International Institute Of Tropical Agriculture Research Articles

The pattern of genetic variability in a core collection of 2,021 cowpea accessions.

Cowpea is a highly drought-adapted leguminous crop with great promise for improving agricultural sustainability and food security. Here, we report analyses derived from array-based genotyping of 2,021 accessions constituting a core subset of the world's largest cowpea collection, held at the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria. We used this dataset to examine genetic variation and population structure in worldwide cowpea. We confirm that the primary pattern of population structure is two geographically defined subpopulations originating in West and East Africa, respectively, and that population structure is associated with shifts in phenotypic distribution. Furthermore, we establish the cowpea core collection as a resource for genome-wide association studies by mapping the genetic basis of several phenotypes, with a focus on seed coat pigmentation patterning and color. We anticipate that the genotyped IITA Cowpea Core Collection will serve as a powerful tool for mapping complex traits, facilitating the acceleration of breeding programs to enhance the resilience of this crop in the face of rapid global climate change.

Serological and RT-PCR evaluation of African yam bean (Sphenostylis stenocarpa (Hochst ex. A. Rich) Harms) accessions to viral resistance under field condition

African yam bean (AYB) (Sphenostylis stenocarpa (Hochst ex. A. Rich.) harms) an underutilized legume that produces nutritionally healthy seeds and tubers in some variety. The low yield of the crop is attributed to production constraints such as attacks by pest and disease-causing organisms such as fungi, bacteria and viruses. In this study, one hundred AYB accessions were evaluated for resistance to viral infection. The AYB accessions were planted using a randomized complete block design on the experimental field at the International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria. Viral disease severity was assessed at 10, 12, 14, 16 and 18 weeks after planting (WAP) based on disease symptoms using disease severity index on visual scale of 1–5. Antigen–coated plate enzyme linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction were used to index diseased leaf samples collected from the field. Result from five virus species (Cowpea mild mottle virus, Cowpea mottle virus, Southern bean mosaic virus, Cowpea mosaic virus and Bean common mosaic virus) were detected in few accessions while mixed infections were observed in some accessions. TSs-552, TSs-577, TSs-580, TSs-560 and TSs-600 were devoid of viruses and could be resistant. There were no significant differences at p < 0.05 in the mean disease incidence (DI) of viral diseases. However, at 18 weeks after planting, TSs-604 had the highest (100%) mean DI while TSs-584 had the lowest (13.33%) mean DI. Cluster analysis based on the AUDPC produced 6 main clusters, the clusters revealed grouping patterns in which AYB lines with similar resistance ratings were shown to form unique clusters. The information generated from this study will contribute to the development of strategies in the management of virus diseases infecting AYB.

Assessment of levels of selected macro and microelements present in biofortified provitamin-A cassava varieties

Biofortification of cassava varieties has become a common means of improving essential elements to boost food quality. This study investigated the amount of macro and microelements present in some vitamin A-fortified cassava varieties developed by cassava breeders at the International Institute of Tropical Agriculture (IITA) Ibadan. The roots of three pro-vitamin fortified cassava varieties IBA154800, IBA164785 and IBA164791 growing at the field of the IITA cassava breeding unit were harvested and were profiled for the macro and microelement using a Tecator digester and AAS. The Mg, Zn, Cu, K, Fe and Na contents were read in triplicates. Data collected were analysed using ANOVA and correlation (SAS 9.4 version) and the differences in the varietal means were separated using the least significant differences at a 5% level of significance. The macro elements Mg, K, and Na differed significantly across the varieties and ranged from 0.114 (IBA164791) to 0.143 (IBA164785), 1.463 (IBA164791) to 2.147 (IBA164785), and 29.138 (IBA164785) to 37.433 (IBA154800), respectively. The microelements Fe, Cu and Zn also differed significantly amongst the varieties and ranged from 19.021 (IBA164791) to 29.874 (IBA164785), 1.463 (IBA164791) to 2.147 (IBA164785), and 29.138 (IBA164791) to 37.433 (IBA154800), respectively. The relationship between Zn and Fe (-0.88), and between Na and Cu (-0.85) were significantly strong and negative. The relationship between Fe and Mg (0.89), Mg and Cu (0.85), and Mg and K (0.71) were significantly strong and positive. The biofortified variety IBA164785 had a higher improvement rate in the macro and microelements investigated.   

Assessing the Potential of Extra-Early Maturing Multiple Stress-tolerant Maize Hybrids Under Different Rates of Nitrogen

Decline in soil fertility is a major constraint to maize production. This study aimed to assess the agronomic performance of improved maize varieties under different nitrogen rates to identify low nitrogen tolerant varieties. Five multiple stress-tolerant maize hybrids, developed by maize improvement program of the International Institute of Tropical Agriculture (IITA), and an open-pollinated variety used as check were evaluated under three levels nitrogen at two locations during 2019 growing season. The experiment was laid out in a split-plot experiment with three replications at each location. Nitrogen rates and varieties were the main and secondary factors, respectively. Data collected on grain yield and its related traits and were subjected to analysis of variance at 5% level of significance. The average grain yield of the six varieties under different nitrogen levels ranged from 2.2 t/ha at 0 kgN/ha in Angaradébou to 5.3 t/ha at 76 kgN/ha in Komkoma. Hybrid TZEEQI 342 × TZEEQI 7 showed high grain yield (4.0 t/ha) across the two agro-ecologies while varieties TZEE-W Pop STR QPM Co × TZEEQI 7 (3.7 t/ha) and TZdEEI 91 × TZEEI 21 (3.6 t/ha) had comparable grain yield. These hybrids were also less susceptible to nitrogen stress. They are the promising genotypes for Angaradébou localities while farmers around Komkoma should continue to cultivate TZEE-W Pop DT STR QPM.

Approaches and progress in breeding drought-tolerant maize hybrids for tropical lowlands in west and central Africa.

Drought represents a significant production challenge to maize farmers in West and Central Africa, causing substantial economic losses. Breeders at the International Institute of Tropical Agriculture have therefore been developing drought-tolerant maize varieties to attain high grain yields in rainfed maize production zones. The present review provides a historical overview of the approaches used and progress made in developing drought-tolerant hybrids over the years. Breeders made a shift from a wide area testing approach, to the use of managed screening sites, to precisely control the intensity, and timing of drought stress for developing drought-tolerant maize varieties. These sites coupled with the use of molecular markers allowed choosing suitable donors with drought-adaptive alleles for integration into existing elite maize lines to generate new drought-tolerant inbred lines. These elite maize inbred lines have then been used to develop hybrids with enhanced tolerance to drought. Genetic gains estimates were made using performance data of drought-tolerant maize hybrids evaluated in regional trials for 11 years under managed drought stress, well-watered conditions, and across diverse rainfed environments. The results found significant linear annual yield gains of 32.72kg ha-1 under managed drought stress, 38.29kg ha-1 under well-watered conditions, and 66.57kg ha-1 across multiple rainfed field environments. Promising hybrids that deliver high grain yields were also identified for areas affected by drought and variable rainfed growing conditions. The significant genetic correlations found among the three growing conditions highlight the potential to exploit the available genetic resources and modern tools to further enhance tolerance to drought in hybrids.

Performance Evaluation of Four Novel Cassava (Manihot esculenta Crantz) Accessions to Different Fertilizer Types in Awka, Anambra State, Nigeria

The investigation was carried out on the effects of fertilizer and cassava variety on agronomic characteristics, yield, and disease incidence of four improved cassava accessions. The experiment was carried out at the Teaching and Research farm of Crop Science and Horticulture, Nnamdi Azikiwe University Awka, Anambra State. It was a 4 × 3 factorial experiment with treatments laid out in a Randomized Complete Block Design (RCBD) with three replications. Fertilizer types were NPK 15:15:15 at a rate of 400 kg/ha, poultry manure (PM) at a rate of 50 tons/ha and no application as control. The cassava accessions were TMS539, TMS092, TMS371 and TMS412, obtained from the International Institute for Tropical Agriculture (IITA) in Ibadan, Nigeria. Stems were cut to about 15cm and planted at a spacing of 0.5m apart. The parameters measured were the number of root tubers, total number of rot tubers, weight of tuber (kg), stem girth (cm), node per stand, branching interval, internode spacing (cm), number of branching, plant height (cm), age at branching, disease incidence. Normal agronomic practices were carried out. Results showed that all varieties responded to the application of inorganic and organic fertilizers. Cassava plants that did not receive any fertilizer application (no application) gave the highest number of root tubers (29.7) from TMS412, and the least was from TMS092. The result also showed that there was no significant difference in the effects of fertilizer type on diseases. Results also showed that there was a significant interactive effect of cassava varieties and fertilizer type on branching interval (7.009), Internode spacing (0.6195), number of branching (0.2822), and plant height (17.02) at six months after planting. From the investigation, it could be recommended that for farmers to obtain greater yields with little or no fertilizer application, these cassava accessions should be used, which are characterized by high yield and resistance to disease and pests, as shown from this research.

Evaluating breeding for broad versus narrow adaptation for cassava in Nigeria using stochastic simulation

AbstractThe cassava (Manihot esculenta Crantz) breeding program at the International Institute of Tropical Agriculture (IITA) has adopted genomic selection to accelerate genetic gain. The program continues to develop varieties broadly adapted across Nigeria's diverse agroclimatic zones. However, for this purpose, genotype‐by‐environment interaction (GEI) presents a challenge. To decide whether broad adaptation breeding is a good strategy, we evaluated broad versus narrow adaptation strategies using stochastic simulation, assessing genetic gain, genetic variance, heritability, and selection accuracy at 0 versus realistic levels of GEI variance. To parameterize the models, we analyzed historical data from four phenotypic evaluation stages of the IITA breeding program to estimate genetic and error variances, and genetic correlations across environments. Based on these observed parameters, the genomic‐enabled breeding programs exhibited higher genetic gain than the conventional program for both GEI variances. At realistic GEI variance, the narrow adaptation program showed higher genetic gain than the broad adaptation program. Across all programs, the genetic variance declined over time, though the genomic‐enabled programs showed higher initial variance due to the selection of parents at earlier stages. At realistic GEI variance, an increase in genetic variance was observed in the narrow adaptation program due to its conversion of GEI between mega‐environments into main genetic variance within mega‐environments. This higher genetic variance led to higher heritabilities and selection accuracies. This study highlights the potential of genomic selection in accelerating genetic gain and suggests that dividing the IITA cassava breeding program to target more than one mega‐environment should be considered.

Influence of temperature regimes on drought stress tolerance of cowpea genotypes in Northern Guinea savannah, Nigeria

Drought is a major constraint that affects cowpea production in Zaria, Nigeria. It is unpredictable, and occurs at any growth stage of cowpea. Changes in global climatic trendsare consistently narrowing the cowpea growing season in Northern Nigeria by graduallypushing its cultivation towards drought-prone, colder temperatures. The study aimed to elucidate foresight data on the tolerance of cowpea landraces to drought at cold and hottemperatures in a bid to harness available germplasm towards mitigating climatic changes.Seedling drought tolerance of four hundred and twenty-two (422) cowpea genotypes obtainedfrom farmers’ collection (308) and the International Institute of Tropical Agriculture (IITA) (114) was evaluated by adopting the wooden box method. The parameters evaluated were number of plants, plant height, number of trifoliate, leaf senescence, stem greenness, and recovery. The mean square values for all evaluated traits were significant (p ≤ 0.05). Leaf senescence progressed rapidly in cooler temperatures (6 oC - 18 oC). Interestingly, the recovery rate upon reintroduction of water after drought stress was higher in cold temperatures. The percentage recovery and stem greenness of drought-tolerant plants were positively associated with hot temperatures (22 oC - 36 oC). As cowpea production is pushed into colder planting season, the resilience shown by cowpea landraces in northern Nigeria are positive.

Variation in seed protein, selected minerals, phytic acid, and potential mineral bioavailability of cowpea [Vigna unguiculata (L.) Walp] mutants and accessions

AbstractCowpea [Vigna unguiculata (L.) Walp] has the potential to contribute to the eradication of hunger and malnutrition. The study objectives were to evaluate the variability of cowpea mutants; International Institute of Tropical Agriculture (IITA) and South African genotypes for protein content, selected minerals, phytic acid, and the bioavailability of iron (Fe) and zinc (Zn); to identify superior cowpea mutants, IITA, and South African genotypes; and to determine the correlation between measured characteristics. A total of 31 cowpea genotypes were planted at five different environments in South Africa. Significant (p ≤ 0.05) genotype and genotype by environment interaction effects were observed for protein, minerals, and phytic acid concentration. High broad‐sense heritability (&gt;50%) was observed for almost all the characteristics. Thirteen Namibian mutants, five IITA genotypes, and six South African genotypes that combined high protein, Fe, and Zn were identified. The IITA genotype IT93K‐452‐1 and South African genotypes Oloyin and Orelu had good Fe bioavailability. Nine Namibian mutants, four IITA genotypes, and three South African genotypes were associated with high values for protein, manganese, phytic acid, molar ratios of phytic acid with Fe and Zn, and ash. The identified superior cowpea mutants, IITA and South African genotypes could be a good source of the essential minerals and should be further studied for adaptability in South African agroecologies.

Yield Attributes and Biochemical Compositions of Elites and Landraces of Pigeon Pea [Cajanus cajan (L.) Millsp]

Pigeon pea (Cajanus cajan L. Millsp.) is an important grain legume grown mostly in the tropical regions of the world, Nigeria inclusive. The crop is still underutilised in Nigeria; the potentials of the crop in terms of yield traits and biochemical compositions, with ability of enhancing food security and preventing over-dependent on very expensive animal protein, is yet to be fully exploited. It was based on this premise that this study was designed. A total of twenty-five accessions were obtained from International Institute of Tropical Agriculture, lbadan; National Centre for Genetic Resources and Biotechnology, Ibadan and Local farmers in Oyo state, Nigeria. The seeds of the accession were sown in the field in a Randomised Complete Block Design (RCBD) with three replicates. Standard procedures were followed for determination of yield parameters as well as biochemical compositions. It showed that NG/SA/11/08/108 produced the highest grain yield (437.00). Similarly, TCC-8126 produced the highest crude protein (22.53 %) while PG/OY/18/002 had the highest carbohydrate contents (52.22 %). TCC-8126 was the best elite genotype in terms of amino acid profile, containing glutamic acid (18.10 %), aspartic acid (11.4 %); arginine (7.41 %), alanine (5.90 %). The values produced for both nutritional compositions and amino acid profiles were within the recommended standard limits set by Food and Agriculture Organisation and United States Department of Agriculture. NG/SA/11/08/108, NG/AO/MAY/09/021/02, TCC-151, TCC-8126, TT-8129 and TCC-2 have been selected as promising genotypes that could serve as breeding lines for future breeding programme of Cajanus cajan in Nigeria.

Foliar Morphological and Micromorphological Variation of Dioscorea Species in Terengganu, Malaysia

Dioscorea species are recognised for their production of tuberous roots and are referred to as "ubi" by the local population in Malaysia. The tubers of Dioscorea are commonly consumed by individuals residing in the East Coast region of Peninsular Malaysia as their primary food source. These tuberous roots are particularly abundant during the monsoon season, typically observed in local markets from October to December. Due to the availability and potential of this Dioscorea species, a study about the variation in morphological and micromorphological study of the leaves of three species of Dioscorea in Terengganu was conducted in order to identify the variation in their morphological and micromorphological characteristics. The selected species are D. esculenta (ubi itik), D. alata (ubi besar), and D. hispida (ubi gadong). The collection has been done in the Kuala Berang Terengganu area. The leaves morphological characteristics such as leaf colour, leaf type, leaf shape, leaf size, leaf margin and hairiness of adaxial and abaxial surface and shape of leaves and petiole were recorded. The morphological descriptors were suggested by the International Plant Genetic Resources Institute (IPGRI) / International Institute of Tropical Agriculture (IITA). The foliar anatomical studies of selected Dioscorea were followed by the standard tissue sectioning procedures and the observation was done by using light microscopy. The morphological study shows the variations in leaf shape, leaf base, and leaf size but they have the similarity in term of leaf margin shape and leaf attachment which is all species are petiolate. The micromorphological study shows the presence of non-glandular and uniseriate trichomes which is only obtained in the D. esculenta and D. hispida. Hence, this study contributes to the information on these species, especially for classification and identification of Dioscorea species.Keywords: Dioscorea, morphology, foliar anatomy

GROWTH AND YIELD PERFORMANCE OF TWO ACCESSIONS OF SOME LEGUMES ON EXPOSURE TO HEAVY METAL IN LAFIA NASARAWA STATE

The aim of the research was to determine the growth and yield performance of some legumes upon exposure to heavy metals.  seeds were collected from International Institute for Tropical Agriculture (IITA). Wild beans included TVNU2 and TVUN16, Cowpea: TVU2 and TVU8 while Bambara: TVSU3 and TVSU7. Dried soil collected was filled into 24 plastic buckets. Four (4) grams of lead chloride was measured with the aid of weighing balance and was dissolved into 1 litter of distilled water. Another portion of distilled water without any additive was measured and used as control. The lead solution was used to pollute the soil and allowed to stay for 24hrs before planting in a screen house. 4g of heavy metal was introduced into 8kg of soil in a bucket with each of the legumes having three replicates and was laid in a Randomized Complete Bock Design. The data collected was analyzed using two way (ANOVA) and treatment means were separated by means of LSD where differences exist. At 14 weeks after planting, results revealed that among the Cowpea accessions, TVU8 performed better than the other accession in all the parameters measured. Among the Wild bean, TVNU2 did better in most of the parameters except number leaf and number of pod/plant while in Bambara groundnut, TVSU7 performed best generally.

Morphological characterization of selected cowpea [&lt;i&gt;Vigna unguiculata&lt;/i&gt; (L.) Walp.] accessions from International Institute of Tropical Agriculture, Ibadan, Nigeria

Characterization of available germplasm is a necessary step to facilitate breeding programs worldwide. Therefore, this study aimed to characterize twenty accessions of Cowpea from the International Institute of Tropical Agriculture, Nigeria. The accessions were planted in a randomized complete block design with three replicates. The morphological characters of seedlings were assessed following the International Board for Plant Genetic Resource cowpea descriptor list (IBPGR) and twenty-nine descriptors were used. Eighteen accessions showed semi-erect habits while two showed erect plant growth habits. The number of Days to first flowering among the selected accessions was 35-45 while the number of days to first pod was 37-47. Peduncle length was observed to be 12-35 cm, Pod length was 10.61-22.81 cm while seed length was 6.10-9.93 cm among sampled accessions. Morphological assessment of the accessions showed a dendogram of three clusters with six (A), nine (B) and four (C) accessions respectively. One accession TVu-12501 formed an outgroup owing to the uniqueness of its terminal petiole length. The cluster analysis substantiated the existence of diversity among the twenty accessions for the morphological traits studied and posits TVu-12501 accession as a morphologically superior accession to be studied further for selection in breeding programmes in the West African region.

Genetic diversity and population structure of maize inbred lines using phenotypic traits and single nucleotide polymorphism (SNP) markers

Understanding germplasm’s genetic diversity is essential for developing new and improved cultivars with stable yields under diverse environments. The objective of this study was to determine the genetic diversity and population structure of 128 maize inbred lines sourced from the International Institute of Tropical Agriculture (IITA), the International Maize and Wheat Improvement Centre (CIMMYT), and the University of KwaZulu-Natal (UKZN) using 11,450 informative single nucleotide polymorphism (SNP) markers. The inbred lines revealed highly significant (p < 0.001) levels of variability for the key phenotypic traits. The SNP markers had a mean gene diversity (GD) and polymorphic information content (PIC) of 0.40 and 0.31, respectively, indicating the existence of substantial genetic variation across the germplasm panel. The model-based population structure analysis identified three subpopulations (K = 3) among the inbred lines. This corroborated the phylogenetic analysis using phenotypic traits and molecular markers which classified the inbred lines into three groups. The findings of this study identified considerable genetic diversity for the selection of inbred lines with favourable alleles for multiple traits and could be useful to initiate marker-assisted selection (MAS) to identify significant loci associated with agronomic performance and multiple-stress tolerance.

Heterotic grouping of provitamin A-enriched maize inbred lines for increased provitamin A content in hybrids

BackgroundThe establishment of heterotic groups of inbred lines is crucial for hybrid maize breeding programs. Currently, there is no information on the heterotic patterns of the Provitamin A (PVA) inbred lines developed in the maize improvement program of the International Institute of Tropical Agriculture (IITA) to form productive PVA enriched hybrids for areas affected by vitamin A deficiency. This study assessed the feasibility of classifying PVA-enriched inbred lines into heterotic groups based on PVA content without compromising grain yield in hybrids. Sixty PVA inbred lines were crossed to two testers representing two existing heterotic groups. The resulting 120 testcrosses hybrids were evaluated for two years at four locations in Nigeria.ResultsThe two testers effectively classified the inbred lines into two heterotic groups. The PVA-based general combining ability and specific combining ability (HSGCA) method assigned 31 and 27 PVA enriched maize inbred lines into HGB and HGA, respectively, leaving two inbred lines not assigned to any group. The yield-based HSGCA method classified 32 inbred lines into HGB and 28 inbred lines into HGA. Both PVA and yield-based heterotic grouping methods assigned more than 40% of the inbred lines into the same heterotic groups. Even though both PVA and yield-based heterotic grouping of the inbred lines differed from the clusters defined by the DArTag SNP markers, more than 40% of the inbred lines assigned to HGA were present in Cluster-1 and 60% of the inbred lines assigned to HGB were present in Cluster-3. Interestingly, the inbred lines assigned to the same heterotic groups based on PVA content and grain yield were distributed across the three Ward’s clusters. The PVA-based HSGCA was identified as the most effective heterotic grouping method for breeding programs working on PVA biofortification.ConclusionsSelecting PVA enriched maize inbred lines with diverse genetic backgrounds from the three marker-based clusters may facilitate the development of productive hybrids with high PVA content and for generating source populations to develop more vigorous maize inbred lines with much higher concentrations of PVA.

Impact of nitrogen-fixation bacteria on nitrogen-fixation efficiency of Bambara groundnut [Vigna subterranea (L) Verdc] genotypes.

Nitrogen fixation by bacteria is essential for sustaining the growth, development, and yield of legumes. Pot experiments were carried out at the International Institute of Tropical Agriculture (IITA) in the glasshouse between August to December 2018/2019 cropping season in Ibadan, Nigeria. Field studies were also performed in two different agroecological zones, "Ibadan and Ikenne" between August and December of 2019/2020 cropping season. The studies were set up to determine the potential of nitrogen-fixation bacteria strain inoculation on the nitrogen-fixation potential of 10 Bambara groundnut (BGN) genotypes, namely, TVSu-378, TVSu-506, TVSu-787, TVSu-1,606, TVSu-1,698, TVSu-1739, TVSu-710, TVSu-365, TVSu-475, and TVSu-305. The strains were inoculated as a broth to seedlings of each BGN genotype in the pot experiment. While six seeds from each BGN genotype were coated with each of the following nitrogen-fixation bacteria (Bradyrhizobium japonicum strains), FA3, USDA110, IRJ2180A, and RACA6, nitrogen fertilizer (urea, 20 kg/ha) was applied as a check to the nitrogen-fixation bacteria to seedlings of BGN genotypes 2 weeks after planting in both glasshouses and fields. Uninoculated plants served as controls (zero inoculation and zero fertilization). The field experiments were arranged in Randomized Complete Block Design (RCBD), while the glasshouse experiments were arranged in Complete Randomized Design (CRD) in triplicate. The result gotten showed that higher nodule numbers and weight were recorded in TVSu-1739 and TVSu-475 in both locations and seasons compared to other genotypes; the highest nitrogen fixed values were recorded among BGN genotypes TVSu-1739, TVSu-1,698, TVSu-787, TVSu-365, TVSu-305, TVSu-710, and TVSu-1,606, with a range of (62-67 kg ha-1), and were mostly enhanced by RACA6 and USDA110 strains compared to other strains that were used.

Phenotypic diversity among cowpea mutants and accessions for grain yield and yield components

Phenotypic characterization of cowpea germplasm collections is an essential step for the cowpea genetic improvement. The objectives of the study were to determine the phenotypic diversity and characterize cowpea mutants and accessions for grain yield and yield components, to identify their superiority, and to determine the correlation between measured characteristics. Thirty-one cowpea genotypes (16 Namibian mutants, seven International Institute of Tropical Agriculture (IITA) genotypes and eight South Africa genotypes) were planted in five different environments in South Africa during the 2021/2022 cropping season. Significant (P ≤ 0.05) genotype, environment and genotype by environment interaction effects were observed for all grain yield and yield components. Moderate to high broad-sense heritability (H2) (> 50%) was observed for all yield components. Superior Namibian Mutants (ShR10P12, ShR3P4, ShR4P1 and BrR11P2), IITA genotype (98K-476-8) and South African genotype (Enchore) were identified for grain yield (GY), number of seeds per plant (NSPPx), pod weight per plant (PWP) and number of pods per plant (NPP). There were significant positive correlations between most of the yield components. In the principal component analysis, Namibian mutant genotypes ShL2P7, ShR4P1, NKR1P3 and BrR11P2 were associated with high NSPPx, PWP and GY. The clustered heat map identified a group of Namibian mutants (NKR1P3, BrR11P2, ShL2P7, ShR2P11 and ShR10P12), IITA genotype (98K-47-8) and South African genotypes (Glenda, Dr Saunders, Enchore, and Oloyin) which was associated with high GY, PWP, NSPPx, NPP, seed weight per plant (SWP) and harvest index (HI). The identified superior cowpea mutants for grain yield and yield components can be used for cowpea improvement.

Morphological Characterisation and Cyanide Content Determination in Phaseolus lunatus Linn. (Lima Beans) Accessions

Lima bean (Phaseolus lunatus Linn.) is one of the important legumes in developing countries. The study was carried out to evaluate the morphological characters and determine the amount of cyanide in lima beans. A total of 15 Lima bean accessions were obtained from the genebank of Genetic Resource Centre, International Institute of Tropical Agriculture (IITA) Ibadan, Oyo state, Nigeria and laid in Complete Randomised Design with three replicates. Morphological characters were evaluated based on the descriptors proposed by the International Plant Genetic Resources Institute, while hydrogen cyanide (HCN) content was determined using alkaline picrate colorimetric method. Six of the accessions (2005-014, 2006-003A, 2006-003B, 2006- 005A, PS-16 and TPl-2429) having best yield, moderate yield and lowest yield were selected for cyanide determination. Result showed that the accessions varied morphologically. The highest yielding accessions were TPl-2429, 2005- 014, 2006-003A and 2005-011, while 2006-003B and TPl-178 have moderate yields. Accession 2005-014 had the highest growth characters, followed by 2006-015 and 2006-003A which showed good quality. Lower amounts of cyanide were detected in 2005-014 and PS-16 accessions, while 2006-003A, 2006-003B and 2006-005A accessions did not show cyanide contents. Therefore, TPl-2429, 2006-003A and 2005-011 accessions which showed higher growth and yield with no cyanide content could be further improved in breeding of lima beans.

Diversity and Abundance of Amenity Trees in the Premises of International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria

Amenity trees are an essential element of most urban communities, contributing significantly to human well-being and improving environmental quality. Good knowledge of the diversity and abundance of trees in our environment and their importance can help promote conservation, which is essential for sustainability. This study aimed at assessing the diversity and abundance of amenity trees on the premises of the International Institute of Tropical Agriculture (IITA), Ibadan Nigeria. The institute was divided into working and residential areas. The trees in the study area were identified using a walking and windshield survey. A total population of 2626 trees from 126 species and 42 families were identified on the premises of IITA. The highest tree population of 523 trees was recorded in the Tropical Crescent residential area with 321 trees of Lagerstroemia speciosa being the most frequent species. Across working and residential areas, Elaeis guineensis was the most frequent species accounting for 19.92% of the total tree population. A Shannon-Wiener Diversity Index (H’) of 3.383 and species evenness of 0.43 was obtained from the study area. The high values of diversity indices obtained indicate that IITA premises are rich in diverse tree species both indigenous and exotic hence should be referenced as a good urban landscape. The current management practices can be recommended for other institutions.

Genetic structure analysis and identifying key founder inbred lines in diverse elite sub-tropical maize inbred lines

Understanding the genetic relationships between the key founder inbred lines and derived inbred lines could provide insight into the breeding history and the structure of genetic diversity of the available elite inbred lines with desirable target traits. The maize improvement program at the International Institute of Tropical Agriculture (IITA) analyzed the pedigree information of 623 sub-tropical maize inbred lines generated at the IITA maize breeding program to identify the key founder inbred lines. We also used 5032 SNP markers to assess the genetic similarities of the founder inbred lines with their progenies subsequently developed for specific target traits. The results of pedigree analysis and SNP markers-based similarity scores identified 20 key founder inbred lines with significant contributions to the development of drought tolerant, early maturing, productive, Striga resistant, provitamin A enriched, and quality protein maize inbred lines. In our breeding program, line TZMi501 belonging to a flint heterotic group (HGA), and TZMi407-S and TZMi214, representing the dent heterotic group (HGB), were identified as the most useful founder inbred lines. The 623 inbred lines were consistently separated into four clusters based on Ward’s hierarchical clustering, structure, and principal component analyses, with the 20 founder inbred lines spread into all clusters. The founder inbred lines were more genetically related to the productive inbred lines but showed genetic divergence from the provitamin A enriched inbred lines. These results provide a better understanding of the breeding history of the sub-tropical maize inbred lines to facilitate parental selection aligned to existing heterotic groups for use in breeding programs targeting the improvement of essential traits in maize.