scholarly works in Agronomy
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Item Field performance of shrunken-2 super-sweet corn populations derived from tropical field maize × shrunken-2 super-sweet corn crosses in Ibadan, Nigeria(Academic Journal, 2019-05) Abe, A.; Lasisi, O. A.; Akinrinbola, O. J.The conversion of tropical field corn genotypes into sweet corn could broaden the genetic base and improve yield and adaptation of sweet corn varieties. In this study, the performance of shrunken-2 (sh2) super-sweet corn populations derived from crosses between a sh2 population and tropical field corn genotypes were evaluated in Ibadan. experiments were conducted using randomised complete block design with three replicates. Data were collected on agronomic and fresh ear yield traits, and then subjected to analysis of variance. Significant genotypic differences were observed among the populations with most of the derived populations significantly superior to the donor population for most of the traits. Yield of marketable cobs ranged from 5.80 to 7.63 t/ha (mean = 6.84 t/ha). Six derived populations had significantly higher yield of marketable cobs than the donor population. On the average, 83.1% of the number of cobs harvested was marketable. Husk cover scores ranged from 2.8 to 6.8, with all the derived populations having significantly lower husk cover scores than the donor population. The results indicated that the conversion of the field corn genotypes into super-sweet corn was effective in the development of new super-sweet corn populations. The observed genetic differences could be exploited in further breeding programmes.Item Genetic variability, heritability and genetic advance in shrunken-2 super-sweet corn (zea mays L. saccharata) populations(Academic Journal, 2019-04) Abe, A.; Adelegan, C. A.Inbred line development requires information on the nature and magnitude of genetic variability and transmissibility of desired trait in source populations. In this study, the level of genetic variability, heritability and genetic advance of thirteen agronomic and fresh yield traits among twelve shrunken-2 super-sweet corn populations were evaluated. Field experiments were conducted for two years in Ibadan, Nigeria using a randomised complete block design with three replicates. Estimates of genetic variability components, broad-sense heritability and genetic advance were computed for each trait. All the traits exhibited significant genotypic differences. Genotypic variance was significant for number of marketable cobs, yield of cobs, number of cobs, number of kernel rows, husk cover, ear height and days to anthesis, while environmental variance was significant for all the traits. Phenotypic coefficients of variation were higher than the corresponding genotypic coefficients of variation for all traits. Broad sense heritability ranged from 22.2% for anthesis-silking interval to 85.1% for husk cover. The genetic advance was high (32.7%) for husk cover, medium (12.0%) for yield of cobs and low for other traits. Genetic variability was present among the shrunken-2 super-sweet corn populations. Opportunities abound for further improvement of the populations and extraction of lines for hybrid seed production.Item Agronomic performance of tropical × tropical and tropical × temperate single-cross maize hybrids in Ibadan, Nigeria(Obafemi Awolowo University, Ile-Ife, Nigeria, 2018) Abe, A.The productivity of tropical maize could be improved by the introgression of beneficial alleles from temperate germplasm. Ten tropical × temperate and two temperate × temperate single cross hybrids were developed and evaluated for their performance alongside four tropical × tropical hybrids. The tropical × temperate hybrids were developed by crossing the temperate inbred lines B73 and Mo17 as males to the tropical inbred lines 4001, 4008, 9613, 9432 and KU1409. The experimental design was randomized complete block with three replicates. Data were collected on seedling emergence, flowering traits, grain yield and yield components and subjected to analysis of variance. Significant genotypic differences were observed among the hybrids for all measured traits. The tropical × tropical crosses had significantly higher grain yield, ear width, kernel weight and kernel depth than the crosses involving the tropical × temperate inbred lines. However, the tropical × tropical hybrids had lower emergence percentage, but higher emergence index and emergence rate index than the tropical × temperate hybrids. Grain yield ranged from 3.38 (Mo17 × B73) to 6.02 t/ha (4001 × 4008) and was in the order temperate × temperate < tropical × temperate < tropical × tropical hybrids. On average, tropical × B73 hybrids had higher grain yields than tropical × Mo17 hybrids. Four of the tropical × temperate hybrids (4001 × B73, 4008 × B73, KU1409 × B73 and 9432 × Mo17) had grain yields equal to or above the overall average. These hybrids have considerable potential and could be exploited to improve and broaden the grain yield of tropical maize.Item Green ear yield potential of tropical field maize at two levels of nitrogen fertiliser application in Ibadan, Nigeria(Experimental Institute for Cereal Research, 2015) Abe, A.; Akinrinola, T. B.Green maize plays a significant role in the social and economic life of the peoples of the humid forest and derived savannah agro-ecologies of West and Central Africa. Appropriate strategies for its production would contribute significantly to sustainable agriculture. Fourteen tropical field maize genotypes, consisting of hybrids and open pollinated varieties (OPVs), were evaluated in field trials for green ear yield at two levels (30 and 60 kg ha-1) of nitrogen fertilizer application during the main cropping seasons of 2012 and 2013. A factorial in a split plot design with three replications was used. Fertilizer levels were main plots and maize genotypes subplots. Highly significant genotype, N level and genotype × N level effects were observed for all traits considered. The range in yield of marketable cobs at 30 kg N ha-1 and 60 kg N ha-1 were 98.4% and 108.6% of the respective means. The number and yield of ears, yield of cobs and number and yield of marketable cobs were significantly reduced at 30 kg N ha-1. The percentage reduction in yield of marketable cobs was 55.9%. Yield of marketable cobs and other measured green ear yield variables at 30 kg N ha-1 for OPVs were significantly higher than for the hybrids, while the differences were not significant at 60 kg N ha-1. Suwan-1 STR produced the highest number and yield of marketable cobs per hectare both at 60 kg N ha-1 and across N levels. At 30 kg N ha-1, the top yielding genotypes were ACR97 TZL COMP1 C2 (2.82 t ha-1), TZE COMP3 C2 (2.71 t ha-1) and 9044-27 STR (2.51 t ha-1), while the best three genotypes at 60 kg N ha-1 were Suwan-1 (6.56 t ha-1), AK96DMR-L-SR-W (5.91 t ha-1) and 9144-4 (5.28 t ha-1). Yield of marketable cobs in this study at 30 and 60 kg N ha-1 was 46.5 and 49.1% of the yield of ears ha-1, respectively. Genetic variation for green ear yield was present among the maize genotypes studied and this was greatly influenced by the level of N fertiliser application.Item Performance of tropical maize hybrids under conditions of low and optimum levels of nitrogen fertilizer application – grain yield, biomass production and nitrogen accumulation(Società Botanica Italiana, 2013) Abe, A.; Adetimirin, V. O.; Menkir, A.; Moose, S. P.; Olaniyan, A. B; Olaniyan, A. BNitrogen (N) is the most limiting mineral nutrient in the soils of the major maize producing areas of West and Cen¬tral Africa. Low soil N and sub-optimal application of N fertilizers lead to N deficiency and poor grain yield (GY) in maize. Maize varieties with improved grain yield under low soil N and increased performance under optimal N availability could be beneficial to low input agriculture. This study evaluated the performance of a selection of ex¬perimental and commercial hybrids under suboptimal and optimal N fertilizer applications. Significant differences were observed among the hybrids, as well as significant interactions between hybrid and N level for GY and other measured attributes, with the severity of variation increasing as the level of N decreases. Mean GY reductions across the years was 76.5% at no-N and 35.4% at low-N. Depending on N treatment, GY varied from 0.48 to 4.42 Mg ha-1, grain N content from 0.17 to 1.26 g plant-1, total N content at harvest from 0.33 to 2.00 g plant-1, above ground biomass at silking from 30.6 to 91.2 g plant-1 and at maturity from 39.9 to 191.1 g plant-1. Number of ker¬nels was the GY component most severely reduced by N stress and had significant (p ≤ 0.001) positive correlation with GY at all N levels. Six hybrids (4001/4008, KU1409/4008, KU1409/9613, 4008/1808, 4058/Fun 47-4, and 1824/9432) which showed consistent above average grain yields under no-N, low-N, high-N and across N levels were found and their use could further be investigated.Item Genetic variation for nitrogen-Use efficiency among selected tropical maize hybrids differing in grain yield potential(Taylor & Francis, 2012) Abe, A.; Menkir, A.; Moose, S. P.; Victor, O. A.; Olaniyan, A. BLow soil nitrogen (N) and sub-optimal N fertilizer applications result in poor grain yield (GY) in maize. Genotypes with improved N-use efficiency (NUE) are particularly beneficial to low-input agriculture. Information on the relative importance of the main components of NUE will facilitate genetic improvement of tropical maize for NUE. This study evaluated genetic variation for NUE among tropical maize hybrids selected for contrasting responses to N. The hybrids were grown in replicated trials from 2006 to 2008 where plots received either no (0 kg N/ha), low (30 kg N/ha), or high (90 kg N/ha) levels of supplemental N. The results documented significant genetic variation for GY and measured NUE component traits among the hybrids, as well as significant interactions between hybrid and N level for all traits except nitrogen harvest index. Under low N, NUE, NUPE, and NUTE increased by 61%, 21%, and 42%, respectively. Grain yield was significantly and positively correlated with NUE, NUPE, and NUTE at both low N and high N. Both NUPE and NUTE were significantly and positively correlated to NUE. Five hybrids (4001/4008, KU1409/4008, KU1409/9613, 4008/1808, and 1824/9432) produced similar GY at both low N and high N but differed in their NUPE and NUTE. Genetic variation was present among the maize hybrids studied for NUE and its components. Although both NUPE and NUTE contributed to high grain yield, the relative importance of the two traits to NUE varied with genotype and level of N.Item Performance of tropical maize hybrids under conditions of low and optimum levels of nitrogen fertilizer application – grain yield, biomass production and nitrogen accumulation(2013) Abe, A.; Adetimirin, V. O.; Menkir, A.; Moose, S. P.; Olaniyan, A. B.Nitrogen (N) is the most limiting mineral nutrient in the soils of the major maize producing areas of West and Cen¬tral Africa. Low soil N and sub-optimal application of N fertilizers lead to N deficiency and poor grain yield (GY) in maize. Maize varieties with improved grain yield under low soil N and increased performance under optimal N availability could be beneficial to low input agriculture. This study evaluated the performance of a selection of ex¬perimental and commercial hybrids under suboptimal and optimal N fertilizer applications. Significant differences were observed among the hybrids, as well as significant interactions between hybrid and N level for GY and other measured attributes, with the severity of variation increasing as the level of N decreases. Mean GY reductions across the years was 76.5% at no-N and 35.4% at low-N. Depending on N treatment, GY varied from 0.48 to 4.42 Mg ha-1, grain N content from 0.17 to 1.26 g plant-1, total N content at harvest from 0.33 to 2.00 g plant-1, above ground biomass at silking from 30.6 to 91.2 g plant-1 and at maturity from 39.9 to 191.1 g plant-1. Number of kernels was the GY component most severely reduced by N stress and had significant (p ≤ 0.001) positive correlation with GY at all N levels. Six hybrids (4001/4008, KU1409/4008, KU1409/9613, 4008/1808, 4058/Fun 47-4, and 1824/9432) which showed consistent above average grain yields under no-N, low-N, high-N and across N levels were found and their use could further be investigated.Item Nitrogen-Use Efficiency and Gene Expression Profiling of Tropical Maize Hybrids Selected for Contrasting Responses to Nitrogen Fertilizer(2012) Abe, A.Low soil Nitrogen (N) and sub-optimal N fertilizer application result in low Grain Yield (GY) in maize. Genotypes with improved N-Use Efficiency (NUE) are beneficial to low-input agriculture. To facilitate the genetic improvement of tropical maize for NUE, information is required on the relative importance of N-Uptake Efficiency (NUpE) and N-Utilization Efficiency (NUtE), both components of NUE, the relationships among the gene networks in the developing cob tissue and agronomic traits under limited N. This study was undertaken to evaluate genetic variation for NUE and investigate gene responses in the developing maize cob under sub-optimal N fertilizer application. Fourteen tropical maize hybrids differing in GY under low-N conditions were grown at no-N (0 kg N/ha), low-N (30 kg N/ha), and high-N (90 kg N/ha) in a randomized complete block design with four replications from 2006 to 2008. Data collected on GY and its components, NUE, NUpE, NUtE, and N-related traits were analysed using ANOVA at p=0.05. Path analysis was carried out to capture the intricate relationships among traits related to GY and NUE. Microarray technique using Maize Oligonucleotide array slides containing ~57000 probes were used to identify differentially expressed genes in developing cob tissues harvested from three N-use efficient hybrids compared to an N-use inefficient reference hybrid. Differentially expressed genes were validated by quantitative Real Time Polymerase Chain Reaction (qRT-PCR). Genotype and Genotype × Nitrogen interaction were significant for GY and NUE-related traits. Mean GY across years was reduced by 76.5% at no-N and 35.4% at low-N. It varied from 2.0 to 3.2 Mg/ha at low-N and 3.3 to 4.4 Mg/ha at high-N. Number of kernels (KN) was the GY component most severely reduced under nitrogen stress. Nitrogen use efficiency, NUtE and NUpE increased by 61.4, 42.1 and 21.0% respectively from high-N to low-N. Grain yield was positively and significantly correlated with NUE, NUtE and NUpE at both low-N and high-N. Stover nitrogen content at silking and NUE had strong positive direct effects on GY under low-N and high-N. Both NUtE and NUpE had significant positive direct effects on NUE. The relative importance of NUpE and NUtE varied depending on genotype and environment. Four hybrids (4001/4008, KU1409/9613, KU1409/4008 and 4008/1808) produced similar above average GY at low-N and high-N but differed in their NUpE and NUtE. Gene expression profiling of developing cob tissues revealed that at low-N, 163 of the probes on the array showed differential expression across the test hybrids. Under low-N, the probe MZ00019244 corresponding to the L-asparaginase gene showed the strongest relative mRNA expression in the highest yielding hybrid (KU1409/9613). L-asparaginase mRNA expression level was positively and significantly correlated with GY, KN and NUtE. Genetic variation for nitrogen use efficiency and its components was present among the tropical hybrids. L-asparaginase mRNA expression would be a valuable tool for selecting maize genotypes with high nitrogen utilization efficiency and superior grain yield under low soil nitrogen