Number Of Kernels Research Articles

Determining adaptability of farmer bred spring wheat (Triticum aestivum L.) genotypes to Canadian organic production using stability analysis

AbstractParticipatory plant breeding (PPB) is a collaborative process between farmers, plant breeders and researchers to create germplasm specifically bred for target environments. We sought to examine the yield performance and adaptability of genotypes from an organic PPB wheat programme under organic management across the Canadian prairies. We evaluated 25 farmer genotypes and 6 commercial cultivars in locations in Alberta, Saskatchewan and Manitoba, totalling 12 organic environments. The top performers most responsive to higher yield environments were three farmer genotypes (BL34‐SW, BL43C‐TM and BJ13‐GW) and one check cultivar (Vesper). Genotype plus genotype by environment (GGE) biplot analysis indicated that one farmer genotype (BL23‐AS) and one check cultivar (Vesper) demonstrated high yield and greater organic adaptation than other genotypes tested. Two registered cultivars (AAC Brandon and Jake) had low yield and poor adaptation, as did one farmer genotype (PWA10B‐LD). Yield was positively and strongly correlated with height, anthesis and mature biomass and kernel number per unit area. The results provide evidence that early generation farmer selection is an effective breeding strategy for discovering wheat genotypes with high yield and excellent adaptability to organic production systems in Canada.

Molecular Diversity and Combining Ability in Newly Developed Maize Inbred Lines under Low-Nitrogen Conditions.

Nitrogen is an essential element for maize growth, but excessive application can lead to various environmental and ecological issues, including water pollution, air pollution, greenhouse gas emissions, and biodiversity loss. Hence, developing maize hybrids resilient to low-N conditions is vital for sustainable agriculture, particularly in nitrogen-deficient soils. Combining ability and genetic relationships among parental lines is crucial for breeding superior hybrids under diverse nitrogen levels. This study aimed to assess the genetic diversity of maize inbred lines using simple sequence repeat (SSR) markers and evaluate their combining ability to identify superior hybrids under low-N and recommended conditions. Local and exotic inbred lines were genotyped using SSR markers, revealing substantial genetic variation with high gene diversity (He = 0.60), moderate polymorphism information content (PIC = 0.54), and an average of 3.64 alleles per locus. Twenty-one F1 hybrids were generated through a diallel mating design using these diverse lines. These hybrids and a high yielding commercial check (SC-131) were field-tested under low-N and recommended N conditions. Significant variations (p < 0.01) were observed among nitrogen levels, hybrids, and their interaction for all recorded traits. Additive genetic variances predominated over non-additive genetic variances for grain yield and most traits. Inbred IL3 emerged as an effective combiner for developing early maturing genotypes with lower ear placement. Additionally, inbreds IL1, IL2, and IL3 showed promise as superior combiners for enhancing grain yield and related traits under both low-N and recommended conditions. Notably, hybrids IL1×IL4, IL2×IL5, IL2×IL6, and IL5×IL7 exhibited specific combining abilities for increasing grain yield and associated traits under low-N stress conditions. Furthermore, strong positive associations were identified between grain yield and specific traits like plant height, ear length, number of rows per ear, and number of kernels per row. Due to their straightforward measurability, these relationships underscore the potential of using these traits as proxies for indirect selection in early breeding generations, particularly under low-N stress. This research contributes to breeding nitrogen-efficient maize hybrids and advances our understanding of the genetic foundations for tolerance to nitrogen limitations.

Potassium Management for Corn Growth, Yield and Sweetness under Sabah Sandy Soil

A study was conducted to determine the effect of potassium (K) with organic fertilizers on the growth, yield and sweetness of reddish waxy corn. The treatments were: (T1) standard fertilizer rate of 60 kg ha-1 K2O without organic fertilizer (control); (T2) 30 kg ha-1 K with organic fertilizer; (T3) 90 kg ha-1 K with organic fertilizer and (T4) 120 kg ha-1 K with organic fertilizer. Organic fertilizer used was 1.5 t ha-1 Bokashi and 20 t ha-1 chicken manure biochar (CMB). The planted corn received 120 kg ha-1 N and 60 kg ha-1 P2O5. The experimental design was Completely Randomized Design (CRD) with six replications. Stem girth, number of leaves, the height of the first cob, fresh weight of the first cob, 100 grains weight, cob girth, cob length and sweetness (Brix scale, %) data were analyzed using ANOVA (Analysis of Variance) at 5% significant levels. The Least Significant Different (LSD) was used to compare the means for significantly different results. Significant differences in growth were obtained at (p&lt;0.05) in waxy corn for the number of leaves, the height of the first cob, length of cob, and girth between the control and all treatments. However, there is no significant difference for the sweetness of waxy corn for all treatments. Mean total for growth parameters; the number of leaves, stem girth and height of the first cob from soil surfaces and mean total for yield parameters; cob girth, length of cob, fresh weight of cob, 100 grains weight and the number of kernels was significantly higher for all treatments of T2, T3 and T4 compared to control the treatment of T1. The study showed no significant difference in the sweetness of waxy corn with increasing potassium application, resulting in increased total soluble content. Similar studies for a different rate of organic fertilizers and soil analysis can be done to ascertain further the effects on growth, yield, and sweetness parameters of reddish waxy corn with selected soil properties.

Moderately reducing N input to mitigate heat stress in maize

In a warming climate, high temperature stress greatly threatens crop yields. Maize is critical to food security, but frequent extreme heat events coincide temporally and spatially with the period of kernel number determination (e.g., flowering stage), greatly limiting maize yields. In this context, how to increase or at least maintain maize yield has become more important. Nitrogen fertilizer (N) is widely used to improve maize yields, but its effect in heat stress is unclear. For this, we collected 1536 pairs of comparisons from 113 studies concerning N conducted in the past 20 years over China. We classified the data into two groups – without high temperature stress (NHT) and with high temperature stress during the critical period for maize kernel number determination (HT) – based on the national meteorological data. We comprehensively evaluated N effects on grain yield under HT and NHT using meta-analysis. The effect of N on maize yield became significantly smaller in HT than that in NHT. In NHT, soil characteristics, crop management practices, and climatic conditions all significantly affected N effects on maize yield, but in HT, only a few factors such as soil organic matter and mean annual precipitation significantly affected N effects. Hence, it is difficult to improve N effect by improving soil characteristics and crop management when meeting with high temperature stress during flowering. On average, N effect increased with increased N input, but there were respective N input thresholds in NHT and HT, beyond which N effects on maize yield remained stable. According to the thresholds, it is speculated that moderately reducing N input (~20 %) likely increased high temperature tolerance of maize during flowering. These findings have important implications for the optimization of N management under a warming climate.

A rapid monitoring protocol to estimate unharvested corn biomass in waterfowl impoundments

AbstractConservation planners use bioenergetic models to develop habitat objectives that satisfy energetic demands of waterfowl during nonbreeding periods. In turn, natural resource managers should estimate yield and availability of natural and cultivated waterfowl forage to monitor contributions to objectives and support adaptive resource management. Because bioenergetic models are particularly sensitive to unharvested flooded croplands, we developed a rapid methodology to estimate biomass of unharvested flooded corn (Zea mays) and tested our methodology in impounded corn fields planted and flooded in western Tennessee during autumn and winter of 2019–2021. We evaluated accuracy of our rapid assessment method and conducted simulations to assess variance‐bias trade‐offs relative to sample size. Rapid assessments lasted 20 min ± 10 minutes per field. Our rapid assessment method underestimated number of kernels per ear by 2.6% ± 0.5%. After adjusting for underestimation bias, corn biomass across all surveys was 5,500 kg/ha ± 250 kg/ha, which is similar yield to previous literature from waterfowl impoundment fields. Sampling 15 ears per field allowed field biomass to be estimated within acceptable accuracy (i.e., variance [SE] of mean percent error &lt;1.8%). We recommend our rapid yield assessment method be incorporated into habitat monitoring protocols to efficiently and precisely estimate corn biomass for improved conservation planning initiatives. Additionally, our rapid assessment method allows managers to monitor field yield rapidly, enabling estimates of corn depletion and availability throughout the nonbreeding season for waterfowl to support management decisions.

Adaptation to priming drought at six-leaf stage relieves maize yield loss to individual and combined drought and heat stressors around flowering

The frequency and magnitude of drought and heat events are predicted to increase, exerting adverse effects on maize yield. Repeated stress events may lead to critical stage or process shifts in maize yield response, but few studies document such shifts. In this experiment, maize plants were exposed to drought at the six-leaf period (V6) to investigate the priming effects on maize yield formation under control (CK), drought stress (DS), heat stress (HS), and combined drought and heat stress (DHS) occurring around flowering (AF). The stressors was significantly reduced maize yield by 10.0%–41.4% compared with T1 (V6CK+AFCK), with the exception of the T5 (V6DS+AFCK) treatment. Fortunately, compared with T1 (V6CK+AFCK), T2 (V6CK+AFDS), T3 (V6CK+AFHS), and T4 (V6CK+AFDHS) treatments around flowering, exposure to drought at V6 improved yield by 6.4%, 11.1%, 2.6%, and 33.4%, respectively. The increased yield in stressors around flowering was attributed to the enhancement of kernel numbers (KNS) and kernel weight (KW). However, KNS and KW showed variable responses to treatments. Drought exposure at V6 relieved KNS loss without stressors around flowering, as the fertilized florets increased by 2.7%. The KNS loss in DS and DHS treatment around flowering was reversed via seed setting, increased by 6.0% and 7.4%, resulting from strengthened sugar-starch conversion. Furthermore, the reduced KW in HS and DHS treatment around flowering was improved due to increased starch synthesis ability during kernel filling. Consequently, drought priming at the V6 stage increased seed setting, sugar-starch conversion, and starch synthesis ability, improving KNS and KW, offering a method to relieve yield loss under stressors around flowering.

Appropriate seed source and rate enhanced the productivity of bread wheat varieties under irrigated conditions in North Mecha, Amhara region, Ethiopia

Bread wheat is a strategic cereal crop produced ndederunder both irrigation and main rainy season in the Amhara region, Ethiopia. However, its productivity is low due to unreliable seed sources, inappropriate seed rate, and unavailability of adaptable improved varieties for a wide range of agro-ecologies. Therefore, an experiment aimed at evaluating the influence of seed sources, rates, and varieties on yield and yield-related traits under irrigated conditions was conducted during 2021 at North Mecha, Amhara region, Ethiopia, to provide information and knowledge for bread wheat researchers and producers. The experiment was laid out in a randomized complete block design with three replications in a factorial arrangement of two varieties (Kakaba and Ogolcho), three seed sources (Ethiopia Seed Enterprise (ESE), Ediget Bandinet Seed Producing Cooperative Union (EBSPCU), and farmers with three seed rates (125, 150, and 175 kg ha-1). Basic agronomic and yield data were collected. The data were analyzed using SAS software. The results showed that productive tiller numbers, 50 % heading, number of kernels per spike, and plant height were significantly influenced by the interaction of seed source with variety. Interaction of variety with seed rate had also significantly influenced productive tiller number and 50 % heading. The highest grain yield (4.99 t/ha) was recorded on Kakaba variety sourced from Ediget Bandinet seed producing union sown at a rate of 150 kg ha−1 followed by Ethiopia seed enterprise (4.31 t ha−1) sown at the same seed rate. Kakaba seeds sourced from farmers produced the least grain yield. Therefore, using Kakaba seeds from the formal seed system like Edget Bandinet seed producing union sown at a rate of 150 kg ha−1 could be recommended to increase the productivity of bread wheat under irrigated condition in north Mecha. It is also necessary to conduct experiments considering a greater number of seed sources, seed rates, and varieties in more than one cropping season and location to strengthen the current result.

Comprehending flame development and misfire at advanced engine conditions: Detailed experimental characterizations and machine learning-assisted kinetic analyses

Through comprehensive experimental and modeling efforts, this work unravels the underlying mechanisms governing flame development and misfire at advanced engine conditions that are representative of low-load and lean blow-out operations. Toward this, preliminary heat release, autoignition, and flame developing patterns are characterized, via a case study of n-heptane, at ultra-lean conditions in a well-controlled optical engine under various combustion modes including homogeneous charge compression ignition (HCCI), partially premixed combustion (PPC), and reactivity-controlled compression ignition (RCCI). Changes in preliminary heat release and flame developing patterns at three overall equivalence ratios (0.12, 0.18, and 0.24) are first characterized under the PPC mode. Flame development characteristics including flame areas and number of initial flame kernels at close-to-misfire conditions are further extracted and compared across the HCCI, RCCI, and three PPC modes, with two distinctive and one transition regimes identified. Further analyses indicate that sustainable flame development and misfire are largely controlled by the spatial distribution of local equivalence ratio (phi) and local temperature in the mixture, which dictate the initial flame kernel generation and the subsequent flame propagation through localized preliminary heat release and autoignition. Chemical kinetic modeling is also undertaken, using a recently updated gasoline chemistry model, in conjunction with a backpropagation neural network, where the predicted ignition delay map well captures the different regions of flame development. Further kinetic analysis and heat rate of production per reaction analysis corroborate the CH2O planar laser-induced fluorescence experiments and highlight the important chemical kinetics that govern the initial flame development patterns.

Assessment of Variability, Heritability and Genetic Advance in Groundnut (Arachis hypogaea L.)

The present research, entitled “Assessment of Variability, Heritability, and Genetic Advance in Groundnut (Arachis hypogaea L.),” was conducted on 15 genotypes with 16 characteristics. The analysis of variance revealed that genotypic variation was extremely significant for all of the traits under consideration. Additionally, the phenotypic coefficient of variance was larger than the genotypic coefficient of variation in magnitude. Quantitative features include the number of pods and kernels per plant, days to bloom initiation, days to 50% flowering, and days to maturity, test weight, shelling percent, and kernel yield per plant showed high heritability indicating that the variation was caused by additive gene action. The correlation estimates provide a better understanding of yield components and studies on genotypic and phenotypic correlation coefficients of different traits help the plant breeder during selection.

Nitrogen deficiency in maize fields of the Southern Pampas does not affect kernel number but reduces weight per kernel.

Nitrogen (N) requirement of maize has been increasing over the past decades, but there has been a lack of adjustment in fertilization management practices across different regions in Argentina. The higher N requirement in modern hybrids is associated with a higher post-flowering N accumulation. Additionally, soil fertility in the Argentina Pampas has consistently decreased in recent years. Whether the effects of N deficiency are expressed in the post-flowering period is still unclear at field level. The objective of this work was to quantify the yield reduction attributed to N deficiency and to identify the physiological basis of this effect at the field level for typical high-tech farms across the south-eastern Pampas of Argentina. Nineteen experiments were conducted during the 2020/2021 growing season in the south-eastern Pampas, evaluating two N managements i) Farmers' N level; ii) High N input. Results showed that the additional N input increased grain yield by an average of 6.4% (average grain yield difference of 712 kg ha−1). Weight per kernel was the only yield component that responded to N fertilization. Farmers' N management did not affect N accumulation or growth-related variables such as leaf area index, green leaves per plant, PAR interception, nitrogen sufficiency index until flowering, but the farmers' N level reduced these variables during the grain filling period leading to differences in aerial biomass and N accumulated at physiological maturity. Farmers' N level led to decreased post-flowering N uptake during grain filling period, which reduced the photosynthetic capacity of the canopy. These findings suggest that N management strategies and models need to be reviewed for high-tech maize systems.

Agro Morphological Trait and Yield Component Evaluation of Malt Barley (Hordeum Distichon L.) Varieties Response to the Rate of Fertilizer in Habro Woreda West Hararghe Zone, Oromia, Ethiopia

The study assessed the effects of NPSB Fertilizer Rate on Yield and morphological traits of Malt barley Varieties. The experiment used a Randomized Complete Block Design with three varieties and five levels of fertilizer rates. The effects of NPSB fertilizer rate and varieties were highly significant on all yield components; phenology and morphological traits. The highest number of kernels per spike (29.5), above ground biomass (12.0 tha-1), and straw yield (6.4 tha-1) were obtained from 200kg NPSB ha-1 , while highest the thousand grain weights (48.2g) were obtained from 150kg NPSB ha-1. The interaction effects of varieties and fertilizer rates were significant at p&lt;0.05 on grain yield (5653.3) from the Traveller variety at 150 kg NPSB ha-1 fertilizer rates. The analysis of variance showed that the interaction effects of varieties and fertilizer rates were significant at p&lt;0.05 on Hectoliter (69.133) from the Traveller variety at 150 kg NPSB ha-1 fertilizer rates. Finally, from the above result, it can be concluded that using 150 kg ha-1 NPSB fertilizer with Traveller variety can be recommended for malt barley production in the study area.

Photosynthetic capacity and assimilate transport of the lower canopy influence maize yield under high planting density.

Photosynthesis is a major trait of interest for the development of high-yield crop plants. However, little is known about the effects of high-density planting on photosynthetic responses at the whole-canopy level. Using the high-yielding maize (Zea mays L.) cultivars "LY66," "MC670," and "JK968," we conducted a 2-yr field experiment to assess ear development in addition to leaf characteristics and photosynthetic parameters in each canopy layer at 4 planting densities. Increased planting density promoted high grain yield and population-scale biomass accumulation despite reduced per-plant productivity. MC670 had the strongest adaptability to high-density planting conditions. A physiological analysis showed that increased planting density primarily led to decreases in the single-leaf area above the ear for LY66 and MC670 and below the ear for JK968. Furthermore, high planting density decreased chlorophyll content and the photosynthetic rate due to decreased canopy transmission, leading to severe decreases in single-plant biomass accumulation in the lower canopy. Moreover, increased planting density improved presilking biomass transfer, especially in the lower canopy. The yield showed significant positive relationships with photosynthesis and biomass in the lower canopy, demonstrating the important contributions of these leaves to grain yield under dense planting conditions. Increased planting density led to retarded ear development as a consequence of reduced glucose and fructose contents in the ears, indicating reductions in sugar transport that were associated with limited sink organ development, reduced kernel number, and yield loss. Overall, these findings highlighted the photosynthetic capacities of the lower canopy as promising targets for improving maize yield under dense planting conditions.

Genetic variability and character association among maize (Zea mays L.) Inbred lines

Genetic analysis of variability, heritability and character association was studied among 25 maize inbred lines for eleven traits. The ANOVA indicated significant variation existed among the inbred lines chosen for the study for all the traits. Wide range of variability was observed for all the traits among them grain yield varied from 16.03 to 62.52 q/ha with an average mean value of 45.75 q/ha. Phenotypic variance was higher compared to genotypic variance and highest phenotypic variance was observed for plant height followed by grain yield. However, the difference between phenotypic and genotypic variance was very narrow for majority of the traits. Similarly, phenotypic coefficient of variation (PCV) was marginally higher than genotypic coefficient of variation (GCV) and highest GCV and PCV was recorded for grain yield (37.03, 38.12) followed by ear height (24.12, 26.48) indicating that these characters are under genetic control have high potential for selection. The high amount of broad-sense heritability coupled with high genetic advance as a percent mean (GAM) was observed for grain yield (0.94 and 74.12) followed by number of kernels per row (0.90 and 32.88) indicating phenotypic based selection for these traits would be successful. Hundred grain weight had the highest genotypic correlation (0.834) with grain yield followed by number of kernels per row (0.623). Bangladesh J. Bot. 53(1): 57-65, 2024 (March)

Study on the hierarchical structure of container port systems along the South China Sea in the context of low carbon emissions

Under the low-carbon background, 37 ports of countries along the South China Sea with capacity ranking in the world’s top 100 container ports are selected as the research object to establish a shipping network, construct a directed dichotomous shipping network, and divide the port tiers after finding the kernel number by using kernel analysis method, respectively, to explore the relationship between tiers and the relationship between ports at the higher level, and then make clear the direction of the improvement for the reduction of carbon emissions. The results show that: the routes sent between container ports in countries along the South China Sea have formed a more stable connection, but the receiving routes are still in a passive position, and the port call relationship is affected by the port hierarchy. High-level ports such as Shanghai Port and Singapore Port undertake the transshipment function of cargo concentration and redistribution within the network. The small-world characteristics among ports such as Singapore Port, Ningbo Port, Haiphong Port, Shenzhen Port, Guangzhou Port, and Linchaban Port are obvious. Based on the results of the empirical analysis, corresponding suggestions are put forward to optimize the structure of the container port system in the countries along the South China Sea and promote the low-carbon development of the sea.

Multi-View Randomized Kernel Classification via Nonconvex Optimization

Multi kernel learning (MKL) is a representative supervised multi-view learning method widely applied in multi-modal and multi-view applications. MKL aims to classify data by integrating complementary information from predefined kernels. Although existing MKL methods achieve promising performance, they fail to consider the tradeoff between diversity and classification accuracy of kernels, preventing further improvement of classification performance. In this paper, we tackle this problem by generating a number of high-quality base learning kernels and selecting a kernel subset with maximum pairwise diversity and minimum generalization errors. We first formulate this idea as a nonconvex quadratic integer programming problem. Then we transform this nonconvex problem into a convex optimization problem and prove it is equivalent to a semidefinite relaxation problem, which a semidefinite-based branch-and-bound algorithm can quickly solve. Experimental results on the real-world datasets demonstrate the superiority of the proposed method. The results also show that our method works for the support vector machine (SVM) classifier and other state-of-the-art kernel classifiers.

Pollen‐mediated gene flow from herbicide‐resistant yellow corn to non‐genetically engineered food‐grade white corn

AbstractNebraska is the number one producer of food‐grade white corn in the United States. Pollen‐mediated gene flow (PMGF) from genetically engineered high alpha‐amylase corn, known as Enogen corn, to food‐grade white corn can have undesirable outcomes. Alpha‐amylase can convert starch in white corn to sugar during or after its processing, degrading the quality of processed products. Thus, proximity to Enogen corn puts white corn production at risk. The objectives of this study were to evaluate the PMGF from herbicide‐resistant yellow corn to food‐grade white corn and assess the significance of wind speed and direction. Field experiments were set up using a Nelder‐wheel design in 2021 and 2022 in Nebraska, with yellow field corn as pollen donor in the center and white corn surrounding it as pollen receptor. At the end of the season, samples of white corn cobs were collected up to 50 and 70 m from four cardinal and ordinal directions, respectively. PMGF was detected by counting the number of yellow kernels on the white cobs. More than 4 million kernels were screened and the highest frequency of PMGF (0.0621–0.1950) was detected at the nearest distance (1 m). PMGF decreased exponentially with distance; however, it was still observed (0.0020–0.0032) at the greatest distance (70 m) evaluated in this study. Wind profile played a significant role in PMGF. Wind frequency (r = 0.58 ≤ 0.86) and wind run (r = 0.36 ≤ 0.95) were moderately to strongly correlated with PMGF in 2021 and 2022, respectively. The results are concerning for white corn growers due to the coexistence of Enogen corn and food‐grade white corn.

Growth and yield of groundnut (Arachis hypogaea) under varying levels of gypsum and zinc application in Iran

A field study was carried out during spring season of 2021 and 2022 at Astaneh-ye Ashrafiyeh, Guilan, (Islamic Azad University, Lahijan, Iran) northern Iran to study the effect of natural gypsum (NG) and zinc (Zn) foliar application on peanut (Arachis hypogaea L.) yield and quality. NG was applied at 4 levels [0 (NG0); 10 (NG10); 20 (NG20); and 30 (NG30) g/m2] and Zn nano-chelates were applied at 3 levels [0 (Zn0); 1 (Zn1); and 2 (Zn2) g/L)] as foliar application. The results showed that the interaction of NG × Zn was significant for leaf chlorophyll, kernel and pod number per plant, kernel protein, oil content and and kernel yield during both the years. The interaction of NG × Zn was also significant on the P, S and Fe of kernels. Leaf K and Fe contents were significantly influenced only by NG. The comparison between mean revealed that the highest kernel yield (5839 kg/ha), kernel number (93.5 kernels/plant), pod number (66.3 pods/plant) and kernel S (0.384%) were recorded from the plots applied with NG20 + Zn2. The highest leaf chlorophyll (3.83 mg/kg FW) and oil content (46.09%) were related to the treatment NG20 + Zn1. The plots applied with NG10 + Zn2 exhibited the highest kernel protein (17.92%). Based on the results, it can be stated that the NG and Zn as soil application and foliar spray respectively, improved peanut yield and qualitative traits hence can be recommended for similar climatic conditions.

Drought stress during maize flowering may cause kernel abortion by inhibition of plasma membrane H+‐ATPase activity

AbstractBackgroundDrought stress during flowering of maize (Zea mays L.) frequently results in decreased kernel setting, leading to grain yield depressions. Plasma membrane (PM) H+‐ATPase was identified as a key enzyme responsible for supply of assimilates to the developing maize kernels shortly after pollination. The activity of this enzyme was strongly inhibited under salt stress, pointing to an involvement in kernel abortion.AimsThis study aimed to determine whether also drought stress causes inhibition of PM H+‐ATPase in developing maize kernels shortly after pollination, leading to diminished hexose uptake and finally kernel abortion. The key questions are as follows: What are the limiting factors for grain yield production of maize plants facing drought? Are physiologically relevant parameters, quantified at flowering, reflected by yield determinants at maturity?MethodsMaize plants were cultivated using the container technique, and drought stress was imposed during 3 weeks bracketing flowering compared to well‐watered conditions throughout the entire growth period. The developing kernels were harvested 2 days after pollination, and PM vesicles were isolated and purified using two‐phase partitioning.ResultsWater deficit caused a significant decrease in grain yield at maturity (−35%), which was determined by a reduced kernel number (−42%). Source limitation in the developing kernels under stress could be excluded. Acid invertase activity was unaffected by water deficit. Hexose availability was also no limiting factor for kernel setting and development. However, Vmax of in vitro hydrolytic activity of PM H+‐ATPase was significantly decreased in the developing maize kernels under drought stress and the maximal pH gradient at the PM was also significantly reduced. The observed inhibiting effects on PM H+‐ATPase were mainly of quantitative nature, as a lower number of proton pumps was present in the kernel PM. Qualitative changes of the enzyme (activation energy Ea, Michaelis constant Km) due to drought were not observed.ConclusionsThe lower pH gradient probably decreased the proton‐driven transport of hexoses by carriers into the cytosol of the kernel cells, leading to kernel starvation and eventually contributing to kernel abortion.

Fresh maize yield in response to nitrogen application rates and characteristics of nitrogen-efficient varieties

Efficient nitrogen management is crucial in developing sustainable strategies aimed at enhancing yield while mitigating negative environmental impacts. However, limited research has focused on this aspect in the production of fresh maize. Therefore, this study analyzed nitrogen application rates and yield for 40 sweet and 44 waxy maize varieties in Zhejiang Province, China from 2015 to 2019 across five sites. Nitrogen application rates were categorized as relatively high (RHN: >300 kg ha-1 for sweet maize, >320 kg ha-1 for waxy maize) or relatively low (RLN). An increase in nitrogen application rates for both sweet and waxy maize significantly reduced nitrogen fertilizer partial productivity (R2=0.616, P<0.01; R2=0.643, P<0.01), indicating that the optimum nitrogen application rate in this study might be the lowest values (160 kg ha-1 for sweet maize and 180 kg ha-1 for waxy maize). The kernel number per ear of sweet maize had a potentially more significant impact on fresh grain yield compared to the 1,000-fresh kernel weight both under RLN and RHN. In waxy maize, 1,000-kernel weight contributed more to fresh grain yield under RLN, and kernel number ear-1 and 1,000-kernel weight cooperatively affected yield under RHN. In this study, it was observed that sweet maize required taller plant and ear height, along with an optimal ear-plant height ratio, to enhance dry matter accumulation and increase source size, particularly under RLN, to achieve a higher fresh grain yield. In contrast, a lower ear height and ear-plant height ratio of waxy maize probably contributed more to increased kernel number and weight under RLN, likely due to a lower ear height can reduce the distance between sink and source, enabling more efficient photoassimilate allocation to the ear.

Profiling the selected hotspots for ear traits in two maize-teosinte populations.

Eight selected hotspots related to ear traits were identified from two maize-teosinte populations. Throughout the history of maize cultivation, ear-related traits have been selected. However, little is known about the specific genes involved in shaping these traits from their origins in the wild progenitor, teosinte, to the characteristics observed in modern maize. In this study, five ear traits (kernel row number [KRN], ear length [EL], kernel number per row [KNR], cob diameter [CD], and ear diameter [ED]) were investigated, and eight quantitative trait loci (QTL) hotspots were identified in two maize-teosinte populations. Notably, our findings revealed a significant enrichment of genes showing a selection signature and expressed in the ear in qbdCD1.1, qbdCD5.1, qbpCD2.1, qbdED1.1, qbpEL1.1, qbpEL5.1, qbdKNR1.1, and qbdKNR10.1, suggesting that these eight QTL are selected hotspots involved in shaping the maize ear. By combining the results of the QTL analysis with data from previous genome-wide association study (GWAS) involving two natural panels, we identified eight candidate selected genes related to KRN, KNR, CD, and ED. Among these, considering their expression pattern and sequence variation, Zm00001d025111, encoding a WD40/YVTN protein, was proposed as a positive regulator of KNR. This study presents a framework for understanding the genomic distribution of selected loci crucial in determining ear-related traits.