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Striga hermonthica (Del.) Benth infestation is one of the major constraints to maize production in the Nigeria savannas. The application of nitrogen fertilizer to Striga-resistant hybrids may reduce Striga infection and increase grain yields. The objective of this study was to assess the performance of six maize hybrids at low (30 kg ha−1) and high (120 kg ha−1) nitrogen application under natural infestation with Striga in northern Nigeria in 2014 and 2015. The two nitrogen rates and the six hybrids were arranged in a split-plot design with three replications. The nitrogen treatment was assigned to the main plot while the maize hybrids were assigned to the subplot. Data were collected on number of emerged Striga plants, Striga damage score, total dry matter and grain yield. Results showed that the application of nitrogen at 120 kg ha−1 reduced the number of Striga plants by 58% compared to application at 30 kg N ha−1 in Kafin Madaki and by 48% in Tudun Wada. Nitrogen application at 120 kg N ha−1 also reduced Striga damage rating by 22% in Kafin Madaki and by 33% in Tudun Wada. Both the commercial hybrid (OBASUPER 1) and the susceptible hybrid (8338-1) exhibited higher Striga damage ratings compared to the new hybrids at both locations. Grain yield was 86 and 98% higher in Kafin Madaki and Tudun Wada, respectively, when N was applied at 120 kg N ha−1 than at 30 kg N ha−1. The hybrids M1124-3 and M1227-14 produced grain yields that were significantly higher than those of the other hybrids in all locations. Our results showed that the application of 120 kg N ha−1 to Striga-resistant maize hybrids will reduce Striga infection and increase grain yield.

Increasing delays in the onset of the rainy season and extended dry spells in the Nigerian savannas are complicating the determination of optimal planting dates for rain-fed crops, which increases risks for farmers. This study evaluated the impact of planting dates on soybean [Glycine max (L.) Merr.] performance to identify optimal planting dates for different soybean varieties in two agroecological zones (AEZs) of Nigeria. The study involved six planting dates (15 June, 22 June, 29 June, 6 July, 13 July, and 20 July) and three soybean varieties (TGX-1835-10E, TGX-1951-3F, TGX-1904-6F). Results showed significant differences in growth and yield parameters based on location, variety, and planting date. In the Sudan savanna (SS), AEZ at BUK-Kano, optimal yields (>1500 kg ha−1) were achieved when planting TGX-1835-10E and TGX-1951-3F from 15 to 29 June and TGX-1904-6F on 15 June. Planting beyond 29 June reduces yields by 12–55% for TGX-1835-10E and 27–63% for TGX-1951-3F. For TGX-1904-6F, planting after 15 June reduces yields by 27–90%. In the Northern Guinea savanna (NGS) AEZ at Zaria, optimal yields (>1500 kg ha−1) were obtained when planting TGX-1835-10E and TGX-1951-3F from 15 June to 6 July, and TGX-1904-6F between 15 to 29 June. Delaying planting beyond these dates significantly reduced yields by 18–31% for TGX-1835-10E and 12–20% for TGX-1951-3F and 10–41% for TGX-1904-6F. [ABSTRACT FROM AUTHOR]

Historically, conventional breeding has been the primary strategy used to develop a number of Striga-resistant varieties currently grown in the Sahel of Western Africa. In this study, we have successfully developed and applied a marker-assisted selection strategy that employs a single backcross programme to introgress Striga resistance into farmer preferred varieties of cowpea for the Nigeria savannas. In this strategy, we have introduced the Striga resistance gene from the donor parent IT97K-499-35 into an elite farmer preferred cowpea cultivar 'Borno Brown'. The selected 47 BC1F2 populations confirmed the recombinants with desirable progeny having Striga resistance gene(s). The 28 lines selected in the BC1F2:4 generation with large seed size, brown seed coat colour and carrying marker alleles were evaluated in the field for resistance to Striga resistance. This led to the selection of a number of desirable improved lines that were immune to Striga having local genetic background with higher yield than those of their parents and standard varieties. [ABSTRACT FROM AUTHOR]

Soybean (Glycine max) is a major cash crop in the savannas of Nigeria although productivity is typically constrained by poor soil fertility. The objective of this research was to determine the interactive effect of N and P on soybean productivity in the northern Guinea and Sudan savannas of northeast Nigeria. Experiments were conducted using locally adapted early and late maturing cultivars. Two rates of N and three rates of P fertilizer were also compared at both sites over two years. At both sites, pods plant−1 and seed yield were higher in 2006 than in 2007, possibly due to better rainfall distribution in 2006. Nitrogen fertilizer had no significant effect on seed yield or pods plant−1. Application of P fertilizer increased pods plant−1 by 40–66%. Averaged across site and year, seed yield with no P was 1057.2 kg ha−1 while yield with 20 and 40 kg ha−1 P were 1941.0 kg ha−1 and 2371.5 kg ha−1, respectively. No significant interaction effect between N and P fertilizer on seed yield and pods plant−1 was observed. The late maturing cultivar yielded less than the earlier maturity group cultivar in 2007 likely due to moisture stress. For optimum seed yield 40 kg of P fertilizer ha−1 is recommended for soybean production in both locations. Our results suggest that N fertilizer is not critical for soybean production in this area. [ABSTRACT FROM PUBLISHER]

Knowledge of the genetic structure and diversity of germplasm collections is crucial for sustainable genetic improvement through hybridization programs and rapid adaptation to changing breeding objectives. The objective of this study was to determine the genetic diversity and population structure of 281 International Institute of Tropical Agriculture (IITA) soybean accessions using diversity array technology (DArT) and single nucleotide polymorphism (SNP) markers for the efficient utilization of these accessions. From the results, the SNP and DArT markers were well distributed across the 20 soybean chromosomes. The cluster and principal component analyses revealed the genetic diversity among the 281 accessions by grouping them into two stratifications, a grouping that was also evident from the population structure analysis, which divided the 281 accessions into two distinct groups. The analysis of molecular variance revealed that 97% and 98% of the genetic variances using SNP and DArT markers, respectively, were within the population. Genetic diversity indices such as Shannon's diversity index, diversity and unbiased diversity revealed the diversity among the different populations of the soybean accessions. The SNP and DArT markers used provided similar information on the structure, diversity and polymorphism of the accessions, which indicates the applicability of the DArT marker in genetic diversity studies. Our study provides information about the genetic structure and diversity of the IITA soybean accessions that will allow for the efficient utilization of these accessions in soybean improvement programs, especially in Africa. [ABSTRACT FROM AUTHOR]