Breakthroughs in maize breeding

B. Badu-Apraku,, 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.

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.
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Helping smallholder farmers reap the most from drought tolerant maize

Florence Sipalla,

At the first sign of the short rain season, farmers know that it is time to till the land and plant. In these harsh times, when rain is scarce, some farmers opt to plant before the rain comes to take advantage of every drop. James Mativo from Makaveti Village in Kyanzasu sublocation in Machakos County is one such farmer. He proudly displays a healthy crop to visitors, with green maize ready for plucking. “I planted just before the season began, to ensure that the crop would sprout when the rain came,” he explains.

For many farmers in the semi-arid Eastern Province in Kenya, preparing fields ahead of the rain is not enough to guarantee a good harvest. Having the right seeds is vital too. Mativo buys certified seeds, suited to the area’s climate, from Dryland Seed Company in Machakos town. “For these dryland varieties, the first rains are very important,” explains Peter Mutua, a Dryland agronomist. “It allows the farmers to take full advantage of this scarce resource from germination. This is particularly important as most farmers in Kenya grow maize under rainfed conditions, even in the semi-arid areas.”

Just as a relay race is a team effort, so is the process of delivering quality seeds to farmers. It takes many people, working together, to ensure that farmers get the best seeds suited to the climatic conditions in their locales. Take the case of drought tolerant maize varieties: the process starts with breeders who develop the germplasm and share it with research partners. They pass the baton to the seed companies who produce large quantities of the seeds which smaller-scale farmers buy from them. The companies cross-pollinate sources of desirable traits to develop maize varieties relevant to the farmers. Often they start with sources from public research organizations such as IITA and the International Maize and Wheat Improvement Center, known by its Spanish acronym CIMMYT.

“We try to improve the existing varieties and come up with more that are better than those in the market,” says Peter Setimela, a CIMMYT maize breeder. “With climate change, varieties developed 20 years ago are no longer suitable for the changing environment.” Breeders working under the Drought Tolerant Maize for Africa Initiative led by CIMMYT have developed varieties known as the Kenya Dryland Varieties (KDV) series. KDV 1–6 varieties were released to farmers by the Kenya Agricultural Research Institute (KARI), as well as Freschco and Dryland Seed Companies. The fourth variety of the series is the one now growing on Mativo’s quarter-hectare farm.

It is not only climate change that concerns breeders; they also want to develop varieties that are disease resistant and relevant to the farmers’ other needs – proper milling and cooking quality or flavor, for example. “This is why we have farm trials,” explains Peter Setimela. These trials are done in collaboration with the national research organizations, such as KARI in Kenya. “We look for those traits that farmers prefer. In Kenya, they like white maize for making ugali. In Zimbabwe, some people prefer ZM309 because it is sweet when roasted.”

The seed companies and KARI multiply seeds to furnish supplies adequate to the farmers’ demands, but they also depend on farmers they hire to produce those seeds. “We work with groups of farmers who each have at least 5 acres (2.5 ha),” says Ngila Kimotho, Managing Director of Dryland Seed Company. The seed company clusters the farmers by sublocation and trains them. This, according to Musa Juma, a contract farmer for Dryland in Kibwezi, Eastern Province, is “risk-free planting. This is because you are planting for a known market; as you plant, you don’t have to start worrying about where to sell the produce. An additional perk is that the company provides the seeds.”

Seed companies also use local demonstration farms to show the performance of various maize varieties, winning over farmers to the new varieties that outperform traditional ones. Dryland Seed Company also uses vernacular radio programs to disseminate information on the most productive varieties. “These are interactive shows. We have farmers calling in to find out the best variety to grow, when and where to obtain the seeds,” explains Kimotho. He said that farmers prefer open-pollinated varieties that are early-maturing and drought tolerant and thus better suited to planting in the short rains in the region.

“The basic need in the dry areas is food security,” says Kimotho, adding that farmers sell the surplus grain only when they have a rare bumper harvest. To cater for the diversified market, Dryland markets seeds in packets from 100 g to 1 kg, so there is an affordable option for every farmer. The 100 g package is popular with those who are keen to try out new varieties. “Even students buy it for their parents to try,” says Kimotho. Smallholder farmers, most of whom are women, also choose this option to ensure a subsistence maize crop for their families.

By the same token, farmers are reluctant to place all their trust in a single variety. On Mativo’s farm, he spreads the risk by planting hybrids alongside beans and cowpea. “When the rains are good, the hybrids do well and have high yields, but if the rains are not so good, I still have food from the KDV,” says Mativo. “It would be very sad for a farmer to lack food. When I have food, then my neighbors are also food secure.” Mativo uses ox-drawn plows on his farm, but he also occasionally employs a few manual laborers, some of whom he pays in kind with maize grain, at their request.

In the rare years that farmers get a bumper harvest, they need to sell the surplus. But when there is a plentiful supply, the price of maize is low, and storage becomes an even more vital component of the value chain: the grain requires a pest-free mechanism that also saves the maize from fungal infections, some of which can produce deadly toxins.

Ultimately, every participant in this value chain, the relay race, is focused on one thing–food security. “Working with partners in the national agricultural systems and seed companies, the DTMA program aims to produce 70,000 t of seeds by 2016 with drought tolerant maize varieties in 13 African countries,” said Tsedeke Abate, the Program Leader based in Nairobi. He added that this is enough to plant about 2.8 million ha, an area equivalent to the farms of about 7 million smallholder households.

Two extra-early maturing white maize hybrids released in Nigeria

B. Badu-Apraku,, S.A. Olakojo, G. Olaoye, M. Oyekunle, M.A.B. Fakorede, B.A. Ogunbodede, and S.E. Aladele

Two extra-early maturing hybrids with combined resistance/tolerance to Striga, drought, and low soil nitrogen have been released in Nigeria by the Institute of Agricultural Research and Training (IAR &T) in Nigeria. The extra-early hybrids originally known as IITA Hybrid EEWH-21 and IITA Hybrid EEWH-26 and now designated as Ife Maizehyb-5 and Ife Maizehyb-6 were developed by IITA, and tested extensively in Nigeria in partnership with IAR & T, through the funding support of the Drought Tolerant Maize for Africa (DTMA) Project. The DTMA Project is executed by CIMMYT and IITA with funds provided by the Bill & Melinda Gates Foundation.

Early (90-95 days to maturity) and extra-early (80-85 days to maturity) maize varieties can contribute to food security especially in marginal rainfall areas of West and Central Africa. These varieties are ready for harvest early in the season when other traditional crops such as sorghum and millet are not ready, and are thus used to fill the hunger gap in July in the savanna zone when all food reserves are depleted after the long dry period. Furthermore, there is a high demand for the early and extra-early cultivars in the forest zone for peri-urban maize consumers.

These maize varieties provide farmers the opportunity to market the early crop as green maize at a premium price in addition to being compatible with cassava for intercropping (IITA 1992). However, despite the potential of early and extra-early maize to contribute to food security and increased incomes of farmers in the subregion, maize production and productivity in the savannas are severely constrained by drought, Striga parasitism and low soil-nitrogen.

During the last two decades, IITA in collaboration with national scientists in West and Central Africa, has developed a wide range of high-yielding drought-tolerant and/or escaping extra-early Striga resistant populations (white and yellow endosperm), inbred lines, and cultivars to combat these threats.

Extra-early inbreds and hybrids that are not only tolerant to low N and drought escaping (characteristics of extra earliness) but also possess genes for tolerance to drought during flowering and grain-filling periods are now available in Nigeria (Badu-Apraku and Oyekunle 2012).

Promoting the use of drought tolerant maize in Nigeria

Tahirou Abdoulaye, t. and Onu Anyebe

The DTMA project of IITA-CIMMYT aims at developing and deploying drought tolerant varieties in 13 sub-Saharan African countries. In West Africa, the project, led by IITA and its national partners, is being implemented in Nigeria, Bénin, Mali, and Ghana. In Nigeria, the project covers all the maize-producing agroecologies.

As part of the promotion efforts, farmers’ groups were formed in Kano and Katsina States in northern Nigeria to demonstrate the performance of these improved varieties but also to organize the farmers so that they could have access to the critical inputs needed in maize production.

IITA introduced the drought tolerant variety EVDT 99 to the community of Ruwan Kanya in Rano Local Government Area (LGA) of Kano State, in 2009. This was done as part of the efforts of the DTMA project to inform farmers about drought tolerant maize, both established and newly developed varieties.

A maize production innovation platform was organized around EVDT 99 in the village of Ruwan Kanya. Fourteen farmers initially participated in the production of seeds. For the first year, six farmers each planted 10 kg of the improved variety and eight farmers each planted 5 kg. Other farmers saw the maize fields during the growing season and requested seeds from the participating farmers; eventually the number of participants increased to 36 in 2010. They formed an association to enable them to obtain fertilizer from the State Government.

In the following season, more farmers planted the variety. Six were able to increase their farmland; others bought inputs that increased their production. For example, Alhaji Bako Monitor bought a pair of bullocks for his farm work and for the transportation of goods to the market.

Almost four years later, the DT variety EVDT 99 is now being called Ar Ashiru (named after the president of the farmers’ group). It is grown in the 10 communities in Rano LGA, one community in Sumaila LGA, one community in Tudun Wada LGA, all in Kano State and in Soba/Risipa in Kaduna State. Other communities in Kano State that got EVDT 99 from Ruwan Kanya LGA include Gidan Zangi, Garabi, Doka, Zazaye, Takalafia, Gana, Kajorawa, Yelwa ciki, Tadesha, and Kundu.

Some farmers also planted EVDT 99 in the dry season after harvesting tomatoes between February/March. The dry season maize is harvested fresh and consumed after being roasted or boiled.

The farmers’ association in Ruwan Kanya was linked to the Kano State Government in 2010. The members were able to purchase subsidized fertilizer at 1100 naira/bag (~US$7) including transportation to the village. The following year, in 2011, the government changed; the new government did not allocate fertilizer to the farmers’ group. The farmers put their money together and the project helped by linking them with a dealer who provided good quality input. They bought the fertilizer in bulk at 5000 naira (~$31) for NPK and 5200 naira for urea and continued seed production.

The farmers say that they appreciate the productivity and earliness of the variety. EVDT 99 responds well to fertilizer and those growing it have had no problem in getting the fertilizer they need to apply.

During the new phase of DTMA, the project team is focusing on getting these farmers linked to seed companies so they can renew their seed stock and continue to purchase quality certified seeds. The drought tolerant maize varieties and hybrids are now being produced and sold by some seed companies in Nigeria, thanks to the efforts of these farmers.

Farmers need to be made aware of the need to renew their seed stock regularly including seeds for open-pollinated varieties such as EVDT to maintain the purity and productivity level of their cultivars.