The CGIAR Research Program on Maize (MAIZE) has been designed to generate and provide new technologies, know-how, methodologies, and novel tools. The program has been organized around nine strategic initiatives that house sets of activities. IITA has been implementing activities clustered around the various strategic initiatives in West and Central Africa for the last 2 years. The highlights for 2013 are presented here.
Germplasm development, testing, validation, and release
Monitoring genetic gain in breeding for drought tolerance
One of the major goals of the joint IITA/CIMMYT project Drought Tolerant Maize for Africa (DTMA), funded by the Bill & Melinda Gates Foundation, has been the development of maize open-pollinated varieties (OPVs) and hybrids that produce under drought at least 1 t/ha more than the hybrids and OPVs commonly grown in 2006. A comparative trial showed that the varieties developed between 2007 and 2010 had 22% and 13% higher yields, respectively, compared with earlier varieties. In a second trial, comparing late-maturing, three-way cross hybrids developed in 2011/2012 with commercial hybrids, the best three-way crosses produced 54% more grain yield under drought and 23% more under irrigation compared with the commercial hybrids. The best three-way cross hybrids were also shown to significantly outyield commercial hybrids in follow-up trials in Benin Republic, Ghana, Mali, and Nigeria. The increases in grain yields were not associated with significant changes in other major agronomic traits.
Molecular markers for identifying homozygous and homogeneous maize inbred lines
More than 400 early and extra-early maturing and intermediate and late-maturing maize inbred lines were genotyped by genotype-by-sequencing at Cornell University. The intermediate and late maturity group included 125 Striga resistant and 190 drought tolerant maize inbred lines. Single-nucleotide polymorphism (SNPs) analysis showed that the majority of the lines of the intermediate and late maturity group had less than 10% heterozygosity. Some parental lines of hybrids have been selected for further inbreeding to develop fixed lines. Phylogenetic trees constructed using SNPs will be used to identify the heterotic affinities of the lines for use in developing hybrids and breeding populations.
Channeling drought tolerant products to partners
In 2013, almost 400 sets of regional trials were dispatched to partners in West and Central Africa for testing. Maize varieties and hybrids were selected from these trials for validation tests in 2013 in Benin Republic, Ghana, Mali, and Nigeria. The results were used to recommend the best drought tolerant varieties and hybrids for registration and release in the countries. In collaboration with partners in Nigeria, two extra-early maturing hybrids and one later maturing drought tolerant yellow OPV were released in 2013. Also, two early maturing hybrids resistant to Striga and tolerant of drought and low soil nitrogen were released in Mali as Sanu and Mata.
Identifying maize hybrids with enhanced pro-vitamin A levels
A regional trial composed of hybrids formed from inbred lines with intermediate to high levels of pro-vitamin A was dispatched to partners for evaluation. Results of carotenoid analysis showed that almost all hybrids included in this trial had significantly higher levels of pro-vitamin A compared with a commonly grown orange commercial hybrid (Oba Super II) in Nigeria. The best 10 hybrids were comparable to Oba Super II in mean grain yield and six hybrids had pro-vitamin A concentrations which were 55 to 146% higher than those of Oba Super II. The most promising pro-vitamin A hybrids will be further tested in national performance and on-farm trials to generate data for variety registration and release.
Seed supply to accelerate deployment
Access to productive and new stress-tolerant varieties and hybrids by the national agricultural research systems (NARS) and the private seed companies is important for the production and marketing of good quality seeds to farmers. In 2013, NARS, community based seed producers, and private seed companies were supplied with seeds of extra-early (>12 t), early (>2 t), and intermediate/late-maturing (<8 tons) drought tolerant maize varieties that in turn generated at least 2500 t of foundation seeds. In addition, 1.3 tons of three registered Striga resistant maize varieties were supplied to partners for demonstrations in northern Nigeria and for further multiplication by the community based seed producers and emerging seed companies.
One objective of the agricultural transformation initiative of the Federal Government of Nigeria is to increase the use of improved seeds by supporting research institutes to supply breeder and foundation seeds to registered seed companies for the production of certified seeds. IITA is fully committed to the initiative and also in assisting the national research partners to produce and supply seeds to seed companies. In 2013, more than 40 tons of foundation seeds of several recently released maize varieties were produced by IITA for further multiplication and dissemination to farmers.
Incorporating legumes in maize-based farming system
A trial involving the rotation of maize with soybean and cowpea was evaluated at two sites in Mozambique for 2 years. At both sites, the soybean-maize and cowpea-maize rotations significantly increased maize grain yield and produced more maize residue, compared with maize after maize rotation. The benefits of previous soybean and cowpea crops to succeeding maize may be likely to be attributable to the legumes providing residual nitrogen, organic carbon, and other benefits including a reduction in pest and disease pressure.
Maize stem borer
On-farm trials were conducted in Benin Republic to assess the efficiency of an egg delivery system of the parasitoid Trichogrammatoidea eldanae to plants for controlling stem borers. The pest population pressure from stem borers was quite high in 2013 but the parasitoids were still able to significantly reduce populations, particularly of Eldana saccharina, leading to a higher average grain yield in the trichogramma-treated plots.
Maize streak virus disease
Maize inbred lines were artificially inoculated with the maize streak virus disease and disease severity was scored for 6 weeks. Among the 157 lines, 41% showed resistant reactions whereas 30% were susceptible to the virus. Resistant lines are currently being used to develop hybrids and synthetic varieties.
The identification of fungal strains for biocontrol to reduce aflatoxin contamination in maize starts with field collections of Aspergillus flavus strains from major maize production zones. In 2013, maize samples were collected in Ghana, Mozambique, and Tanzania. Atoxigenic (non-toxin producing) strains identified from each country were purified and sent to the USDA-ARS laboratory in Arizona to determine their genetic diversity. Country-specific atoxigenic strains were selected as candidates for efficacy testing to identify the most competitive strains capable of displacing the aflatoxin-producing strains. The final biocontrol product contains a mixture of strains effective in reducing aflatoxins in maize across a broad range of environments in the country. Strains isolated from each country will be pooled to create regional biocontrol products.
Striga – biocontrol
As part of Integrated Striga Management in Africa (ISMA), funded by the Gates Foundation, the efficacy of a Striga biocontrol product, Fusarium oxysporum f. sp. strigae (Fos), was evaluated under natural and artificial infestation in northern Nigeria. Seeds of resistant and susceptible maize varieties were coated with Fos inoculum prior to planting and the emergence and number of flowering Striga were scored during the growing season. Biocontrol in combination with Striga resistant maize reduced emergence by 73% compared with the susceptible control, and by 39% compared with the resistant variety without the biocontrol agent. Biocontrol in combination with the susceptible variety significantly reduced emergence by 53%, resulting in 42% reduction in the number of flowering plants and in an increase of 21% in grain yield compared with the susceptible control (i.e., without biocontrol). The observed reduction in Striga emergence across maize varieties and the increase in grain yield are indicators of the effectiveness of the biocontrol product.
Striga – nitrogen
The response to nitrogen fertilizer of early maturing, drought resistant and Striga resistant maize varieties was evaluated in northern Nigeria. Two nitrogen-use efficient varieties, identified from these trials, are now being tested on-farm to confirm their performance for release in Nigeria.
Gender-based participatory evaluation of varieties
Studies of preferences for drought tolerant maize varieties and hybrids among men and women farmers in Benin Republic, Ghana, Mali, and Nigeria showed that preferences differ among countries and groups. In Benin Republic, for example, yield is the most important criterion for both men and women farmers, but men tended to also emphasize color as it relates to market demand while women tended to emphasize characteristics for nutrition and processing. The results of these studies will be used to modify the selection criteria for breeding and for better targeting of varieties for male and female farmers. Studies were also conducted to assist seed companies with training on developing strategies for assessing the market potential of gender focused, innovative, cost-effective, and timely seed supply.
Gender-based adoption pattern studies
A gender-based adoption pattern study found that women prefer early maturing and nutritionally enhanced varieties whereas men prefer high-yielding varieties. The socioeconomic heterogeneity of men and women and the diverse and complementary choices of both gender groups should be taken into consideration in planning a study to obtain comprehensive adoption patterns.