Lucky O. Omoigui

Field performance of improved cowpea varieties under conditions of natural infestation by the parasitic weed Striga gesnerioides

Cowpea is an important food crop in the dry savannas of West and Central Africa because of its high protein content. Yields are, however, considerably reduced by the parasitic angiosperm Striga gesnerioides. Field trials over 2 years in two localities in northeast Nigeria evaluated the performance of diverse cowpea varieties under conditions of natural infestation by Striga. Grain yield was higher in Tilla than in Damboa where the higher Striga infestation may be caused by the lower rainfall and the sandy nature of the soils. Two varieties (IT97K-499-35 and IT90K-82-2) were confirmed to be resistant to Striga. Yield gain from IT97K-499-35 over the local variety ranged from 30% in Tilla in the northern Guinea savanna to 126% in Damboa in the Sudan savanna. The local variety Borno Brown and two improved varieties were found to be as susceptible to Striga as the susceptible control, TVX-3236, and therefore may not be recommended for cultivation in areas where Striga infestation is a problem. One variety, reported previously to be resistant to one or two races of Striga supported moderate levels of emerged Striga, suggesting that it is not totally resistant to the Striga race in the two localities. However, it produced grain yields that were comparable to the resistant varieties in the locality that was most infested, suggesting that it is tolerant to Striga. There are concerns about the adoption potential of the Striga-resistant variety IT97K-499-35 because of its medium-sized white seeds. Farmers in this zone prefer large-seeded brown cowpea. We recommend that efforts be made to develop Striga-resistant varieties that satisfy end-user preferences.

A PARTICIPATORY APPROACH TO INCREASING PRODUCTIVITY OF MAIZE THROUGH STRIGA HERMONTHICA CONTROL IN NORTHEAST NIGERIA

SUMMARY Striga hermonthica is a parasitic weed that attacks maize, sorghum and other staple cereal crops and has long been considered one of the greatest biotic constraints to cereal production in Africa. Use of resistant or tolerant maize varieties, a maize–legume rotation using trap crops that stimulate suicidal germination of Striga and the application of nitrogen fertilizer are all effective in reducing infestation and damage. This paper reports on the use of a participatory research and extension approach in assessing the performance and scaling-up of integrated Striga control packages in three agro-ecological zones in Borno State, Nigeria. The participatory process which encourages close interaction between research, extension and farmers, involved 30 local communities and 228 farmers representing 193 farmer groups in identifying their own problems and seeking solutions to them. Results showed not only effective Striga control but productivity increases of over 200%. The involvement of local farmers and groups in the evaluation process, firstly, helped to confirm that Striga control can best be achieved using soyabean followed by Striga-resistant maize together with productivity-increasing management practices and, secondly, promoted farmer-to-farmer extension. A participatory adoption assessment exercise indicated widespread adoption of new varieties and management practices, despite the need for increased labour. Great potential exists to scale out the results to similar areas of Guinea and Sudan savannas in the West Africa region.

Integrating planting date with insecticide spraying regimes to manage insect pests of cowpea in north-eastern Nigeria.

We sought to establish the most effective combination of planting dates with insecticide spraying regimes for the management of insect pests of cowpea in the savannas of northeast Nigeria. The results after 3 sprays, made once each at the bud initiation, flowering, and podding stages, did not differ significantly from those after 2 sprays, made once each at flowering and podding, in terms of reducing insect pest population and increasing grain yield. Despite the reduction in insect infestation, delaying planting beyond mid-August reduced cowpea grain yield by 12.3%, on average. The yield of the medium-maturing variety IT89KD-391 was significantly higher when planted in mid-August and sprayed twice than when planted on the earlier or later dates. The yield of the indeterminate late-maturing variety ITKD89-288 was higher when planted in early August and sprayed thrice. Early- and medium-maturing cowpea varieties should therefore be planted in mid-August and sprayed twice. Late-maturing indeterminate varieties should be planted in early August and sprayed thrice.

Influence of phosphorus application on growth and yield of soybean genotypes in the tropical savannas of northeast Nigeria

Abstract The cultivation of soybean is increasing in the savannas of Nigeria due to its widespread use in the food and feed industry. Production is, however, constrained by low soil phosphorus (P) levels in northeast Nigeria. This study evaluated four soybean varieties for their response to three rates of P in two agro-ecozones in 2004 and 2005. Experimental design was a split-plot arrangement of treatments with three replications. The main plots were assigned the P treatments and subplots were soybean cultivars randomised within the main plots. The studies found that soybean responds to P application but differences between 20 and 40 kg P/ha were not significant, despite low test P levels. This may be due to limitations in other nutrients. More studies are needed to determine the synergistic effect of P and other nutrients on soybean growth and yield. Soybean growth and seed yield were lower in 2004 than in 2005 because trials were established comparatively late in 2004 and crops were therefore affected by late season moisture stress. There is, therefore, a need to establish the appropriate time for planting soybean in these zones. Late maturing varieties produced higher yields than early maturing varieties in 2005 probably due to early planting which allowed full use of the growing season.

Influence of nitrogen fertilization on the performance of early and late maturing maize varieties under natural infestation with Striga hermonthica (Del.) Benth

Field studies were conducted in northeast Nigeria to evaluate the response of early and late-maturing maize varieties infested with natural populations of Striga to different rates of nitrogen (N) fertilizer. There were significant reductions in the number of emerged Striga at 120 kg N ha−1 for the early varieties and at 60 and 120 kg N ha−1 for the late varieties. The number of emerged Striga only significantly differed among the late varieties. Averaged across varieties, grain yield of the early varieties was 144% higher at 60 kg N ha−1 and 192% higher at 120 kg N ha−1 than without added N. For the late varieties the increase in grain yield was 85% higher at 60 kg N ha−1 and 144% higher at 120 kg N ha−1 than without added N. Among the early varieties, TZE COMP4 C3 had significantly lower grain yield than the other varieties. Among the late varieties, grain yields of 8338-1-1 and TZB-SR were significantly lower than in the other varieties. Our results show that the application of 60–120 kg N/ha to Striga resistant or tolerant varieties may reduce damage and increase grain yield. Higher economic rates of return was obtained at N rates of 60–120 kg N/ha than the other rates.

New sources of aphids [Aphis craccivora (Koch)] resistance in cowpea germplasm using phenotypic and molecular marker approaches

This study sought to identify new sources of resistance to cowpea aphids (CPA) using molecular and phenotypic approaches and the inheritance pattern. Sixty cowpea genotypes were phenotyped for resistance to CPA using insect proof cages and further confirmed using markers linked to aphid resistance. Result revealed that among the cowpea genotypes, TVu 2897 and TVNu 1158 supported lowest number of aphids and plant damage scores. The seedlings of these genotypes also had high level of survival rates and were completely healthy with normal growth. This indicates that these genotypes are resistant to aphid attacks. However, the resistance in TVNu 1158 did not seem strong compared to the genotype TVU 2897 that was confirmed to be resistant to multiple aphid biotypes. The mechanism of resistance in TVu 2897 and TVNu 1158 were expressed as a hypersensitive response at the site of infestation on the leaves. The other genotypes especially Aloka local and keffi local supported the highest number of aphids, damage score and low level of survival rate, suggesting that they are susceptible to aphid attack. The cowpea genotype IT84S-224-6 previously reported to be resistant to aphids supported high number of aphids and was marked by stunted growth and high mortality rate. Molecular and phenotypic screening revealed that TVu-2876 has a strong resistance to cowpea aphid and should be a good source of resistance gene that can be used in breeding to develop new aphid resistant cowpea cultivars. Although, the results of phenotypic tests and molecular marker detection agreed in most cases, molecular markers detection was found more reliable in identifying genotypes for resistance to CPA. The segregation in F2 and BC1 populations derived from the cross between TVNu 2876 and Keffi local indicated that resistance to cowpea aphids in TVu-2876 is controlled by a single dominant gene. Allelism test revealed that resistance gene in TVNu 2876 is non-allelic with the gene that confers resistance in SARC 1-57-2 and TVNu 1158.

Genomics, genetics and breeding of tropical legumes for better livelihoods of smallholder farmers

Abstract Legumes are important components of sustainable agricultural production, food, nutrition and income systems of developing countries. In spite of their importance, legume crop production is challenged by a number of biotic (diseases and pests) and abiotic stresses (heat, frost, drought and salinity), edaphic factors (associated with soil nutrient deficits) and policy issues (where less emphasis is put on legumes compared to priority starchy staples). Significant research and development work have been done in the past decade on important grain legumes through collaborative bilateral and multilateral projects as well as the CGIAR Research Program on Grain Legumes (CRP‐GL). Through these initiatives, genomic resources and genomic tools such as draft genome sequence, resequencing data, large‐scale genomewide markers, dense genetic maps, quantitative trait loci (QTLs) and diagnostic markers have been developed for further use in multiple genetic and breeding applications. Also, these mega‐initiatives facilitated release of a number of new varieties and also dissemination of on‐the‐shelf varieties to the farmers. More efforts are needed to enhance genetic gains by reducing the time required in cultivar development through integration of genomics‐assisted breeding approaches and rapid generation advancement.

Character Association Studies in Groundnut (Arachis hypogaea L.)

The aim of this study was to evaluate the degree of relationship and association amongst morphological characters of groundnut as an important food crop in Nigeria. 118 cultivars were planted in a completely randomized design structure. Characterization was based on qualitative and quantitative evaluations of 62 characters. Data were analysed on the SPSS software (20.0 versions). Correlation tools were applied using Spearman, Kendall and Pearson methods. Level of relationship was determined based on the strength of coefficients R. Dependence among traits was tested using the Chi square. Multiple regression analysis was carried out in a predictive model. As a result, many of the traits are very weakly correlated. Day to emergence has no effect on Day to 50% flowering (R = 0.237, p 0.6, p < 0.9) were observed amongst pod and seed parameters. Pod sizes significantly affect the number of seeds present (R = 0.551, p < 0.01) with R2 of 30%. Qualitative traits have no effect on each other as all coefficients are very low. Pod constriction and sizes have no relationship (R = -0.029). Tolerance to diseases is not affected by any qualitative trait. Also, no trait determines seed colour. Pubescence of young and mature leaflets recorded the only high positive correlation among all qualitative traits (R = 0.837, p = 0.01). However, leaf and stem pubescence have no relationship. The following traits significantly depend on cultivar type: disease tolerance (χ2 = 17.93, p = 0.000), plant survivorship (χ2 = 39.97, p = 0.000) and pod yield (χ2 = 69.695, p = 0.008). Seed yield has been predicted in a fit model with R2 of 51% and significant p values (p < 0.05) among some predictors. When appropriately applied, the information provided in this report may be useful to groundnut growers and breeders as well those interested in systematic studies of the crop.