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Badu-Apraku B.,International Institute Of Tropical Agriculture | Badu-Apraku B.,IITA Ltd | Lum A.F.,University of Buea
Agronomy Journal | Year: 2010

Maize (Zea mays L.) cultivars combining high grain yield with elevated levels of lysine, tryptophan, and desirable endosperm modification, could reduce food insecurity and malnutrition in West and Central Africa (WCA). Sixteen early- and nine extra-early-maturing quality protein maize (QPM) and normal cultivars were evaluated under Striga hermonthica (Del.) Benth infes-tation and Striga-free environments in Nigeria from 2006 to 2008 to identify stable and high yielding cultivars. The extra-early normal maize cultivars 2000 Syn EE-W STR and 99 TZEF-Y STR, were similar in yield to the QPM versions under both research conditions. While TZEE-Y Pop STR C4 was superior in grain yield to its QPM version only under Striga-free conditions, TZEE-W Pop STR C4 significantly outyielded the QPM version, under both test conditions and was superior in Striga resistance. In the early maturity group, TZE-W DT STR C4 outyielded the QPM version by 21% under Striga infestation and by 10% when Striga-free. In contrast, the QPM cultivar 98 Syn WEC STR QPM C0 outyielded the normal endosperm version by 31% when Striga-infested. GGE-biplot analysis demonstrated that two extra-early and three early maturing cultivars had outstanding per-formance in both research environments. TZEE-W Pop STR QPM C0 and EV DT-W 99 STR QPM C0 were high-yielding and stable when Striga-infested while TZE-Y Pop DT STR C4, TZE-W Pop DT STR C4, and TZE-Y Pop STR QPM C0 were supe-rior when Striga-free. The QPM cultivars with grain yield performance and Striga resistance comparable or superior to those of their normal endosperm versions have been developed in our program. © 2010 by the American Society of Agronomy.


Kamara A.Y.,International Institute Of Tropical Agriculture | Kamara A.Y.,IITA Ltd | Ewansiha S.U.,University of Benin | Menkir A.,International Institute Of Tropical Agriculture | Menkir A.,IITA Ltd
Archives of Agronomy and Soil Science | Year: 2014

Maize (Zea mays L.) is an important food crop in the Guinea savannas of Nigeria. Despite its high production potential, drought, Striga hermonthica parasitsim, and poor soil fertility particularly nitrogen deficiency limit maize production in the savannas. Breeders at IITA have developed drought- and Striga-tolerant cultivars for testing, dissemination, and deployment in the region. Information on the response of these cultivars to N fertilization is, however, not available. This study evaluated grain yield, total N uptake (TNU), N uptake (NUPE), N utilization (NUTE), and N use efficiency (NUE) of selected maize cultivars along with a widely grown improved maize cultivar at two locations in the Guinea savannas of northern Nigeria. Maize grain yield increased with N application. The average grain yield of the maize cultivars was 76% higher at 30, 156% higher at 60, and 203% higher at 120 kg N ha-1 than at 0 kg N ha-1. This suggests that N is a limiting nutrient in the Nigerian savannas. Five drought-tolerant cultivars produced consistently higher yields when N was added at all levels. These cultivars had either high NUPE or NUTE confirming earlier reports that high N uptake or NUTE improves maize grain yield. The study also confirms earlier reports that maize cultivars that are selected for tolerance to drought are also efficient in uptake and use of N fertilizer. This means that these cultivars can be grown with application of less N fertilizer thereby reducing investment on fertilizers and reduction in environmental pollution. © 2013 © Taylor & Francis.


Menkir A.,International Institute Of Tropical Agriculture | Menkir A.,IITA Ltd | Crossa J.,International Maize and Wheat Improvement Center | Meseka S.,International Institute Of Tropical Agriculture | And 7 more authors.
Euphytica | Year: 2016

Drought occurs at high frequency in maize production zones in Africa. Carefully controlled moisture deficits have been imposed at anthesis and grain filling stages of maize to develop drought tolerant germplasm. The present study was conducted to examine the potential effects of drought tolerant parents selected under such managed drought stress on agronomic performance of their top-cross hybrids across variable growing conditions in the rainy season. Three independent trials consisting of top-cross hybrids involving drought tolerant parents and commercial hybrids were evaluated under manged drought stress (MDS) and well watered (WW) condition at Ikenne in Nigeria for 3 years during the dry season and across 30 stressful (SE) and 52 favourable (FE) rainfed environments in West Africa. The drought stress imposed in the dry season caused a 53–64 % annual average yield reductions in these trials. In spite of these, about 56 % of the top-crosses produced high grain yields under MDS and WW conditions. The rank orders for hybrid grain yields did not change markedly across different years under MDS and WW conditions. Also, nearly 78 % of the top-crosses produced high grain yields across SE and FE environments in the rainy season. Sixteen top-cross hybrids amongst these were present in the top yielding groups under the MDS environment. Some high yielding top-crosses with stable performance across variable rainfed environments were identified in the current study. The phenotypic and genetic correlations between grain yield under MDS and that under SE environment were positive and moderate. Also, the phenotypic and genetic correlations showed that the capacity of top-cross hybrids to produce high grain yields under MDS was independent of the yield potential under FE environment. These results suggest that selection of parents under manged drought stress promotes the development of top-cross hybrids broadly adapted to variable rainfed conditions. © 2016 Springer Science+Business Media Dordrecht


Menkir A.,International Institute Of Tropical Agriculture | Menkir A.,IITA Ltd
Crop Science | Year: 2011

Striga hermonthica (Delile) Benth. is a parasitic weed damaging maize and other cereals in Africa. Although S. hermonthica-resistant inbred lines were developed from diverse sources, the effect of their diversity on heterosis under parasite pressure has not been investigated. Sixty-four hybrids were produced from 16 resistant and four susceptible inbreds using a factorial mating in sets crossing scheme. The hybrids and their parents were evaluated in separate trials with and without S. hermonthica infestation at four environments in Nigeria. Genotypic differences among both inbreds and hybrids were significant for all measured traits under infestation. The hybrids displayed a broad range of midparent heterosis (MPH) for most traits measured under S. hermonthica-infested and noninfested conditions. Mean grain yield and agronomic performance of resistant × resistant cross hybrids were superior to that of susceptible × resistant cross hybrids in the presence of S. hermonthica but not in the absence of the parasite. Correlations between midparent values and hybrid means were large and positive for grain yield but were small for plant height and days to silking. Marker-based genetic distances of parental lines were not correlated with MPH of all traits recorded under S. hermonthica infestation. Selection for inbreds with greater levels of resistance to S. hermonthica appears to be more effective for developing resistant hybrids than selection of parental pairs based on genetic distance alone. © Crop Science Society of America.


Menkir A.,International Institute Of Tropical Agriculture | Menkir A.,IITA Ltd | Rocheford T.,Purdue University | Maziya-Dixon B.,International Institute Of Tropical Agriculture | Tanumihardjo S.,University of Wisconsin - Madison
Euphytica | Year: 2015

The nutritional value and health benefits derived from carotenoids have prompted increased investment in breeding crop varieties with elevated carotenoid levels for areas where crops like maize with low nutrient density are consumed in large quantities. Twelve exotic donor lines of high β-carotene were crossed to seven elite tropical yellow or orange lines and the F1s were backcrossed to the same or different elite line. Ninety-eight lines derived from these backcrosses (BC), seven recurrent parents, and 24 adapted lines derived from other source populations were included in a trial grown at Ibadan in Nigeria for three years. Carotenoid analyses of samples harvested from this trial found significant differences in accumulating provitamin-A and other carotenoids among lines, which were consistently expressed across years. The lines also displayed distinct carotenoid profiles. Among the best 25 inbred lines containing 5.0–16.6 μg g−1 β-carotene and 8.0–17.4 μg g−1 pro-vitamin A, 24 were BC-derived lines and one was derived from a bi-parental cross of tropical yellow elite lines. The best BC-derived lines accumulated 23–313 % more β-carotene and 32–190 % more provitamin-A than the recurrent parents. These BC-derived lines may be valuable resources for favorable alleles to develop maize varieties with high provitamin-A and for genetic studies to understand the underlying mechanisms regulating carotenoid biosynthesis. These results illustrate the effectiveness of exploiting natural allelic diversity existing in exotic lines through backcrossing combined with visual selection for bright yellow to orange kernel color with semi-flint to flint kernel texture in boosting provitamin-A to a new level in tropical maize. © 2015, Springer Science+Business Media Dordrecht.

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