Nigeria is the largest producer and consumer of soybean in Sub-Saharan Africa with a low yield of less than 1 ton per hectare. Plant diseases play a major role in yield reduction for the crop. The study was to investigate the incidence and severity of fungal and common viral diseases of some soybean lines and determine their effects on soybean yield. Nineteen newly developed soybean lines with two local checks were evaluated. Fungal isolates were identified using cultural and morphological characteristics while Antigen Coated Plate-Enzyme-Linked Immunosorbent Assay was used for detecting viruses. Data were subjected to Analysis of Variance and means were separated at P = 0.05 using Duncan’s Multiple Range Test. Eight fungi isolated from diseased soybean plants were Fusarium oxysporum, Choanephora infundibulifera, Colletotrichum gloeosporioides, Culvularia spp., Fusarium verticilloides, Aspergillus flavus, Lasiodiplodia theobromae and Pestalotia spp., while the common viral symptom on the field was mosaic and mottling. F. oxysporum recorded the highest frequency of occurrence of 40.91% and 22.30%, in both years. F. oxysporum and C. infundibulifera showed characteristics symptoms of blight when used for pathogenicity on both checks. The soybean lines differed significantly [P = 0.05] in disease incidence and severity for both fungi and viral diseases. All lines were positive for Cowpea mild mottle virus [CPMMV] in 2016. All the lines evaluated were moderately resistant to leaf blight disease. The study concluded that these lines were tolerant to all observable diseases occasioned by their abilities to produce higher grain yield compared with the local checks, despite the high disease incidence and severity.

Low soil nitrogen (low-N) and stem borer attack are two of the major stresses limiting maize production in West and Central Africa (WCA). Thus, there is need to intensify efforts aimed at identifying inbred lines with resistance and tolerance to these stresses for hybrid development. The objectives of the study were to determine the combining ability of maize inbred lines, classify them into heterotic groups using both conventional and marker-based approaches, compare the efficiency of the different grouping methods and evaluate the performance of the hybrids generated from the inbred lines under contrasting environments. Ten white maize inbred lines with varying levels of resistance to stem borers were selected and crossed in a diallel in 2015. The resulting 45 hybrids were evaluated together with five checks in 10 environments under low-N, artificial stem borer infestation and non-stress conditions in Nigeria. General combining ability (GCA) and specific combining ability (SCA) were highly significant (p ≤ 0.01) for most of the traits studied but GCA was predominant over SCA under each and across research conditions. Inbred line 2 combined significant positive GCA for grain yield with significant negative GCA for traits of resistance to stem borers and tolerance to low-N. Each of the grouping methods classified the inbred lines into 3 heterotic groups but SCA and heterotic groups’ specific and general combining ability had the joint highest breeding efficiency. Hybrids 1 × 4, 2 × 3, 1 × 6 and 2 × 5 were identified to be high yielding and stable across environments and can serve as candidates for further on-farm evaluations and eventual release in WCA.

Background: The success of hybridization programme depends on the combining ability of parental lines. Methods: Seven soybean genotypes and all their partial diallel crosses in the F2 generation were evaluated in a randomized complete block design at two locations in Nigeria, during the 2017-2018 growing season. Result: Analysis of variance showed that both environments and genotypes were significantly different for all measured traits. The genotype TGx 1988-5F was the best general combiner for earliness in flowering and poding, while TGx 1448-2E was the best general combiner for number of pods/plant and seed yield/plant. Crosses having significant and positive specific combining ability effect for number of pods/plant and seed yield/plant were TGx 1485-1D × TGx 1448-2E and TGx 1988-5F × TGx 1989-19F, respectively. Genotypes TGx 1988-5F and TGx 1448-2E exhibiting good general combining ability for earliness and seed yield/plant, are thus, promising for utilization in the future hybridization programme for soybean improvement.

Rice is staple food in many countries of Africa and a major part of the diet in many others. However, Africa’s demand for rice exceeds production with the deficit of 40% being imported. One way to improve Africa’s rice production is through breeding high yielding varieties suitable for the different environment conditions. This study was conducted to assess the genetic variability and stability performance of 48 lowland rice genotypes including 37 interspecific ( Oryza glaberrima × Oryza sativa ssp. indica ) and 11 intraspecific ( O. sativa ssp. indica × O. sativa ssp . indica ) in 12 environments in Nigeria, Benin Republic and Togo using Additive Main Effect and Multiplicative Interaction (AMMI) and Genotype+ Genotype x Environment (GGE) biplot models. The combined analysis of variance revealed significant differences (P<0.01) among the genotypes, environments, and genotypes x environment interaction. Both the AMMI and GGE models identified NERICA-L8 and NERICA-LI2 as the best genotypes for cultivation across environments. Ouedeme environments in Benin Republic were the most stable and ideal for rice cultivation, while Ibadan sites were the most unstable. TOG 5681 had the least yield and was the most unstable across seasons. Genetic diversity was analyzed using 22 important morpho-agronomic traits and 50 simple sequence repeat (SSR) markers and the results were subjected to principal components analysis (PCA). The results revealed that the first eight PC axes (PC1–8) accounted for 75.13% of the total variation, while PC1–4 accounted for 50.39% of the total variation among rice genotypes. However, 10 of the 50 SSR markers were polymorphic and generated 49 alleles (average = 4.9 alleles per locus), suggesting moderate to substantial genetic diversity among the rice genotypes. The polymorphic information content (PIC) ranged from 0.24 to 0.65, with an average PIC value of 0.45. Two structured populations were observed which clustered into five heterotic groups and an outgroup, respectively. This suggests that heterosis could be exploited in the next hybridization program by crossing one of the genotypes in any SSR marker-defined cluster, with the rice accession TOG 5681 in cluster I. The results of this study suggest that morpho-agronomic traits should be used to compliment SSR data in rice diversity studies, especially if a few polymorphic SSR markers are to be used.

Crosses were made in line × tester mating design between a set of five IITA soybean released varieties and three plant introduced (PI) accessions obtained from World Vegetable Center, Taiwan. In order to produce sufficient seeds, F1 crosses were selfed, subsequently F2 populations along with their parents were planted in a randomized complete block design at two locations in Nigeria with three replications. Agronomic traits viz. days to flowering, days to poding, plant height, number of pods/plant and seed yield/plant were measured. Testers and lines showed significant differences for all the measured traits except days to flowering for testers. Considering the significance and magnitude of general combining ability (GCA) effect, line TGx 1988-5F was observed desirable for earliness, while line TGx 1989-19F was the best combiner for number of pods/plant and seed yield/plant. On the other hand, best tester for seed yield was PI 230970. Crosses TGx 1835-10E × PI 459025B and TGx 1987-62F × PI 459025B had significant and highest SCA effect for seed yield/plant. These two crosses appeared to be most promising for soybean yield improvement programme.

Eggplant is a popular vegetable/fruit consumed in Nigeria either in the fresh form or cooked. To study the genetic diversity; estimate the heritability and genetic advances of the fruit yield and to determine quantitative traits of this crop, a total of seventy-eight accessions of eggplants were evaluated in 2011/2012 at the vegetable research field of the National Horticultural Research Institute, Ibadan. Data on quantitative traits were subjected to Principal Component Analysis (PCA), Single Linkage Cluster Analysis (SLCA), Fastclus technique and Analysis of Variance. Phenotypic and genotypic coefficients of variability (PCV and GCC), heritability and genetic advance of the yield components were estimated. The first four principal component axes accounted for 79.47% of total variability. PCA1 with largest variation (40.49%) was loaded with petiole length, fruit diameter, number of fruits and fruit yield/plant. The SLCA summarized relationship among the 78 accessions into three groups at 50% level of similarity while Fastclus technique separated them into sixteen clusters. Significant variation occurred among the eggplant accessions with respect to most of the traits studied. High estimates of broad-sense heritability (˃ 85%) suggested that the traits were highly heritable and under additive gene effect. Magnitude of PCV higher than GCV for some traits indicated that environment had great influence on these traits. Keywords: Genetic diversity, quantitative traits, variation, heritability, genetic advance

Background: Lowering the nitrogen demand is the most cost effective and sustainable option to increase grain yield of maize in poor fertility soil. Aim: This study was conducted to estimate the variability and inter-traits’ association of white and yellow hybrid maize in soil nitrogen-nutritional stress and optimal conditions. Materials and Methods: 150 white and 66 yellow single cross hybrid maize were evaluated in contrasting soil (stress and optimal) N conditions in Ibadan in 2014 and 2015. The trial for the white maize was laid out in 19 × 8 lattice design while the yellow maize was experimented in randomized complete block design. Each trial was replicated three times. Data were collected on days to anthesis (DTA), days to silking (DTS), plant height (PH), ear height (EH), anthesis-silking-interval (ASI) and grain yield (GY) were estimated while leaf senescence (LS), plant aspect (PASP) and ear aspect (EASP) were scored. Data collected were subjected to analysis of variance while variances and broad sense heritability were calculated and rated. Results: Greater variability existed among white maize than the yellow maize for the traits. Inheritance of the traits can be predicted in optimal N than stress condition. Additive genes action was responsible for inheritance of DTA and DTS while both additive and non-additive control the GY, PH, EH and LS of the white maize in both N conditions. For yellow maize, the DTA and DTS were controlled by additive genes action in both N conditions. The GY, ASI, PH, EH and LS were governed by both additive and non-additive genes actions in N stress condition. Additive genes action is responsible for inheritance of PH and EH while both additive and non-additive actions govern inheritance of GY, ASI and LS in optimal condition. The GY had positive relationship with the DTA, DTS and LS in both N conditions for the white maize while the GY positively correlated with PH, EH and LS in N stress, but with ASI only in optimal condition for the yellow maize. Conclusion: Grain yield, flowering, height and leaf senescence can be used in selecting maize for nitrogen-use-efficiency.

Increasing demand, soil cultivation pressure and adverse climate change effects necessitated maize production in nitrogen stress soils. This study examined the general combining ability (GCA) of 12 maize inbreds and specific combining ability of their crosses for agronomic traits under varied nitrogen conditions. GCA accounted for 53% of the variation for grain yield (GY) under stress and 40% under optimal condition. GCA contributed over 59% for days to anthesis (DTA) and days to silking (DTS), anthesis-silking-interval (ASI) and ear aspect (EASP) under both conditions. BD74-165 and BD74-161 had positive significant GCA for GY under stress with TZEI12 under optimal and BD74-222 under both conditions. TZEI13 and TZEI16 had positive significant GCA for DTA and ASI under stress, and TZEI12, TZEI11 and BD74-161 under optimal. Additive genes control DTA, DTS and PH; non-additive genes were responsible for ASI, PASP and EASP while both additive and non-additive genes governed inheritance of GY, EH and leaf-senescence (SEN) under stress. Inheritance of GY, ASI, PH, PASP and EASP were due to non-additive genes; DTA and DTS to additive genes while additive and non-additive genes control EH and SEN under opti­mal condition. Inbreds with significant GCA can be parents for GY improvement under respective conditions. Keywords: Combining ability; diallel; low nitrogen; maize lines; stress tolerance

Presence of genotypic differences in maize ( Zea mays L.) grain yield in multi-environments would help plant breeders to make logical decisions in improvement programmes of the crop. Hence, the grain yield performance, heterosis and stability in hybrid maize in varied soil nitrogen (N) conditions in Nigeria were assessed using multiple biometrical techniques. Grain yield performance, heterosis and stability of 150 single cross hybrid maize were assessed with checks in severe N stress, N stress and optimal conditions in a replicated trial laid out in 19 × 8 lattice design for 2 years. The grain yield was subjected to analysis of variance for each N condition and combined across years. Heterosis was estimated for the trait, additive mean effects and multiplicative interaction (AMMI); and genotype + genotype × environment (GGE) models were used to analyse the hybrids’ yield stability. The AMMI captured 93.7%; while GGE bi-plot accounted for 88.7% of total variation among the hybrids. Eight hybrids had high yields across the N conditions. Genotypes and environments affected heterosis for grain yield. Hybrids TZEI7×BD74-399, BD74-179×BD74-55 and BD74-175×BD74-147 were the most ideal genotypes for the N conditions; while severe N stress condition was ideal test environment. Hybrid BD74-170×BD74-31 adapted most to N stress; while TZEI1×BD74-399 adapted most to severe N stress and to optimal conditions. Based on yield, heterosis and stability, hybrids involving inbred line BD74-171 were recommended for N stress; while those with inbred lines TZEI1, TZEI4 BD74-170, BD74-128, BD74-179 and BD74-175 were adapted to N stress and optimal conditions. Key words: AMMI, GGE biplot, Zea mays

African eggplant is an important fruit and leafy vegetable in Africa. Heterosis over mid and better parents was estimated in eight crosses of eggplant involving eight pure lines in a field experiment in 2012 and 2013 cropping seasons. The experiment was laid out using a randomized complete block design with three replications. Collected data was subjected to analysis of variance and significant differences were further subjected to Duncan Multiple Range Test. The aim of this study was to identify superior hybrids that can be advanced in the eggplant breeding program for improved yield and related traits. Significant variation was observed among all traits measured for the parents and hybrids. The highest fruit number was observed in NHS10-40 and in NHS 10-71 x NHS 10-40 among the parents and hybrids respectively. The highest heterosis was recorded in the cross between NHS10-71 x NHS10-40.

Freely nodulating soybean genotypes vary in their phosphorus (P) uptake and P-use efficiency (PUE) in low-P soils. Understanding the genetic basis of these genotypes' performance is essential for effective breeding. To study the inheritance of PUE, we conducted crosses using two high-PUE genotypes, two moderate-PUE genotypes and two inefficient-PUE genotypes, and obtained F-1, F2,BC1 and BC2 populations. The inheritance of PUE was evaluated using a randomized complete block design. A generation mean analysis of phenotypic data showed that PUE was heritable, with complex inheritance patterns and the presence of additive, dominance and epistatic gene effects. Seed P, shoot P, root P, P-incorporation efficiency and PUE were largely quantitatively inherited traits. There were dominance, additive x additive and dominance x dominance gene effects on PUE, grain yield, shoot dry weight, 100-seed weight, root dry weight and shoot dry matter per unit P for populations grown under low-P conditions. Dominance effects were generally greater than additive effects on PUE-related indices. These PUE indices can be used to select P-efficient soybean genotypes from segregating populations.

Grain yield is a complex quantitative trait that depends on a number of other traits for selection. This study was carried out to reveal the pattern of association with and contribution of traits to grain yield in two maize populations evaluated in three agro-ecological zones of South-Western Nigeria during the 2014 cropping season. The experiment consisted of 10 top-cross and 10 three-way cross maize hybrids, laid out in a randomised complete block design with three replications. Genotypic and phenotypic correlation coefficients and path co-efficient analyses were performed for each hybrid population across the three locations. Results showed significant (p≤0.05) differences between the two hybrid populations for all the traits mentioned except days to 50% anthesis, ear diameter and 100-grain weight. Field weight in both hybrid populations, number of kernel rows per cob, ear diameter and ear height in top-cross hybrids, as well as ear length and 100-grain weight in the three-way cross hybrids were directly correlated with grain yield. The link between direct and indirect effects on grain yield depends on hybrid population, although some traits showed similar direct effects in both hybrid populations. These traits can be used as the main criteria for grain yield improvement in the respective hybrid populations. Key words: Correlation, path coefficient analysis, hybrid populations, maize (Zea mays L.), grain yield.

Apomixis is seed and embryo formation without fertilization. A study was carried out from August, 2012 to May, 2014 in order to investigate the possibility of occurrence of apomixis in fluted pumpkin (Telfairia occidentalis Hook. F.) using emasculation method. Five genotypes of fluted pumpkin were used. Ten plants from each genotype were planted out in a screened environment at the Original Research Article Fayeun et al.; AJEA, 10(1): 1-10, 2016; Article no.AJEA.15261 2 department of Crop, Soil and Pest Management, Federal University of Technology, Akure. The crop being dioecious, all the male plants were emasculated (by total removal from the site) as soon as they were noticed, leaving only the female plants. Seeds obtained from the fruits of isolated female plants were later subjected to viability test. After several weeks of flowering, flowers and developing ovaries abortion, they eventually set fruits. All the genotypes produced fruits (one or two) though at different times. Both apomictic and parthenocarpic fruits were produced. The seeds obtained from the apomictic fruits of all the genotypes had high seedling emergence percentage and good seedling vigour. Apomictic fruits, seeds and seedlings were similar to those of sexually produced fruits. The observed facultative apomixis could be as a result of natural selection. This study confirms that apomictic form of reproduction occurs naturally in fluted pumpkin. Facultative apomixis in the fluted pumpkin is being reported for the first time and its implication in the genetic improvement of the crop is discussed.

Understanding the genetic variability, heritability and genetic advance of traits in any plant population is an im- portant pre-requisite for selection program. This study was designed to assess the magnitude of genetic variabili- ty, heritability and genetic advance of traits in top-cross and three-way cross maize (Zea mays L) hybrids evaluated at three locations in South-Western Nigeria. The trial consisted of ten genotypes each of top-cross and three-way cross hybrids arranged in randomized complete block design with three replications. Data on grain yield and other desirable traits across the three locations were used to estimate the genetic variability parameters, heritability and genetic advance (GA). Highly significant (P ≤ 0.01) differences were detected within each hybrid class for all the traits. Traits evaluated in this study exhibited different levels of variability, heritability and genetic advance between the two hybrid classes. Low to moderate phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were recorded. Also, low to very high heritability and low to high GA values were recorded for all the traits measured in the top-cross hybrids, whereas the three-way cross hybrids exhibited low to moderately high heritability estimates and low to moderate GA values. Grain yield and field weight showed moderate GCV, moderately high heritability and high GA values in top-cross hybrids. These characters exhibited moderate GCV but low heritability and GA values in three-way hybrids. More characters in top-cross hybrids revealed sufficient amount of variability than in three-way cross hybrids, thus offer scope for genetic improvement through selection.

Knowledge of floral biology is essential to crop improvement. Ten genotypes of fluted pumpkin (Telfairia occidentalis) were observed for floral morphology, phenology and insect visitation for two consecutive years. Functional dioecy of fluted pumpkin was confirmed, whereas none of the studied genotypes was monoecious. Floral structures differed significantly among the genotypes. Both male and female flowers were symmetrical, pentasepalous, fimbriate and non-bright pentapetalous, but male flowers were more numerous. Male inflorescences emerged from 11 to 14 weeks after planting and the female flower buds appeared about 4 weeks later. The flowering period of the male flowers was longer than that of female flowers and both gender flowering periods coincided for a specific interval. It took between 11 to 14 days from bud initiation to anthesis and flowering ceased when there were occurrences of successful fruits set. In both gender flowers petals started unfurling at around 6.00 pm and full bloom was achieved by dawn, while petal shrivelled at sun set (between 6.30 pm to 7.30 pm). The anthers dehisced at anthesis of the male flowers; the pollen grains were whitish and sticky. Only the male flowers have nectar and pollen and this may explain infrequent female flowers visitation. Hover flies (Cheilosia species) were the major floral visitors observed.

Genotypic, phenotypic and environmental correlation coefficients were calculated for fourteen characters in twenty-three cassava accessions planted in Ibadan (7°30`N, 3°54`E) and Mokwa (9°30`N, 5°54`E), Nigeria in 2004. The aim of this study was to determine the contribution of plant characters to storage tuber yield. The field experiment was conducted in a randomized complete block design with three replicates. Genotypic correlation coefficients of six characters that exhibited significant association with tuber yield were partitioned into direct and indirect effects. Stem diameter, leaf chlorophyll concentration, tuber diameter, fresh weight of tubers per plant, number of tubers per plant and dry matter of fresh tuber were found to be positively and significantly correlated with dry tuber yield per plant. Leaf chlorophyll concentration, fresh weight of tubers per plant and dry matter of fresh tuber had positive direct effects on dry tuber yield per plant. It was concluded that knowledge of the relationship of characters that had significant association with tuber yield will aid the selection of genotypes that have high tuber yield. The results suggest that fresh weight of tubers per plant is the most reliable index of dry tuber yield per plant in the regions studied.

Genetic variability of agronomic traits of crops broadens the gene pool of crops. Repeatability and genetic ad- vance determine the effectiveness of selection in breeding programme. Hence, phenotypic and genotypic vari- ances, genotypic coefficient of variation, repeatability and expected genetic advance were estimated for three flowering and six morphological traits of white kernel low nitrogen donor maize inbred lines. Significant difference existed in the nine traits. Genotypic and phenotypic variances were equal for floral traits. Thus, gene actions for the traits was additive. Repeatability was high for the nine traits. In addition to high repeatability, anthesis-silking interval showed high genetic advance with high coefficient of variation suggesting its efficiency for selection. Phenotypic and genotypic correlations of grain yield with each of days to anthesis, plant height, ear height, leaf area and number of ear per plant were positive and significant. Genetic effect for grain yield correlated with that of days to silking, but this was not for phenotypic effect. Any of these traits can be selected for grain yield and the lines studied were considered suitable as gene pool in maize breeding for nitrogen stress tolerance. Path analysis showed that days to silking, leaf area and ear per plant had high positive effect with grain yield of the crop.

Accurate knowledge of intra-specific diversity of underutilized crop species is a prerequisite for their genetic improvement and utilization. The diversity of 77 accessions of African yam bean (AYB, Sphenostylis stenocarpa) was assessed by amplified fragment length polymorphism (AFLP) markers. A total of EcoRI/MseI primer pairs were selected and 227 AFLP bands were generated, of which 59(26%) were found to be polymorphic in the 77 accessions of AYB. The most efficient primer combination for polymorphic detection was E-ACT/M-CAG with a polymorphic efficiency of 85.5%, while the least efficient was E-AGC/M-CAG with a polymorphic efficiency of 80.6%. The Jaccard genetic distance among the accessions of AYB ranged between 0.048 and 0.842 with a mean of 0.444. TSs98 and TSs104B were found to be the most similar accessions with a genetic similarity of 0.952. The neighbour-joining dendrogram grouped the 77 accessions of AYB into four distinct clusters comprising 8, 20, 21 and 28 accessions. The major clustering of the accessions was not related to their geographical origin. Cluster I was found to be the most diverse. The mean fixation index (0.203) and the mean expected heterozygosity (0.284) revealed a broad genetic base of the AYB accessions. The same germplasm set was previously evaluated for several agro-morphological traits. As the collection of additional AYB germplasm continues, the phenotypic profile, the clustering of the accessions and the AFLP primer combinations from this study can be used to augment breeding programmes.

A study was conducted during 2008 to 2009 in 12 environments in Nigeria, Benin Republic and Togo to evaluate genetic variation and heritability of yield and related traits in 48 rice genotypes. The experiments were laid out in a randomized complete block design (RCBD) with three replications. Genotypes differed significantly at p > 0.001 for all the traits studied, which implies that the genotypes contain adequate genetic variability. Phenotypic coefficients of variation (PCV) were higher than genotypic coefficients of variation (GCV) in all the characters across the 12 environments. High heritability estimates were obtained for days to flowering (91.37), days to maturity (86.86), plant height at maturity, number of tiller per meter square, panicle shattering, panicle threshability, panicle per meter and panicle length (72.21) suggesting that the traits are primarily under genetic control. High estimates of heritability, GCV and genetic advance (GA) observed for grain yield is an indication that selection for grain yield could be achieved through phenotypic performance. Furthermore, high estimates of heritability, GA and GCV recorded in these characters could be explained by additive gene action. Low estimates of heritability, GCV and GA recorded for grain yield and number of grains per panicle could be due to non-additive gene effect suggesting that these traits were less responsive to specific environment influences. Grain yield recorded highly significant positive correlation with panicle length (0.28), leaf width (0.40), grain length (0.30), number of panicles per meter square (0.19) and1000-grain weight (0.17). It correlated negatively with basal leaf sheath coloration (-0.33) and grain width (-0.20) in the 12 environments. The current study indicated that more number of tillers, panicles per meter square, long panicles, high number of primary and secondary branch panicles and large 1000-grain weight are important yield related traits and could be used for selection in rice breeding programs. Key words: Correlation coefficients, heritability, phenotypic coefficients, rice, variability, yield components.