International Institute Of Tropical Agriculture Research Articles

Above-ground carbon stock estimation using pleiades satellite imagery of the secondary forest ecosystem in Ibadan, Nigeria

Secondary forest ecosystem contributes to global climate change mitigation through carbon sequestration. Above-Ground Biomass (AGB) is the major component for monitoring and estimating Carbon Stocks (CS) and fluxes in tropical forests. However, information on Above-Ground Carbon Stock (AGCS) for the International Institute of Tropical Agriculture (IITA), which hosts relics of the undisturbed secondary forest ecosystem in south-western Nigeria, has not been documented. Therefore, AGCS of the secondary forest ecosystem was estimated using remote sensing techniques. Pleiades satellite data were used for this study. One hundred and forty plots of 50m x 50m were laid in IITA secondary forest using systematic sampling technique at 10% sampling intensity. Pleiades satellite imagery was acquired using Remote Sensing (RS) technique and spectral data for each sample plot extracted. The spectral indices used for AGB estimation were: Normalised Difference Vegetation Index (NDVI), Difference Vegetation Index (DVI), Infrared Percentage Vegetation Index (IPVI), Optimised Soil Adjusted Vegetation Index (OSAVI) and Re-normalised Difference Vegetation Index (RDVI). Regression equation was used for the prediction of AGB from where the total CS estimate was obtained. Data were analysed using descriptive statistics and linear regression analysis. The AGB and CS ranged from 101.06 to 881,834.92 kg/ha and 50.53 to 440,917.46 kg/ha, respectively. The DVI had the highest AGB value which ranged from 187 to 15,577 kg/ha, followed by IPVI, RDVI and OSAVI which ranged from 7,561 to 12,324 kg/ha, 64.0591 to 133.178 kg/ha, 0.0134 to 0.5621 kg/ha, respectively, while NDVI had the least values which ranged from -0.01 to 0.48 kg/ha. The best AGB estimation model was AGB = exp. (3,496.61 + 0.99 x (RDVI) 1/2); Coefficient of Determination (R2) = 0.93, Bayesian Information Criterion (BIC) = 82.34). The total carbon stock ranged from 11,035 to 18,774 kg/ha. Model with re-normalized difference vegetation index was most suitable among other indices for estimating above-ground carbon stock. Therefore, effective integration of different sensor data will be an important research topic for improving above-ground biomass estimation performance.

Genetic Variability for Flowering Time, Maturity and Drought Tolerance in Cowpea [Vigna unguiculata (L.) Walp.]: A Review Paper

Background: Cowpea plays a critical role in the lives of millions of people in Africa and other parts of the developing world, where it is a major source of dietary protein that nutritionally complements staple low-protein cereal and tuber crops. It is a valuable and dependable commodity that produces income for farmers and traders. Objective: To review related research work on the genetic variability for time to flowering, maturity and drought tolerance in cowpea.
 Data Source: Searches were made from the following databases and archives; International Institute of Tropical Agriculture (IITA), The Essential Electronic Agricultural Library (TEAL), Access to Global Online Research in Agriculture (AGORA) (FAO), AGRICOLA (National Agricultural Library), AGRIS - Agricultural Sciences and Technology (FAO), CAS - Chemical Abstracts (ACS), DOAJ - Directory of Open Access Journals, CABI, Euphytica, Elsevier, Research Alert, Scopus and CGIAR, Plant Genetics and Breeding Database, Crop Science Database, Plant Genetics and Breeding Database, data base repositories, using the terms “genetic variability”, “drought”, “tolerance”, “ time to flowering and maturity”, and “cowpea” individually or in combination to identify literature published in English language between January 1990 to January 2018.
 Methods: The review was carried out using the above search terms. Research papers were critically reviewed, relevant data extracted, and a narrative synthesis was conducted to determine the relevant papers.
 Results: In all 150 papers met the inclusion criteria. Collections were from varied background; Sub-Saharan Africa, Asia, Europe, and Latin Americas.
 Conclusion: Despite research studies on cowpea and drought, there appears to be limited such research findings on the time to flowering, and maturity in relations to drought tolerance in cowpea in Ghana, suggesting more research in this part of the world.

Corrigendum.

[This corrects the article DOI: 10.1002/ece3.4639.].

Evaluation of the Prevalence of Congeners from Distilled Spirits of Different Sources

Aim: With recent increase in health-related incidence arising from consumption of spirit beverages in Nigeria, there is need to investigate the prevalence of possible contaminants in spirits that may have toxicological effect on human when consumed. The purpose of this study was to determine the type and levels of congeners present in spirits obtained from fermentates of cassava, molasses and palm wine purchased from different locations.
 Study Design: This study was made to fit a one way Analysis of Variance.
 Place and Duration of Study: The research was carried out at laboratory of Department of Food Science and Technology, Federal University of Technology, Owerri and Project Development Agency (PRODA) Enugu and International Institute of Tropical Agriculture (IITA), Ibadan, Oyo State, Nigeria, between April 2017 and November 2018.
 Methodology: Analysis of common congeners in spirits of cassava, molasses and palm wine fermentates obtained through distillation method was carried out using the Gas-Chromatography. Physicochemical properties of the spirits measured were specific gravity, pH and viscosity. The spirit distillates were analysed for concentrations of ethanol, higher alcohols and possible congeners such as esters, ethyl carbamate (EC) and ethyl acetate.
 Results: The distillates yielded alcoholic content of 39.00 to 46.71%. Ethyl carbamate content of spirits from cassava recorded an average mean value of 13.44 µg/l which was not significantly different from (P > .05) spirits from molasses and palm wine, with an average mean values of 12.49 µg/l and 13.75 µg/l respectively. The most important higher alcohols of the spirit distillates responsible for aromatic characteristic of spirits were found to be 1-propanol (0.06-0.11%), isobutyl alcohol (0.02-0.09%) and isoamyl alcohol (0.12-0.76%). The type and location of raw materials did not significantly affect the concentrations of the available congeners found in the distilled spirits. Good fermentation employed in this research work significantly reduced the concentrations of the detected congeners.
 Conclusion: Comparing the results with data from literature, it can be concluded that the concentrations of all investigated volatile compounds in the samples of spirits from cassava, palm wine and molasses are commonly acceptable. Federal regulatory agencies such as National Agency for Food Drug Administration and Control (NAFDAC), Standard Organization of Nigeria (SON) should be encouraged to carry out routine analysis on commonly produced and sold spirit beverages in order to prevent sale of contaminated drinks.

Crossbreeding East African Highland Bananas: Lessons Learnt Relevant to the Botany of the Crop After 21 Years of Genetic Enhancement.

East African highland bananas (EAHB) were regarded as sterile. Their screening for female fertility with “Calcutta 4” as male parent revealed that 37 EAHB were fertile. This was the foundation for the establishment of the EAHB crossbreeding programs by the International Institute of Tropical Agriculture (IITA) and the National Agricultural Research Organization (NARO) in Uganda in the mid-1990s. The aim of this study was to assess the progress and efficiency of the EAHB breeding program at IITA, Sendusu in Uganda. Data on pollinations, seeds generated and germinated, plus hybrids selected between 1995 and 2015 were analyzed. Pollination success and seed germination percentages for different cross combinations were calculated. The month of pollination did not result in significantly different (P = 0.501) pollination success. Musa acuminata subsp. malaccensis accession 250 had the highest pollination success (66.8%), followed by the cultivar “Rose” (66.6%) among the diploid males. Twenty-five EAHB out of 41 studied for female fertility produced up to 305 seeds per pollinated bunch, and were therefore deemed fertile. The percentage of seed germination varied among crosses: 26% for 2x × 4x, 23% for 2x × 2x, 11% for 3x × 2x, and 7% for 4x × 2x. Twenty-seven NARITA hybrids (mostly secondary triploids ensuing from the 4x × 2x) were selected for further evaluation in the East African region. One so far –“NARITA 7”– was officially released to farmers in Uganda. Although pollination of EAHB can be conducted throughout the year, the seed set and germination is low. Thus, further research on pollination conditions and optimization of embryo culture protocols should be done to boost seed set and embryo germination, respectively. More research in floral biology and seed germination as well as other breeding strategies are required to increase the efficiency of the EAHB breeding program.

Dennis James Greenland. 13 June 1930—23 December 2012

Dennis Greenland was an outstanding soil scientist who combined the analytical rigour of a chemist with the practical application of an agricultural scientist. His early research employed X-ray diffraction and other emerging analytical techniques to determine the surface properties of clay minerals and their interactions with organic components of soils. This, in turn, led to research to understand the forces leading to aggregate and structural stability (and instability) in soils of the UK, Australia, Nigeria and the tropics generally. Simultaneously, Dennis engaged with the practical problems faced by farmers in the tropics to maintain the fertility of their soils and ensure long-term crop production; his early work (with Peter Nye) on shifting cultivation is regarded as a classic of the soil science literature. These two elements of his research came together during his periods as deputy director general, with responsibility for research, at the International Institute for Tropical Agriculture (IITA) in Nigeria (1974–1976) and the International Rice Research Institute (IRRI) in The Philippines (1979–1987). At both institutions he sought to improve the research in natural resources so that the genetic gains delivered by crop breeding could be achieved by farmers on their fields. At IRRI he encouraged research on rice-growing environments and improved water management taking account of catchment uses, and he promoted integrated approaches to nutrient management that combined organic and inorganic sources. This passion for integrated approaches to soil management led to his championing, and eventually chairing, the International Board for Soil Research and Management (IBSRAM), in which he played a major role in forming networks of multi-location experiments with many institutions.

Proximate analysis and SDS-PAGE protein profiling of cassava leaves: utilization as leafy vegetable in Nigeria

Introduction: Cassava (Manihot esculenta Crantz) is an important starchy food crop whose leaf is yet to be adopted and utilized as leafy vegetable and as potential protein source for monogastric animals in Nigeria. Providing more nutritional information and highlighting health benefits could encourage consumption, hence this study. Methodology: Twelve varieties of cassava were collected from farmers and Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA), Ibadan, Oyo State, Nigeria. Total protein content was estimated in supernatant using BSA as standard. Moisture, dry matter, protein, crude fat, ash, sodium and potassium contents were determined using standard protocols. Results: The proximate analysis show that crude protein percentage ranged from 11.81 in variety OsNo001 to 22.75 in variety IBA30572. Moisture content varied from 8.09 in OsNo001 to 10.90 in IBA011371 while ash content varied from 6.88 in IBA010040 to 9.64 in variety 1089A. Four varieties IBA950289, IBA980505, TMEB91934 and 1089A have richer proximate content in ash, protein, carbohydrate, and fat contents. The result of SDS-PAGE indicates the presence of proteins in all the cassava leaves analyzed. The SDS-PAGE cluster analysis generated four major cluster groups suggesting the presence of four types of protein. Conclusion: The cassava leaves are comparable to known leafy vegetables Amaranthus in nutritional and biochemical contents. It is evident that the protein content might be sufficient enough to adopt cassava leaves as a leafy vegetable based on the SDS-PAGE. Thus, the cassava varieties are good candidates for utilization as leafy vegetable to augment the exotic and known leafy vegetables in Nigeria.

What impact does the adoption of drought-tolerant maize for Africa have on the yield and poverty status of farmers in the arid region of Nigeria?

Maize production in Nigeria has not been able to meet the needs of people owing to drought, low productivity and lack of access to improved varieties by the farmers. Increased agricultural yield is a potential means for increasing household income, which tends to lower the poverty status of small-holder farmers. This study assessed the impact of Drought-Tolerant Maize for Africa (DTMA) on the yield and poverty status of farmers in the northwestern region of Nigeria. The study used the dataset from Adoption of DTMA Survey by the International Institute of Tropical Agriculture (IITA), Ibadan, with 293 respondents from northwestern Nigeria (90 adopters and 203 non-adopters of DTMA). Data were analysed using descriptive statistics, binary regression and propensity score matching methods. Results showed that small-holder farmers were more likely to adopt DTMA than bigger farms. Adopters had an increase in DTMA yield of 9,262.77kg/ha while the counterfactual non-adopters had an increase of 3,807.74kg/ha. The adoption of DTMA reduced the probability of being poor by 60 percent for the treatment group while poverty incidence was reduced by 35% among the non-adopters. The general conclusion is that DTMA adoption program improved maize yield and reduced poverty incidence among rural households.

Genetic Diversity and DNA Barcoding of Yam Accessions from Southern Nigeria

Knowledge of genetic diversity and barcoding of yam is lacking in Enugu and Ebonyi States of southern Nigeria. Therefore, DNA barcoding was used to facilitate identification and biodiversity studies of yam species from Southern Nigeria. Seventy five yam accessions were collected from Enugu and Ebonyi States, including International Institute of Tropical Agriculture for DNA extraction and amplification using a chloroplast DNA (cpDNA) ribulose-1,5-bisphosphate carboxylase (rbcL) marker. There was high level of similarity among the accessions and presence of 534 conserved and 7 variable sites. A transversional mutation of G/T at a consensus position of 335 was identified followed by transitions at 362 (A/G), 368 (A/G), 371 (C/T) and 391 (C/T) within the accessions. Phylogeny resolved the yam accessions into ten major groups with their bootstrap values ranging from 0 - 100. Phylogenetic diversity was highest in group X, followed by VII, VI and IX. The inter-group genetic distance based on Kimura 2-parameter model ranged from 0.5000 ± 0.4770 - 5.0560 ± 2.5760, while the intra-group had 0.5250 ± 0.5000 - 2.0103 ± 1.2579. The mean genetic diversity within the entire population was 0.7970 ± 0.06910. BLAST analysis of total bit score, query coverage, and percentage identity were in the ranges of 411 - 1011, 99% - 100% and 97% - 100%, respectively. However, the rbcL could not resolve the yam accessions well following the comparative assessment of some discrepancies in the detected number of species from phylogenetic groupings, genetic diversity indices and NCBI BLAST hits, thereby, exposing the inefficiency of this marker in discriminating the yam accessions. It was demonstrated that rbcL is not an effective marker; therefore, it should not be recommended as a standard-alone marker of choice for DNA barcoding of yam accessions, especially, when accurate identification, discrimination and estimation of genetic diversity of this vital crop are of paramount importance for crop improvement and germplasm conservation.

Investigation on the Possibility of Using Available Sunshine Duration Data of a Relatively Close Region to Estimate Global Solar Radiation for a Different Region

Estimation of global solar radiation using existing models becomes necessary in areas where measurements are not carried outdue to lack of technical knowledge, unavailability of measuring instrument and cost of getting such measurements if available.In this study, the possibility of estimating the global solar radiation for a particular location using another location's sunshine duration data is explored due to the closeness in the latitude of the two locations and to what extent is the estimation true.  Ibadan's (latitude 7.37750N) sunshine duration data is used as Iwo's (latitude 7.62920N) sunshine duration data and employed in the Angstrom - Prescott's sunshine based model, while retaining the latitude of Iwo in the model, mean sunset/rise hour angle and extraterrestrial radiation. The sunshine duration data for Ibadan (2008 - 2012) was gotten from International Institute of Tropical Agriculture, Ibadan while the measured global solar radiation data for Iwo (2014 - 2015) was measured at Bowen University Iwo, Osun state in Nigeria. The estimated global solar radiation for Iwo is validated with measured global solar radiation at Iwo by carrying out some statistical analysis like mean bias error (-0.03), root mean square error (0.81), mean percentage error (-0.23), Nash-Sutcliffe error (r2) or coefficient of determination (0.88), coefficient of correlation (0.94). The estimated values when validated against the measured values performed excellently well. Hence it is possible to use the available sunshine duration data of another location as the sunshine duration data when estimating the global solar radiation available at the location of interest.

Field Evaluation of Yield and Yield Component Traits of Breeding Lines of Maize over Two Seasons in Derived Savannah Agro-Ecology

The understanding of yield and the interaction with its components is very important for selection in early generations of crop breeding. Twelve maize genotypes were collected from International Institute for Tropical Agriculture (IITA) along with seven landraces in order to identify the contribution of different traits to yield improvement. The experiments were carried out in two different seasons (March/April-early and July/August- late) in a randomized complete block design with three replications. Early season planting had a higher grain yield than late season planting. The difference in grain yield between early and late season was 3.92 tons/ha. This represents a 27.8% increase in grain yield during the early season over the late season planting. Number of ears per plant and shelling percentage were not influenced by seasonal effects. Ear weight and days to tasselling showed the highest direct positive effects of 0.972 and 0.665, respectively on grain yield, during early season. Furthermore, ear weight, followed by shelling percentage, exerted the highest direct positive effect on grain yield in late season. Higher indirect positive effects were obtained for ear diameter, ear length, ear height and plant height via ear weight in both seasons. Ear weight, days to tasselling and ear length were identified as the major traits affecting yield of maize in both seasons in the derived Savannah agro-ecology.

Cassava farming practices and their agricultural and environmental impacts: a systematic map protocol

BackgroundCassava (Manihot esculenta) is a staple crop that is important for food security in the tropics. However, cassava farming can have severe environmental impacts, such as habitat destruction and soil degradation, if it is not carefully managed. Therefore, a wide range of agricultural and environmental outcomes should be considered when cassava farming practices are recommended as “good agricultural practices”. We propose a systematic map of research on cassava farming practices and their impacts on yield, quality, profitability, soil, water, wildlife, pathogens, pests, weeds, and other agricultural and environmental outcomes. This map will improve our knowledge of the multifunctionality of cassava farming practices, by answering several questions: Which studies have measured the impacts of cassava farming practices on agricultural and/or environmental outcomes? Which practices and outcomes have been studied, in which countries, and when?MethodsWe will search for studies of “cassava OR mandioca OR manihot OR manioc OR yuca” in four publication databases (AGRICOLA, AGRIS, Scopus, Web of Science), two repositories of grey literature (including publications from the International Center for Tropical Agriculture and the International Institute of Tropical Agriculture, which have worked extensively on cassava), and the Conservation Evidence database. We will screen the search results using eligibility criteria that are transparently reported and consistently applied. We will not critically appraise the validity of the studies that are included in the map, because we see this map as a subject-wide evidence base that could be used for multiple methods of evidence synthesis, with different criteria for critical appraisal. We have developed a classification of agricultural practices and a classification of agri-environmental outcomes, and we will use these classifications (“taxonomies” or “terminological ontologies”) when coding studies. We have developed a web application (http://www.metadataset.com) with drop-down menus for screening and coding. We will analyse the number of studies by practice, outcome, country, and year, and we will present the results as a searchable database with interactive geographical maps (an “evidence atlas”) that will show knowledge gaps and knowledge clusters.

Influence of tillage on soil physical properties and three varieties of sesame (Sesamum indicum L.) in Ogbomoso, southwestern Nigeria

Influence of tillage on soil physical properties and three varieties of sesame (Sesamum indicum L.) in Ogbomoso, southwestern Nigeria

Influence of Rhizobium Inoculation on Nodulation, Biomass Production and Yield of Some Indigenous Legumes in the Rainforest Agro-Ecological Zone of Nigeria

A field study was conducted during the late cropping seasons of 2015 and 2016 at Akamkpa (latitude 5°15' N and longitude 8°22'E), southern Nigeria, to evaluate the response of some legume genotypes to seed inoculation with NoduMax, a Rhizobium inoculant developed by the International Institute of Tropical Agriculture (IITA). Treatments were factorial combinations of inoculated and non-inoculated seeds of Cowpea, Groundnut, Bambara groundnut, Bebi (Viny Lima) bean, Mucuna bean, and African yam bean, laid out in randomized complete block design replicated thrice. The response of the test crops to inoculation varied with growth stage. At the seedling stage, effective nodule number was not significantly affected in all but Mucuna bean in which there was a 42.7% reduction. At pre-an thesis, Bambara groundnut, Bebi bean, Groundnut, and Cowpea recorded a statistically similar number of nodules(p=0.05) under inoculated and non-inoculated conditions, but inoculation reduced nodule formation in Mucuna bean and African yam bean by 22.4 and 20.4%, respectively. Nodule dry weight of Bebi bean, Bambara groundnut, Mucuna bean and Cowpea was unaffected by inoculation when assessed at the seedling and pre-anthesis growth stages, but that of Groundnut was reduced by 35, and African yam bean increased by 60%, respectively. Inoculation increased the nodule dry weight of African yam bean and Mucuna bean by 56.5 and 60.6% at seed initiation stage, and reduced that of Bambara groundnut and Groundnut by 25.6 and 50.0%, respectively. The effect of genotype í— inoculation interaction on plant biomass and fresh grain yield was significant; whereas inoculation significantly increased the yield of Cowpea from 2,471 to 2,794 kg/ha and 2,995 to 3504 kg/ha in 2015 and 2016, respectively, it did not significantly affect that of Bebi bean, African yam bean and Bambara groundnut. On the contrary, the yield of groundnut was reduced from 884 to 560 kg/ha and 963 to 678 kg/ha in 2015 and 2016, respectively. Inoculation with NoduMax was beneficial to cowpea, but did not significantly improve the performance of Bebi bean, and Groundnut. It could be that Bebi bean is promiscuous and better adapted to the native strains of Rhizobium, while the Rhizobium in Groundnut is antagonistic and incompatible with the introduced inoculants. Binang et al.; JALSI, 11(4): 1-9, 2017; Articleno.JALSI.32624 2 recorded a statistically similar number of nodules (p=0.05) under inoculated and non-inoculated conditions, but inoculation reduced nodule formation in Mucuna bean and African yam bean by 22.4 and 20.4%, respectively. Nodule dry weight of Bebi bean, Bambara groundnut, Mucuna bean and Cowpea was unaffected by inoculation when assessed at the seedling and pre-anthesis growth stages, but that of Groundnut was reduced by 35, and African yam bean increased by 60%, respectively. Inoculation increased the nodule dry weight of African yam bean and Mucuna bean by 56.5 and 60.6% at seed initiation stage, and reduced that of Bambara groundnut and Groundnut by 25.6 and 50.0%, respectively. The effect of genotype í— inoculation interaction on plant biomass and fresh grain yield was significant; whereas inoculation significantly increased the yield of Cowpea from 2,471 to 2,794 kg/ha and 2,995 to 3504 kg/ha in 2015 and 2016, respectively, it did not significantly affect that of Bebi bean, African yam bean and Bambara groundnut. On the contrary, the yield of groundnut was reduced from 884 to 560 kg/ha and 963 to 678 kg/ha in 2015 and 2016, respectively. Inoculation with NoduMax was beneficial to cowpea, but did not significantly improve the performance of Bebi bean, and Groundnut. It could be that Bebi bean is promiscuous and better adapted to the native strains of Rhizobium, while the Rhizobium in Groundnut is antagonistic and incompatible with the introduced inoculants.

Genetic diversity and population structure of a mini-core subset from the world cowpea (Vigna unguiculata (L.) Walp.) germplasm collection

The International Institute of Tropical Agriculture maintains the world’s largest collection of cowpea germplasm of over 15,000 accessions. A sub-set of 298 lines from the loosely composed mini core collection of 370 landraces were genotyped based on genotyping by sequencing (GBS). Ward’s minimum variance hierarchical cluster analysis, model-based ancestry analysis and discriminant analysis of principal component (DAPC) were carried out on this sub-set. Three clusters were identified by the different clustering methods. Principal component analysis further supported the three clusters especially when accessions are scattered along the axes of the first two principal components. The first two principal components explained a total of 22.30% of the variation. Cluster one comprises 115 accessions from the largest number of countries and has the highest gene diversity, heterozygosity and polymorphic information content (PIC) values. Cluster two is made up of 102 accessions, 90 percent of which are from West and Central Africa. Analysis of molecular variance shows that the most variation is among accessions and lowest among clusters. No cluster is made exclusively of accessions from a single country. Based on SNP markers, the sub set of cowpea mini core germplasm collection used in this study encompasses the diversity in the crop.

Evaluation of cowpea (Vigna unguiculata (L.) Walp.) landraces to bacterial blight caused by Xanthomonas axonopodis pv. vignicola

Cowpea is an important protein source for human populations in many nations across sub-Saharan Africa (SSA). However, cowpea production is constrained by bacterial blight (CoBB) caused by Xanthomonas axonopodis pv. vignicola (Xav), a disease affecting most cowpea-growing areas. A large proportion of smallholder farmers across SSA rely on traditional cowpea landraces (CLR) to produce the crop. The International Institute of Tropical Agriculture (IITA) possesses the largest collection of cowpea germplasm, including several CLR accessions. However, screening for resistance to CoBB in most of the CLR accessions maintained at IITA has not been conducted. CoBB severity was evaluated in 103 CLR accessions from five African countries, the US, The Philippines, and Sri Lanka by artificially inoculating a highly virulent Xav strain in plants grown in a screenhouse. Highly significant (P < 0.0001) differences in susceptibilities to the disease were detected among the evaluated germplasm. Resistance was detected in several CLR accessions with two accessions from Nigeria and one from the US developing no disease symptoms. Our results indicate that several CLR accessions are valuable sources of resistance to CoBB and those could be used to breed for improved varieties with superior resistance to the disease. The resistant CLR accessions and others in IITA collection should be further investigated to identify additional beneficial traits that may contribute to the development of improved, commercially acceptable varieties.

“Estimating the Productivity Impacts of Technology Adoption in the Presence of Misclassification”—Author Response to Comment

American Journal of Agricultural EconomicsVolume 101, Issue 1 p. 19-19 Lead Article with Discussion and Response “Estimating the Productivity Impacts of Technology Adoption in the Presence of Misclassification”—Author Response to Comment Tesfamicheal Wossen, Tesfamicheal Wossen Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this authorTahirou Abdoulaye, Tahirou Abdoulaye Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this authorArega Alene, Arega Alene Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this authorPierre Nguimkeu, Pierre Nguimkeu Assistant Professor Department of Economics, Georgia State UniversitySearch for more papers by this authorShiferaw Feleke, Shiferaw Feleke Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this authorIsmail Y. Rabbi, Ismail Y. Rabbi Molecular Geneticist/Breeder IITASearch for more papers by this authorMekbib G. Haile, Mekbib G. Haile World BankSearch for more papers by this authorVictor M. Manyong, Victor M. Manyong Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this author Tesfamicheal Wossen, Tesfamicheal Wossen Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this authorTahirou Abdoulaye, Tahirou Abdoulaye Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this authorArega Alene, Arega Alene Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this authorPierre Nguimkeu, Pierre Nguimkeu Assistant Professor Department of Economics, Georgia State UniversitySearch for more papers by this authorShiferaw Feleke, Shiferaw Feleke Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this authorIsmail Y. Rabbi, Ismail Y. Rabbi Molecular Geneticist/Breeder IITASearch for more papers by this authorMekbib G. Haile, Mekbib G. Haile World BankSearch for more papers by this authorVictor M. Manyong, Victor M. Manyong Economist International Institute of Tropical Agriculture (IITA)Search for more papers by this author First published: 15 October 2018 https://doi.org/10.1093/ajae/aay079 This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume101, Issue1January 2019Pages 19-19 RelatedInformation

Combining Ability and Heterosis of Tolerance to Low Soil Nitrogen in Tropical Maize Cultivars Derived from Two Breeding Eras

Abstract Low soil nitrogen is one of the principal abiotic stresses affecting maize productivity in Sub-saharan Africa. Field studies were conducted at the International Institute of Tropical Agriculture (IITA), Ibadan during the cropping seasons for three years, from 2010 to 2012, with ten open pollinated maize varieties (OPVs) derived from two breeding eras (1 and 2). The ten OPVs and their crosses were evaluated under high-N and low-N conditions. The aim was to identify superior populations that may be useful sources genes for inbred line extraction and hybrid development for grain yield. Under low-N condition, mid and high parent heterosis for grain yield were low indicating the suitability of the hybrids for cultivation only in environments with high productivity index. Hybrid DMR-LSR-W (Era 1) × TZSR-Y-I (Era 2) had greatest mid and high-parent heterosis for grain yield under high-N and across the other four test environments. Parent AMATZBR-WC2B with higher general combining ability effects and mean values for grain yield, and cross combinations DMR-LSR-W (Era 1) x BR9928DMRSR (Era 2) and BR9922DMRSR (Era 2) x TZBRELD-4C0W (Era 2) with higher specific combining ability for grain yield under low-N environment are promising candidates for the development of nitrogen use efficient varieties for cultivation in low-N environments.

English

Lepidopteran borers are the most devastating field pests of maize in West and Central Africa. In view of the rapidly changing climate which favours an upsurge of more destructive biotypes of insect pests, diverse sources of resistance from different genetic backgrounds need to be harnessed for crop improvement purposes. Forty tropical maize inbreds comprising adapted and exotic lines from International Institute of Tropical Agriculture (IITA) and International Maize and Wheat Improvement Centre (CIMMYT) maize breeding programs were evaluated for resistance to two species of stem borers- Sesamia calamistis and Eldana saccharina at Ibadan and Ikenne, Nigeria, under artificial infested and non-infested conditions in 2015 and 2016 cropping seasons. The experiment was laid out in a randomized complete block design in three replicates. Data were collected on agronomic traits and stem borer damage parameters. On average, the CML lines had relatively higher grain yield despite the high level of stem tunneling, stalk breakage and cob damage, with the exception of CML 67 (0.19 ton/ha) and CML 71 (0.06 tons/ha). BD 74-395 had the highest yield (1.45 t/ha) among the BDs, despite its high stalk breakage and cob damage. Among IITA lines, KU1414SR/SR, 1368 and 9030STR were the highest yielding with grain yields of 1.71, 1.39 and 1.19 t/ha, respectively. Moderate to high heritability was observed among the stem borer damage parameters. Negative genetic gain was observed in stem tunneling. Mean square of lines was significant for all the traits studied. The top-performing inbreds were similarly grouped using the rank summation index and principal component analysis. The exotic lines had good adaptability and showed potential as sources of stem borer resistance, and could therefore be explored in breeding programs for resistance to Eldana and Sesamia. Key words: Eldana saccharina, maize inbreds, resistance, Sesamia calamistis, tropics. &nbsp

Assessment of genetic diversity in plantain (&lt;i&gt;Musa paradisiaca&lt;/i&gt; L.) using RAPD marker

Insufficient information on the diversity of plantain and its relationship with other Musa species in the Musa genus has been cited as one of the major problems hindering genetic improvement within the genus. Hence, this study aimed to assess genetic diversity among plantain cultivars using RAPD markers. Fifteen plantain cultivars were deployed for this study, comprising of ten landraces sourced from different parts of Edo state and five hybrids from International Institute of Tropical Agriculture (IITA), Ibadan. The study revealed a total number of 2 alleles across 4 RAPD primers analysed, effective number of alleles (N e ) ranged from 1.14-2.0, Nei's genetic distance (H) had a mean of 0.30. Polymorphic information content (PIC) ranged from 0.12 (OPT-07) to 0.23 (OPH-06), 0.40 (OPT-01) and 0.46 (OPT-06), with a mean of 0.30, which indicated that markers used were polymorphic. Dendrogram revealed 2 clusters; MP EKO and MP ACH both from Edo state displayed genetic relatedness and were more related to MP No. 2 from IITA than MP 07 FPT in the same cluster. The results suggest that though the hybrids have been improved for special qualities, the landraces from Edo state could possess some genes of interest in plantain breeding program. Keywords: Musa paradisiaca , RAPD, genetic variability, markers