Phenological Traits Research Articles

Evaluating Physiological and Yield Indices of Egyptian Barley Cultivars Under Drought Stress Conditions

Climate change significantly threatens crops, mainly through drought stress, affecting barley, which is essential for food and feed globally. Ten barley cultivars were evaluated under normal and drought stress conditions during the 2019/20 and 2020/21 seasons, focusing on traits such as days to heading and maturity, plant height, number of spikes m−2, spike length, 1000-kernel weight, and biological and grain yield. Drought stress significantly reduced most of these traits. The genotypes showed significant differences in their responses to irrigation treatments, with the interaction between seasons and cultivars also being significant for most traits. The grain yield and 1000-kernel weight were among the least affected traits under drought stress, respectively. Notably, Giza138 and Giza126 showed strong drought tolerance, suitable for drought-resilient breeding. In season one, Giza126, Giza134, and Giza138 yielded 13%, 9%, and 11%, respectively, while Giza135 and Giza129 showed higher reductions at 31% and 39%. In season two, Giza126, Giza134, and Giza138 had reductions of 14%, 10%, and 13%, respectively, while Giza135 and Giza129 again exhibited higher reductions at 31% and 38%. These cultivars also showed strong performance across various stress tolerance indices, including the MP, YSI, STI, GMP, and YI. Giza 134 demonstrated the lowest values for the SDI and TOL, indicating superior drought stress tolerance. On the other hand, Giza 129 and Giza 135 were the most sensitive to drought stress, experiencing significant reductions across critical traits, including 6.1% in days to heading, 18.37% in plant height, 28.21% in number of kernel spikes−1, 38.45% in grain yield, and 34.91% in biological yield. In contrast, Giza 138 and Giza 2000 showed better resilience, with lower reductions in the 1000-kernel weight (6.41%) and grain yield (10.61%), making them more suitable for drought-prone conditions. Giza 126 and Giza 132 also exhibited lower sensitivity, with minimal reductions in days to heading (2%) and maturity (2.4%), suggesting potential adaptability to water-limited environments. Giza 126 maintained the highest root lengths and had the highest stomatal conductance. Giza 138 consistently had the highest chlorophyll content, with SPAD values decreasing to 79% under drought. Despite leading in shoot length, Giza 135 decreased to 42.59% under drought stress. In conclusion, Giza 126 and Giza 138 showed adaptability to water-limited conditions with minimal impact on phenological traits. Giza 126 had the longest roots and highest stomatal conductance, while Giza 138 consistently maintained a high chlorophyll content. Together, they and Giza 134 are valuable for breeding programs to improve barley drought tolerance.

Phenology and morphological traits of wild crucifers impacting host selection and population build up by mustard aphid [Lipaphis erysimi (Kaltenbach)

Phenology and morphological traits of wild crucifers impacting host selection and population build up by mustard aphid [Lipaphis erysimi (Kaltenbach)

Effect of Seaweed Extract and Humic Acid Treatment on the Phenological and Yield Characteristics of Guava (Psidium guajava L.)

Aim: The main aim of this study was to evaluate the impact of seaweed and humic acid treatment at different doses on the phenological characteristics and yield of guava. Study Design: Randomized block design. Place and Duration of Study: A field experiment was conducted from December 2023 to July 2024 to assess the impact of bio-stimulants on the phenological and yield traits of guava (var. Arka Kiran) in the Poongunam village, Chengalpattu Dist, Tamil Nadu, India. Methodology: The experiment followed a Randomized Block Design with eight treatments: T₁ - Absolute control, T₂ - Water Spray, T₃ - 1% Seaweed Extract, T₄ - 1.5% Seaweed Extract, T₅ - 2% Seaweed Extract, T₆ - 1% Humic Acid, T₇ - 1.5% Humic Acid, and T₈ - 2% Humic Acid, each replicated three times. Results: Results showed that 2% Seaweed Extract (T₅) significantly improved flower retention (7.55 flowers per shoot), reduced the duration from flowering to fruit set (12.47 days), and shortened the time from fruit set to harvest (121.56 days). T₅ also led to the highest fruit set (68.65%), lowest fruit drop (48.72%), largest fruit weight (150.02 g), and greatest yield (13.35 kg/tree). Humic Acid at 2% (T₈) also improved fruit set (64.32%), fruit drop (49.54%), and yield (12.34 kg/tree), but was less effective than Seaweed Extract. Conclusion: This study demonstrates the potential of Seaweed Extract as a powerful bio-stimulant to enhance guava production, offering a sustainable alternative to traditional chemical treatments.

Definition of reproductive structures in Eucalyptus for phenological data collection.

In an era where global climate change is shifting plant phenology, global meta-analyses of multiple species are required more than ever. Common language or references for enhanced data compatibility are key for such analyses. Although the Plant Phenology Ontology (PPO) addresses this challenge, it does not capture several relevant reproductive structures that are critical in species with long reproductive cycles, like many Eucalyptus species. We reviewed the terminology and concepts that describe reproductive structures in eucalypts and compared them with the existing classes of the PPO to explore the PPO's potential for harmonizing disparate eucalypt datasets. We identified incongruencies within and between eucalypt terminology and the PPO. We tested the sensitivity of the PPO for capturing key eucalypt phenological structures and found it sensitive to classification of certain structures. To address these limitations, we developed the Eucalyptus Phenology Ontology (EPO), a new ontology that builds on the PPO and captures key reproductive structures using a more refined classification. The EPO integrates the relationships between reproductive structures, phenological stages, and phenological traits. The vocabulary is species-neutral so it can be applied to other taxa but specifies the synonyms and descriptions required to capture the complexity of eucalypt phenology.

Effect of fertigation scheduling and doses of NPK on growth, yield and quality of cherry tomato (Solanum lycopersicum L. var. cerasiforme) under protected condition

This study investigated the impact of different fertigation schedules on cherry tomato (Solanum lycopersicum var. cerasiforme) cultivation in a controlled environment at TNAU, Coimbatore, India. A Completely Randomized Design with nine treatments and three replications was used, incorporating various combinations of soil application and fertigation with water-soluble fertilizers at 25%, 50%, 75%, and 100% of the recommended dose of fertilizer (RDF). Critical parameters such as growth, phenological traits, yield, fruit quality, soil nutrient status, and plant nutrient uptake were evaluated. Statistical analyses, including ANOVA, path coefficient analysis, and principal component analysis (PCA), were performed to assess treatment effects and identify relationships between variables. The results consistently demonstrated that fertigation with water-soluble fertilizers at 100% RDF (T3) yielded the best outcomes for most parameters, followed by 75% RDF fertigation (T4) and a combination of 25% soil application and 75% fertigation (T7). Significant improvements in plant growth, yield and fruit quality were observed with optimized fertigation compared to traditional soil application methods. T3 (100% RDF through fertigation) resulted in the highest plant height (263.95 cm), number of primary branches (15), leaf area (316.77 cm²) and dry matter production (96.85 kg/plant). Yield attributes such as fruits per plant (326.50), fruit weight (3.73 g), and total yield (23.95 t/ha) were also highest in T3. Path coefficient analysis indicated strong positive correlations between growth and yield parameters. PCA showed that the first principal component accounted for 85.9 % of the total variation. These findings highlight the potential for fertigation to improve resource use efficiency and productivity in cherry tomato cultivation.

Plant phenology predicts the stability of primary production in three ecosystems of the northern Chihuahuan Desert

Abstract The temporal stability of plant productivity affects species' access to resources, exposure to stressors and strength of interactions with other species in the community, including support to the food web. The magnitude of temporal stability depends on how a species allocates resources among tissues and across phenological stages, such as vegetative growth versus reproduction. Understanding how plant phenological traits correlate with the long‐term stability of plant biomass is particularly important in highly variable ecosystems, such as drylands. We evaluated whether phenological traits predict the temporal stability of plant species productivity by correlating 18 years of monthly phenology observations with biannual estimates of above‐ground plant biomass for 98 plant species from semi‐arid drylands. We then paired these phenological traits with potential climate drivers to identify abiotic contexts that favour specific phenological strategies among plant species. Phenological traits predicted the stability of plant species above‐ground biomass. Plant species with longer vegetative phenophases not only had more stable biomass production over time but also failed to fruit in a greater proportion of years, indicating a growth–reproduction trade‐off. Earlier leaf‐out dates, longer fruiting duration and longer time lags between leaf and fruit production also predicted greater temporal stability. Species with stability‐promoting traits began greening in drier conditions than their unstable counterparts and experienced unexpectedly greater exposure to climate stress, indicated by the wider range of temperatures and precipitation experienced during biologically active periods. Our results suggest that bet‐hedging strategies that spread resource acquisition and reproduction over long time periods help to stabilize plant species productivity in variable environments, such as drylands. Read the free Plain Language Summary for this article on the Journal blog.

Breeding of new kiwifruit (Actinidia chinensis) cultivars with yellow (golden) fleshed and superior characteristics

The most widely cultivated species globally is Actinidia deliciosa cv. ‘Hayward’. However, in recent years, consumers have shown greater demand for new varieties with novel flesh colour, flavour and appearance in international markets. To meet these expectations, one breeding study was started in 2016 at the University of Guilan in Iran to develop new kiwifruit cultivars with superior characteristics. In this breeding program, 201 female and 534 male hybrid genotypes were obtained from combinations of six different parents using the controlled cross-breeding technique. The evaluations were carried out over three consecutive stages. In the first stage, 201 female hybrid genotypes and control (‘Golden’) were evaluated based on 25 phenological and pomological traits. In the second stage, hybrids passed the desired threshold values in 7 key attributes were selected. Sensory testing in the next stage evaluated these selected hybrid genotypes more. As a result of the first stage, 30 hybrid genotypes with fruit weight (90 ≥ g) were selected. Then, in the second stage, 21 hybrids that showed acceptable dry matter, hue angle, flesh firmness, soluble solid content, acidity, and ascorbic acid were selected. Finally, 13 hybrid genotypes received high scores in sensory testing, and just two hybrid genotypes represented a 100% of novelty with positive texture. These genotypes were selected as potential cultivar candidates. In future studies, fruit yield, disease/pest resistance, and post-harvest performance trials of the 13 selected candidates will be evaluated at different sites. Thus, the ones that give the best results will be introduced to kiwifruit growers.

Genotype-by-environment interaction in Dutch elm disease resistance

Dutch elm disease (DED) is a devastating forest disease. Recently, the deployment of native resistant cultivars has prompted initiatives of elm reintroduction in Europe and North America. It is known that DED resistance varies with the tree genotype and is influenced by climatic factors. However, genotype-by-environment interactions in DED resistance remain largely unexplored. In this work, we examined whether there is genetic variation in DED resistance plasticity and the roles of tree growth, phenology and anatomical traits in plastic responses. We established two experimental plots with 12 Ulmus minor genotypes in two environmentally contrasting locations in Spain: Madrid, under an inland continental climate, and Valencia, under a coastal Mediterranean climate. We monitored growth and phenology detecting high plasticity in both traits. In the inland plot, genotypes were taller and showed a more synchronized phenology than in the coast. A first DED-pathogen inoculation was carried out 45 days after the average flushing date in each location, after which trees exhibited more symptoms inland. A second inoculation was carried out by dividing the coastal plot trees into early and late flushing trees and inoculating each group at 45 days after its average flushing date. Therein, susceptibility rose to a level close to the inland plot. In both inoculations, we detected a significant genotype-by-location interaction in DED resistance. The xylem anatomy revealed high plasticity and a significant genotype-by-location interaction in most traits. In the coastal trial, trees formed narrower vessels and stored more starch before inoculation. The synchrony of leaf phenology, higher growth rate, lower starch reserves and higher structural vulnerability of earlywood to DED possibly favored susceptibility in the inland plot. The varying responses of genotypes in phenology, growth and anatomy at both locations were likely related to the differences in DED resistance, which can have important consequences for elm reintroduction.

Phenological traits and photosynthetic pigments interfere in preference and biological fitness of Chilo partellus (Swinhoe) in diverse maize lines

Phenological traits and photosynthetic pigments interfere in preference and biological fitness of Chilo partellus (Swinhoe) in diverse maize lines

Genetic loci associated with sorghum drought tolerance in multiple environments and their sensitivity to environmental covariables.

Climate change can limit yields of naturally resilient crops, like sorghum, challenging global food security. Agriculture under an erratic climate requires tapping into a reservoir of flexible adaptive loci that can lead to lasting yield stability under multiple abiotic stress conditions. Domesticated in the hot and dry regions of Africa, sorghum is considered a harsh crop, which is adapted to important stress factors closely related to climate change. To investigate the genetic basis of drought stress adaptation in sorghum, we used a multi-environment multi-locus genome-wide association study (MEML-GWAS) in a subset of a diverse sorghum association panel (SAP) phenotyped for performance both under well-watered and water stress conditions. We selected environments in Brazil that foreshadow agriculture where both drought and temperature stresses coincide as in many tropical agricultural frontiers. Drought reduced average grain yield (Gy) by up to 50% and also affected flowering time (Ft) and plant height (Ph). We found 15 markers associated with Gy on all sorghum chromosomes except for chromosomes 7 and 9, in addition to loci associated with phenology traits. Loci associated with Gy strongly interacted with the environment in a complex way, while loci associated with phenology traits were less affected by G × E. Studying environmental covariables potentially underpinning G × E, increases in relative humidity and evapotranspiration favored and disfavored grain yield, respectively. High temperatures influenced G × E and reduced sorghum yields, with a ~ 100kgha-1 average decrease in grain yield for each unit increase in maximum temperature between 29 and 38°C. Extreme G × E for sorghum stress resilience poses an additional challenge to breed crops for moving, erratic weather conditions.

Correlation and Path Coefficient Analysis for Yield and its Phenological, Physiological, Morphological and Biochemical Traits under 60 mM Salinity Stress in Chickpea (Cicer arietinum L.)

The investigation was carried out during rabi season (November–April) of 2020–2021 in the polyhouse, Department of Genetics and Plant Breeding, Lovely Professional University, Phagwara, Punjab, India to assess the performance of chickpea genotypes under salinity stress conditions. The experiment was conducted using a Completely Randomized Design (CRD) with three replications under two conditions: saline (pots without holes) and control (pots with holes). Twenty genotypes were collected out of which seventeen from ICRISAT, Hyderabad and three from ARS, SriGanganagar. The salinity stress was created using salts NaCl, which were administered in split doses of 60 mM at the time of sowing and 15 DAS. The study monitored various parameters such as phenological, physiological, morphological, biochemical, and yield parameters to determine the effect of salt stress on genotypes exhibiting different tolerance levels. The results showed that the total proline content increased due to the production of stress-related proteins during salinity stress. However, the yield parameters were reduced under stress conditions, with the highest decrease observed in the 60 mM NaCl treatment group compared to the control group. Based on the results of the study, ICC5439 and GNG 1581 are highly tolerant chickpea genotypes under salinity stress conditions. ICC 6050, ICC 251, ICC 252, and ICC 262 are medium tolerant genotypes, while ICC253, ICC 247, and ICC 249 are highly susceptible genotypes. Remaining are minimum tolerant and sensitive genotypes.

Difference in reproductive traits of two sympatric species of Stigmaphyllon (Malpighiaceae) throughout their distribution range: Are they context-dependent?

Populations of widely distributed plants may experience varying climatic or ecological conditions, leading to uneven evolution of reproductive traits. However, studies on reproductive biology usually focus on just one, or rarely two, sampling areas. In this study, we performed a geographical comparative analysis of the flowering pattern, pollination biology and breeding system of Stigmaphyllon bonariense and S. jatrophifolium (Malpighiaceae) throughout their natural distribution in Argentina, classifying them as ‘northern’ or ‘southern’ according to their geographic location. For this, we selected 4 populations for S. bonariense and 3 for S. jatrophifolium to characterized the flowering peak at both the individual (IFP) and population (PFP) levels, the floral display per inflorescence, the richness of Malpighiaceae species and their pollinators, and the stigmatic and body pollen loads of the pollinators. In addition, we performed manipulative experiments to determine the breeding system. Our results showed that the duration of flowering phenology and the floral display vary between northern and southern populations of both species. These traits include flowering duration and the number of flowers at anthesis per inflorescence (floral display). In addition, the pollination context exhibited latitudinal differences in species richness, phenology, body size of oil-collecting bees, and visitation frequency. Besides, the number of co-flowering Malpighiaceae species varied among populations. However, no considerable differences were observed among populations in terms of stigmatic and body pollen load in pollinators of both species. The breeding system was invariable and consistent in both species with self-incompatibility (SI). These findings suggest that certain reproductive traits of both Stigmaphyllon species are context-dependent and would allow the species maximise reproductive success in each population. Therefore, our results demonstrate that large-scale geographical studies (i.e., several populations with different climatic conditions) and the analysis of various phenological traits are necessary to better understand the reproductive biology of plant species.

Editorial: The adaptation, plasticity and extinction of forest plants to climate change: mechanisms behind the morphological, physiological, phenological and ecological traits

Editorial: The adaptation, plasticity and extinction of forest plants to climate change: mechanisms behind the morphological, physiological, phenological and ecological traits

Development of a methodology for assessing economically useful signs of hyssop

Hyssop (Hyssopus officinalis L.) refers to valuable spicy-aromatic, essential oil and medicinal crops and is widely used in traditional and folk medicine, perfumery, cosmetology, cooking and food industry. The main directions of selection of hyssop are increasing productivity, obtaining forms adapted to industrial cultivation technology, resistance to pests and diseases, valuable chemical and biochemical composition, different terms of onset of economic suitability, honey productivity, zoning (suitability for cultivation in specific soil and climatic conditions). The article presents the results of studies on the evaluation of the breeding material of hyssop by a complex of economically useful morphological, morphometric and phenological traits, including a new zoned author’s variety of the Belarusian State Agricultural Academy Zaveya. As a result of the research, the methodology for testing the distinctiveness, uniformity and stability of hyssop has been improved, which makes it possible to optimize the breeding process of this crop and conduct an extended assessment of the identification of varieties during state variety testing. The national methodology for testing for distinctiveness, uniformity and stability provides an opportunity for breeders to pay attention to the relevant characteristic and distinctive features of hyssop, which will contribute to the effective conduct of further breeding work to create forms and varieties with various economically valuable properties.

Assessment of genetic diversity by phenological traits, field performance, and Start Codon Targeted (SCoT) polymorphism marker of seventeen soybean genotypes (Glycine max L.).

The Egyptian-farmed soybeans have a wide range of genetic diversity which is most important in plant improvement programs in order to develop new higher yielding soybean genotypes. The present study is designed to determine the genetic variability among seventeen genotypes of cultivated soybean (Glycine max L.) by examining the phenotypic level at the seedling stage, field performance over two years 2022/2023 and genetically using Start Codon Targeted (SCoT) markers. Results indicated that the SCoT markers, 100 seed weight, and tip angle (TA) traits were positively correlated with H2L12, DR 101, H15L5, and H117 genotypes. In addition, the number of branches per plant and plant height were associated with H113, H32, Crowford, H129, and D7512035. Furthermore, the length of the first internode (LFI), root width (RW), root length (RL), and shoot length (SL) were more associated with Giza 111, NC105, and Hutcheson. The hierarchical cluster analysis (HCA) and its associated heatmap explored the differences among the genotypes. It showed that all examined parameters were clustered into four distinct clusters. The obtained results showed that genotypes NC105, H30, D75_12035, and H2L12 have promising phenological and morphological traits besides tracking the inheritance of nearby genes surrounding the ATG translation start codon since they are in a monoclades. The obtained results will help the breeder plan appropriate selection strategies for improving seed yield in soybeans through hybridization from divergent clusters.

Effects of Root Pruning and Size on Growth Traits of Hybrid Poplar Seedlings

Selecting seedlings of varying sizes and effectively managing root pruning are key challenges in transplantation. However, the effects of seedling size and root pruning on transplantation outcomes are not fully understood. This study classified one-year-old Populus ‘Beilinxiongzhu-01’ seedlings into three size categories based on height: large (308.75 ± 9.66 cm), medium (238.00 ± 7.71 cm), and small (138.92 ± 7.18 cm). In early March of the subsequent year, root pruning was applied with varying intensities based on root collar diameter: low (15 times), medium (7.5 times), and high (3.75 times). A control group without pruning was also included. Over the year, key phenological and morphological traits were monitored. The results showed that (1) root pruning significantly impacted the phenology of seedlings, accelerating root emergence, delaying early leaf phenology, increasing the dieback rate, and postponing end-of-season defoliation. Mortality and the rapid growth phase were not significantly affected. Larger seedlings exhibited earlier end-of-season defoliation and higher dieback rates early in the growing season, while smaller seedlings advanced in early leaf development. (2) Except under low or no pruning, root pruning reduced seedling height (H), diameter at breast height (DBH), and root collar diameter (RCD). However, across all treatments, these indicators remained higher in larger seedlings compared to smaller ones. Under medium- and high-intensity pruning, smaller seedlings exhibited higher relative growth rates and larger leaf areas than larger seedlings, with the reduction in these variables becoming more pronounced as seedlings increased in size. Notably, only larger seedlings demonstrated a reduction in maximum growth rate, suggesting greater vulnerability to root pruning. In summary, root pruning induced significant phenological and morphological differences across seedling sizes. While smaller seedlings showed some response to pruning, larger seedlings experienced more pronounced phenological disruptions and growth inhibition.

Plant community responses to the individual and interactive effects of warming and herbivory across multiple years.

Anthropogenic climate warming affects plant communities by changing community structure and function. Studies on climate warming have primarily focused on individual effects of warming, but the interactive effects of warming with biotic factors could be at least as important in community responses to climate change. In addition, climate change experiments spanning multiple years are necessary to capture interannual variability and detect the influence of these effects within ecological communities. Our study explores the individual and interactive effects of warming and insect herbivory on plant traits and community responses within a 7-year warming and herbivory manipulation experiment in two early successional plant communities in Michigan, USA. We find stronger support for the individual effects of both warming and herbivory on multiple plant morphological and phenological traits; only the timing of plant green-up and seed set demonstrated an interactive effect between warming and herbivory. With herbivory, warming advanced green-up, but with reduced herbivory, there was no significant effect of warming. In contrast, warming increased plant biomass, but the effect of warming on biomass did not depend upon the level of insect herbivores. We found that these treatments had stronger effects in some years than others, highlighting the need for multiyear experiments. This study demonstrates that warming and herbivory can have strong direct effects on plant communities, but that their interactive effects are limited in these early successional systems. Because the strength and direction of these effects can vary by ecological context, it is still advisable to include levels of biotic interactions, multiple traits and years, and community type when studying climate change effects on plants and their communities.

Seasonally Changing Interactions of Species Traits of Termites and Trees Promote Complementarity in Coarse Wood Decomposition.

Complementary resource use by functionally different species may accelerate ecosystem processes. However, how co-variation in plant traits and animal traits promotes complementarity through temporal plant-animal interactions is poorly understood, even less so in detrital systems, thereby hampering our fundamental understanding of decomposition and carbon turnover. We hypothesised that, in seasonal subtropical forests where termites are major deadwood decomposers, trait complementarity of both termite species and tree species should promote overall deadwood decomposition through different seasons and years. Findings from a four-year coarse wood decomposition experiment involving 27 tree and 5 termite species support this hypothesis. Phenological and mandibular traits of the two most abundant termite species controlled wood decomposition of tree species differing in wood traits, through the seasons over 4 years, thereby promoting overall deadwood decomposition rates. Our findings indicate that complementarity in functional trait co-variation in plants and animals plays an important role in carbon cycling.

Toward a Functional Trait Approach to Bee Ecology.

Functional traits offer an informative framework for understanding ecosystem functioning and responses to global change. Trait data are abundant in the literature, yet many communities of practice lack data standards for trait measurement and data sharing, hindering data reuse that could reveal large-scale patterns in functional and evolutionary ecology. Here, we present a roadmap toward community data standards for trait-based research on bees, including a protocol for effective trait data sharing. We also review the state of bee functional trait research, highlighting common measurement approaches and knowledge gaps. These studies were overwhelmingly situated in agroecosystems and focused predominantly on morphological and behavioral traits, while phenological and physiological traits were infrequently measured. Studies investigating climate change effects were also uncommon. Along with our review, we present an aggregated morphological trait dataset compiled from our focal studies, representing more than 1600 bee species globally and serving as a template for standardized bee trait data presentation. We highlight obstacles to harmonizing this trait data, especially ambiguity in trait classes, methodology, and sampling metadata. Our framework for trait data sharing leverages common data standards to resolve these ambiguities and ensure interoperability between datasets, promoting accessibility and usability of trait data to advance bee ecological research.

Combining ability for grain yield and low-N tolerance of intermediate/late maturing maize (Zea mays) inbred lines

ABSTRACT Low soil nitrogen (N) is a significant challenge to maize (Zea mays L.) production in Sub-Saharan Africa, particularly for small-scale farmers. Developing maize hybrids tolerant to low N is crucial for improving yields under such conditions. This study examined the genetic basis of agronomic traits in intermediate/late maturing maize inbred lines under contrasting N conditions, focusing on general combining ability (GCA) and specific combining ability (SCA) effects. Two hundred and thirty-seven F1 hybrids from 79 inbred lines crossed with three testers in a line x tester mating design, were evaluated across eight environments in Nigeria. Line x tester analysis revealed that GCA effects, primarily from lines, predominantly influenced grain yield and other traits across both N conditions, except for ear height and plant aspect under low N, where SCA effects also had significant impact. A significant (p ≤ 0.01) positive correlation was observed between GCA and SCA effects, suggesting a positive relationship between additive and non-additive genetic components. Lines SMLW146 and SMLW147 were identified as valuable resources for breeding low-N tolerant hybrids. Additionally, considering non-additive effects, hybrids SMLW22 × SAM50M and SMLW106 × SAM50M (under low-N) and SMLW3 × IITA1876, SMLW84 × IITA1876, and SMLW165 × IITA1876 (under optimum-N) were promising combinations for high grain yield. Morphological traits like plant height and ear height, phenological traits like days to anthesis and silking, and qualitative traits like ear aspect and plant aspect were identified as important for selecting genotypes with improved grain yield under low-N conditions.