological control of root parasitic weeds with plant pathogens. In: Inderjit, K. (ed.), Weed biology and management. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 423–438.

Kroschel, J., A. Hundt, A.A. Abbasher, J. Sauerborn. 1996. Pathogenicity of fungi collected in northern Ghana to Striga hermonthica. Weed Research 36 (6), 515–520.

Marley, P.S., S.M. Ahmed, J.A.Y. Shebayan, and S.T.O. Lagoke. 1999. Isolation of Fusarium oxysporum with potential for biocontrol of the witchweed Striga hermonthica in the Nigerian Savanna. Biocontrol Science and Technology 9: 159–163.

Venne J., F. Beed, A. Avocanh, and A. Watson. 2009. Integrating Fusarium oxysporum f. sp. strigae into cereal cropping systems in Africa. Pest Management Science 65: 572–580.

Breakthroughs in maize breeding

B. Badu-Apraku, b.badu-apraku@cgiar.org, M. Oyekunle, and R.O. Akinwale

Extra-early maize inbreds and hybrids that are resistant to Striga, tolerant of low nitrogen (N) and drought at flowering and grain filling periods, and that combine tolerance for these three stresses are now available in sub-Saharan Africa as a result of the painstaking research under the Maize Improvement Program at IITA.

Maize is the most important cereal crop after rice in West and Central Africa. However, during the last two decades, its production and productivity have lagged behind population growth for several reasons. These include low soil fertility, little or no use of improved seeds, herbicides, and fertilizers, inadequate plant density, weed infestation, poor tillage practices, labor shortages, increased levels of biotic and abiotic constraints, and high costs of inputs. In addition, serious infrastructural and institutional constraints have limited the adoption of improved maize technologies. Climate change and its associated effects have also resulted in altered weather patterns leading to erratic and unreliable amounts and distribution of rainfall, resulting in drought. Presently, stresses from Striga infestation, drought, and low N are the most important biotic and abiotic factors that limit maize production in the region.

Four maturity groups are needed to satisfy the maize varietal requirements of the subregion for human consumption, poultry and livestock feed, and industrial use. These groups are the extra-early varieties (80-85 days to maturity), early (90-95 days to maturity), intermediate (100-110 days to maturity), and late (>120 days to maturity). Extra-early varieties play a unique role in filling the hunger gap in July in the Sudan savanna and the northern Guinea savanna zones after the long dry season. The extra-early varieties are also used for late planting when the rains are delayed, for intercropping with cassava, millet, and sorghum, and as “green maize” in the forest agroecology where they allow early access to the market for a premium price. The availability of early and extra-early varieties has significantly contributed to the expansion of maize to new frontiers in the savanna agroecology, replacing sorghum and millet.

A major strategy of IITA’s Maize Improvement Program is to breed cultivars that are Striga resistant and drought- and low-N tolerant to increase and stabilize maize yield production in the subregion. Two approaches have been adopted for drought tolerance. The first is to breed for extra-early maturing cultivars that are drought escaping. These cultivars are adapted to drought-prone environments in West and Central Africa; they mature and complete their life cycles before severe moisture deficit occurs or before the onset of terminal drought. The second strategy is to breed drought-tolerant cultivars with better adaptation to drought-prone environments under induced drought stress. This is achieved by introgressing or introducing into extra-early cultivars the genes for drought tolerance to enable them to withstand mid-season drought when it occurs during the flowering and grain-filling periods.

Breeding for adaptation to drought-prone environments
The goal of the IITA Maize Program is to develop open-pollinated and hybrid maize cultivars adapted to the different forms of climatic variation prevalent in West and Central Africa with emphasis on drought stress. The naturally available mechanisms for drought escape and drought tolerance in the germplasm and the prevailing production environments in West and Central Africa were exploited to develop cultivars with enhanced adaptation to stressful environments. Drought escape occurs when the plant completes critical physiological processes before drought sets in. This trait is quite desirable in cultivars to be released to farmers in areas where terminal drought is most prevalent. Adaptation to drought-prone environments, on the other hand, is under genetic control and indicates the presence of physiological mechanisms that minimize or withstand the adverse effects of drought if and when it occurs. Cultivars with enhanced adaptation to drought-prone environments are useful where drought occurs randomly and at any growth stage of the maize crop. This is quite relevant in West and Central Africa where drought occurrence is erratic, with varying timing and levels of intensity.

Using the two strategies, IITA has, during the last two decades, developed a wide range of high-yielding drought tolerant or drought-escaping extra-early Striga resistant populations (white and yellow endosperm), inbred lines, and cultivars to combat the threat posed by the weed Striga hermonthica and recurrent drought in the savannas of West and Central Africa. The extra-early populations from which the inbred lines and cultivars were derived were formed from crosses between local landraces, exotic, and introduced germplasm identified through extensive multilocation trials in West and Central Africa. They were selected based on high grain yield, earliness, and resistance to the maize streak virus (MSV), and above all on adaptation to the high temperatures and drought stress characteristic of the Sudan savanna in Burkina Faso, Mali, Mauritania, Ghana, Nigeria, and Niger.

The extra-early germplasm was expected to have adaptive traits for tolerance to these stresses in the environments where the cultivars had survived. Some of the extra-early inbred lines in the IITA Maize Program not only escaped drought stress but also seemed to possess drought tolerance genes. The inbreds, early, intermediate, and late-maturing, are also able to withstand the mid-season drought that occurs during the flowering and grain filling periods in the savannas of West and Central Africa.

Selection for tolerance for drought under managed drought stress
Selection for extra-earliness in the IITA Maize Program has been carried out in the savannas of the subregion. So far, several cultivars have been bred, some of which have been released to farmers after extensive testing in the different countries in the subregion.

Induced drought stress for selection for drought tolerance in extra-early maize is achieved by withdrawing irrigation water from 21 days after planting until maturity, with the plants relying on water stored in the soil for growth and development. Promising inbred lines selected for drought tolerance were used to develop extra-early maturing open-pollinated and hybrid cultivars with enhanced adaptation to drought-prone environments. The selected lines are also used as sources of tolerance genes for introgression into extra-early breeding populations that are undergoing recurrent selection. Using this strategy, several extra-early drought tolerant and Striga resistant cultivars with enhanced adaptation to drought-prone environments have been bred.

Selection for tolerance for low soil N
In most developing countries, maize production is carried out under conditions of low soil fertility which further compounds the problems of drought stress and Striga infestation on productivity. Estimated yield losses from N-stress alone can be as high as 50% (Wolfe et al. 1988). Therefore, the development and adoption of maize germplasm with tolerance for multiple stresses are crucial for increased productivity. Banziger et al. (1999) showed that improvement for drought tolerance also resulted in specific adaptation and improved performance under low-N conditions, suggesting that tolerance to either stress involves a common adaptive mechanism.

Identification of inbreds and hybrids with genes for tolerance for low soil N and drought
Three experiments were conducted between 2007 and 2010 in Nigeria to identify extra-early inbreds with tolerance for low N and/or drought stress at flowering and grain-filling periods, and to determine the potential of the inbreds for hybrid production and as a source of germplasm for improving breeding populations. In the first two experiments, 90 extra-early maturing maize inbred lines were evaluated in Nigeria at Ikenne (6º 53’N, 3º 42’E, 60 m altitude, 1200 mm annual rainfall) under managed drought stress and in well-watered environments during the dry seasons of 2007/2008 and 2008/2009. Similarly, the lines were evaluated in low-N (30 kg/ha) and high-N (90 kg/ha) studies at Mokwa (9º 18’N, 5º 4’E, 457 m altitude, 1100 mm annual rainfall) during the growing seasons of 2008 and 2009.

Results identified several stable and high-yielding hybrids ideal for drought environments and pinpointed the fact that the extra-early inbreds and hybrids are not only drought-escaping but also possess genes conferring drought and/or low-N tolerance. TZEEI 6, TZEEI 4, TZEEI 36, and TZEEI 38 were identified as ideal inbreds under drought. Under low N, TZEEI 19, TZEEI 96, and TZEEI 45 were top ranking with TZEEI 19 the ideal inbred. TZEEI 19, TZEEI 29, TZEEI 56, TZEEI 38, and TZEEI 79 were tolerant to both stresses. Eighteen of the 36 hybrids produced above-average yields across environments with four hybrids identified as very stable. TZEEI 29 × TZEEI 21 was the closest to the ideal genotype because it combined large mean performance with high yield stability.

Badu-Apraku et al. (2013) evaluated 17 of the 90 extra-early white maize inbreds tolerant to drought and low-N used in the earlier studies under drought, Striga, and in optimal environments at three locations in Nigeria for 2 years. Results indicated that the test environments were unique and that there were adequate genetic differences among the inbred lines to allow good progress from selection for improvements in the traits and to serve as sources of favorable alleles for improving breeding populations for drought tolerance at the flowering and grain-filling periods and Striga resistance and to serve as parents for developing superior hybrids.

Under drought stress, the mean grain yield of the hybrids ranged from 1114 kg/ha for TZEEI 14 × TZEEI 13 to 2734 kg/ha for TZEEEI 29 × TZEEI 21. The top-ranking hybrid, TZEEI 29 × TZEEI 21, outyielded by 13% the best Striga resistant and drought tolerant early maturing open-pollinated variety, TZE-W DT STR C4. Under well-watered conditions, the top-yielding hybrid was TZEEI 3 × TZEEI 13 (5868 kg/ha) while the lowest was TZEEI 14 × TZEEI 13 (2749 kg/ha). Under artificial Striga infestation, TZEEI 29 × TZEEI 14 was the top ranking hybrid, outyielding by 22% the best Striga and drought tolerant early open pollinated check, TZE-W DT STR QPM.

A stability analysis of the top 20 and worst five single-cross hybrids and four early open pollinated check cultivars revealed TZEEI 29 × TZEEI 14 as the second highest yielding and most stable single-cross hybrid across research environments; the highest-yielding single-cross hybrid, TZEEI 6 × TZEEI 14, was the least stable.

Badu-Apraku and Oyekunle (2012) also conducted two more studies for 2 years at five locations in Nigeria. TZEEI 79 × TZEEI 76 turned out to be the highest yielding and most stable hybrid across environments. It was concluded that the available extra-early yellow maize inbred lines are not only drought-escaping but also possess genes for drought tolerance at flowering and grain-filling periods.

The availability of these Striga resistant, low N and drought-tolerant extra-early inbreds and hybrids should go a long way in reducing the instability of maize yields in sub-Saharan Africa, especially in the savannas and during the second season in the forest ecologies.

References
Badu-Apraku, B. and M. Oyekunle. 2012. Genetic analysis of grain yield and other traits of extra-early yellow maize inbreds and hybrid performance under contrasting environments. Field Crops Research 129: 99–110.
Badu-Apraku., B., M.A.B. Fakorede, M. Oyekunle, and R.O. Akinwale. 2011. Selection of extra-early maize inbreds under low N and drought at flowering and grain-filling for hybrid production. Maydica 56: 29-41.
Badu-Apraku, B., M. Oyekunle, R.O. Akinwale, and M. Aderounmu. 2013. Combining ability and genetic diversity of extra-early white maize inbreds under stress and non-stress environments. Crop Science 53: 9–26.
Badu-Apraku, B., M. Oyekunle, R.O. Akinwale, and A.F. Lum. 2011. Combining ability of early-maturing white maize inbreds under stress and nonstress environments. Agronomy Journal 103: 544-557.
Badu-Apraku, B., M.A.B. Fakorede, A. Menkir, A.Y. Kamara, and A. Adam. 2004. Effects of drought screening methodology on genetic variances and covariances in Pool 16 DT maize population. Journal of Agricultural Science 142: 445-452.
Betran, F.J., J.M. Ribaut, D. Beck, and De Leon D. Gonzalez. 2003. Genetic diversity, Specific combining ability, and heterosis in tropical maize under stress and nonstress environments. Crop Science 43: 797-806.
Bänziger, M., G.O. Edmeades, and H.R. Lafitte. 1999. Selection for drought tolerance increases maize yields across a range of nitrogen levels. Crop Science 39:1035-1040.
Wolfe, D.W., D.W. Henderson, T.C. Hsiao, and A. Alvio. 1988. Interactive water and nitrogen effects on maize. 11. Photosynthetic decline and longevity of individual leaves. Agronomy Journal 80: 865−870.
Yan, W. 2001. GGE Biplot- A windows application for graphical analysis of multi-environment trial data and other types of two-way data. Agronomy Journal 93: 1111-1118.
Yan, W. and J. Frégeau-Reid. 2008. Breeding line selection based on multiple traits. Crop Science 48: 417-423.