Leaf Orientation Value Research Articles

Identification of superior genotypes for leaf architecture traits in Sorghum bicolor through GGE biplot analysis

Context Well-organised leaf architecture produces compact canopies and allows for greater sunlight penetration, higher photosynthetic rates, and thus greater yields. Breeding for enhanced leaf architecture of sorghum (Sorghum bicolor L.), a key food source in semi-arid regions, benefits its overall production. Aims The study focuses on selecting useful genotypes with excellent leaf architecture for grain sorghum improvement. Methods In total, 185 sorghum genotypes were subjected to multi-environment trials. Leaf flagging-point length, leaf length, leaf width, leaf angle and leaf orientation value (LOV) were characterised under field conditions. Genotype + genotype × environment interaction (GGE) biplot analysis was used to identify the most stable genotypes with the highest LOV. Key results Statistical analysis showed significant effects of genotype × environment interaction (P < 0.001), and high broad-sense heritability for the traits. Correlation analysis demonstrated negative correlations (P < 0.001) between LOV and its components. Singular value decomposition of LOVs in the first two principal components explained 89.19% of the total variation. GGE biplot analysis identified G55 as the ideotype with the highest and most stable LOV. Conclusions Leaf architecture optimisation should be given greater attention. This study has identified a genotype with optimal and stable leaf architecture, laying the foundation for improvement in breeding to increase overall yields of sorghum. Implications Genotype G55 can be utilised as a parent with other parents that display economically important characteristics in breeding programs to produce offspring that can be planted densely to increase population yields. Genotypes identified with loose leaf architecture are useful in dissecting genes controlling leaf architecture by crossing with G55 to construct genetic mapping populations.

Enhancing maize radiation use efficiency under high planting density by shaping canopy architecture with a plant growth regulator

Optimized maize (Zea mays L.) canopy architecture enhances density-tolerance. DHEAP (N, N-Diethyl-2-hexanoyl oxygen radicals-ethyl amine (2-ethyl chloride) phosphonic acid salt) has been shown to increase maize upper canopy strata compactness, but its overall effect on the whole canopy structure and how it shapes the canopy structure remain unclear. This study examined how DHEAP affected the canopy structure of maize hybrids Zhengdan 958 (ZD958) and Xianyu 335 (XY335), with distinct canopy structures, under different planting densities. The results showed that DHEAP increased the leaf orientation value (LOV) of upper canopy strata by 8.0% while reducing middle and lower strata LOV by 11.7% and 18.4%, respectively. This indicates that DHEAP shaped a canopy structure that was compact in the upper strata and loose in the middle and lower strata. Multiple linear regression analysis showed that leaf angle had a greater impact on the upper canopy strata, while leaf auricle size had a greater impact on the middle and lower canopy strata. After DHEAP treatment, light transmission above different canopy strata increased at the reproductive stage. Concurrently, the middle canopy captured more light energy, enhanced yield formation, and boosted radiation use efficiency by 21.9% under high density. In terms of grain yield, DHEAP treatment resulted in a 9.1% and 23.9% increase in ZD958 and XY335, respectively, under high-density conditions. These results suggest that DHEAP shaped the maize canopy structure with high density tolerance, improved the distribution of light within the canopy, and increased grain yield.

Enhancing maize yield through understanding the novel shoot-root interaction in morphology among hybrids with dense planting

ContextUnderstanding the shoot-root characteristics and their interaction of maize is essential to break the constraints of the densification process and improve grain yield. ObjectiveThe objective of the work was to study the interaction between the above-ground canopy and below-ground root system in morphology and its relationship to grain yield in dense planting with different hybrids. MethodsThis study conducted a 2-yr field experiment with three modern hybrids (JNK728, ZD958 and XY335) at the Wuqiao Experimental Station in Northern China. ResultsAmong hybrids, XY335 attained the highest grain yield of 14,886.9 kg hm−2 in 2019 and 10,078.8 kg hm−2 in 2020 with a density of 7.5 × 104 plants hm−2. For the shoot at the silking stage (R1), the lowest leaf orientation value for both middle and upper leaves and ear-to-height ratio among three hybrids were found in XY335 with the compact plant phenotype. Meanwhile, the highest photosynthesis rate of ear leaves (33.0 umol m2˙s−1) at R1 was also observed in XY335. At physiological maturity (R6), the above-ground dry matter (AGDM) was 4.6%− 10.4% higher in XY335 than the other two hybrids. For the root system at both R1 and R6 with the density of 7.5 × 104 plants hm−2, the highest value for root system indicators in morphology such as root total length (RL), root surface area (RSA), root volume (RV) was observed in XY335. From R1 to R6, RL, RSA and RV in XY335 averaged 24,749.6 cm, 3486.8 cm2, 51.5 cm3, 1.3–14.6% higher than JNK728, and 10.2–23.9% higher than ZD958, respectively. Furthermore, the lower senescence of the root system was also observed in XY335, with a 22.0–32.1% lower decrease from R1 to R6 in RL, RSA, and RV compared with the other two hybrids. ConclusionsFor the shoot-root interaction, per unit decrease in morphology indicator in the root per plant with density increase of XY335 accompanied with more AGDM accumulation and thus higher grain yield. ImplicationsThe observations on shoot-root characteristics and their interaction from this study are essential to selecting a hybrid that allows a better adaptation to planting at high density, developing an effective management strategy, and breeding high-density tolerant hybrids.

Multi-locus genome-wide association studies reveal genetic loci and candidate genes for leaf angle traits in cut chrysanthemum

Chrysanthemum (Chrysanthemum morifolium Ramat.), one of the four most popular cut flowers in the world, occupies a large share of global floriculture trade. Leaf angle (LA) is an important factor affecting plant architecture, photosynthesis and yields of cut chrysanthemum. However, the genetic basis and related genes underlying LA remain largely unknown. In this research, phenotypes of five LA-related traits in 200 cut chrysanthemum accessions were investigated across two consecutive years (Y2020 and Y2021), and their broad-sense genetic heritabilities ranged from 68.91% to 84.70%. Leaf orientation value (LOV) exhibited the maximum phenotypic coefficient of variation of 35.66% in Y2020 and 32.34% in Y2021. A new methodological framework named 3VmrMLM was applied for multi-locus genome-wide association study (GWAS) based on a set of 330,710 single nucleotide polymorphisms (SNPs) to explore the genetic loci and candidate genes of LA. As a result, 303 quantitative trait nucleotides (QTNs) in single-environment, 120 QTNs and 75 QTN × environments interactions (QEIs) in multiple-environments were identified. Among the genes around these QTNs and QEIs, 26 known genes were considered to be associated with LA, including ARF16, IBH1, AN3, etc. Furthermore, the haplotype analysis of ARF16 revealed four accessions with elite LA. Our findings provide a fundamental understanding to the genetic architecture of LA and contribute to further gene cloning and molecular improvement of chrysanthemum plant architecture.

CANOPY ARCHITECTURE AND GRAIN YIELD OF MAIZE (ZEA MAYS L.) IN THE RAINFOREST OF SOUTHWESTERN NIGERIA

Plant architecture is a key factor for optimum productivity in most crops. Unfortunately, this aspect of maize (Zea mays L.) crop configuration has recieved little attention from researchers in the rainforest ecologies of Nigeria.We investigated the effects of the environment on canopy architecture and, in turn, canopy orientation on grain yield of maize in the rainforest of sw Nigeria. Five maize varieties were planted weekly from March to November of 2016 and 2017 in randomized complete block experiments at the Obafemi Awolowo University Teaching & Research Farm (OAU T&RF). Data were collected on canopy architecture, which was quantified with upper and lower leaf angle (LAUpper and LALower) and leaf orientation values (LOVUpper and LOVLower) obtained at the grain-filling stage.-At maturity, grain yield, along with some of its components (ear length, ear diameter and kernel row number) were also obtained from all plots. The data were subjectedto ANOVA, correlation, regression, and sequential path analyses to determine the relationship of grain yield with canopy architecture. The environment and genotype had significant effects on canopy architecture, grain yield (P = 0.01; R2 ≥ 80 %), and yield components. Leaf orientation value of the upper canopy (LOVUpper), with correlation coefficient r = 0.61** and direct positive causal effect (P = 0.61), rather than LAUpper, LALower and LOVLower, greatly affected grain yield. In conclusion, LOVUpper was the single most important leaf architecture index that positively affected grain yield which, in turn, was influenced greatly by the environment in the rainforest ecology of SW Nigeria

Improving the yield potential in maize by constructing the ideal plant type and optimizing the maize canopy structure

AbstractUnderstanding the impact of changes in the crop canopy on yield is important in order to meet future food demands. We designed a field experiment to investigate the relationships between crop‐related factors and yield gaps in maize to enhance crop yields from 2010 to 2018 in Qitai, China. Maize grain yields (n = 247) were divided into four yield ranges: <15 Mg ha−1 (n = 30), 15–18 Mg ha−1 (n = 79), 18–21 Mg ha−1 (n = 114), and >21 Mg ha−1 (n = 24). The characteristics of the maize canopy structure as well as the light interception, photosynthetic potential, and radiation utilization efficiency in these four yield ranges were analyzed. The canopy structure of treated fields with yields >21 Mg ha−1 had a higher leaf area index (7.2), lower ear ratio (0.39), longer internodes above the ear (20.1 cm), larger leaf orientation value (LOV) above the ear (48.6), smaller leaf angle above the ear (18°), and smaller LOV below the ear (36.0) when compared to the other treatments. These findings suggested that the yield gap is dependent on canopy structure, and the evolutionary trend also accounted for significant increases in post‐LAD (p < 0.01), changes in crop growth rate (CGR; p < 0.01), net assimilation rate (NAR; p < 0.05), and radiation utilization efficiency. The radiation utilization efficiencies in the 15–18, 18–21, and >21 Mg ha−1 treatments (1.23, 1.28, and 1.38 g MJ−1, respectively) were higher than for the <15 Mg ha−1 treatment (1.10 g MJ−1). Furthermore, there are opportunities to narrow the yield gaps by optimizing the canopy structure to make full use of the solar radiation resources. Our results will help breeders choose an ideal canopy structure to improve yield. In addition, our results may serve as a general guide for other maize growing regions.

Maize transcription factor ZmNF-YC13 regulates plant architecture.

Leaf angle and leaf orientation value (LOV) are critical agronomic traits for maize plant architecture. The functions of NUCLEAR FACTOR Y (NF-Y) members in regulating plant architecture have not been reported yet. Here, we identified a regulator of maize plant architecture, NF-Y subunit C13 (ZmNF-YC13). ZmNF-YC13 was highly expressed in the leaf base zone of maize plants. ZmNF-YC13 overexpressing plants showed upright leaves with narrow leaf angle and larger LOV, while ZmNF-YC13 knockout plants had larger leaf angle and smaller LOV compared with wild-type plants. The changes in plant architecture were due to the changes in the expression of cytochrome P450 family members. ZmNF-YC13 interacts with two NF-Y subunit B members (ZmNF-YB9 and ZmNF-YB10) of the LEAFY COTYLEDON1 sub-family, and further recruits NF-Y subunit A (ZmNF-YA3) to form two NF-Y complexes. The two complexes can both activate the promoters of transcriptional repressors (ZmWRKY76 and ZmBT2), and the promoters of PLASTOCHRON group genes can be repressed by ZmWRKY76 and ZmBT2 in maize protoplasts. We propose that ZmNF-YC13 functions as a transcriptional regulator and, together with ZmNF-YBs and ZmNF-YA3, affects plant architecture by regulating the expression of ZmWRKY76 and ZmBT2, which repress the expression of cytochrome P450 family members in PLASTOCHRON branch.

Identification and meta-analysis of QTLs for four leaf shape traits in two maize populations under contracting watering environments

Maize leaf length, leaf width, leaf angle, and leaf orientation value are determinant traits influencing leaf shape, yield potential, and can sense water stress signals. However, little is known regarding their genetic controls under drought stress. Using two F3 populations, we identified 72 QTLs under contrasting environments at V18 and R1 stages by single-environment mapping, 58.3% QTLs were identified under drought-stressed environments. Thirty-three joint QTLs were detected by joint analysis of all environments, 7 QTLs involved in QTL-by-environment interactions, 11 pair epistasis exhibited additive-by-additive effects. Twelve constitutive QTLs were dissected that will be potentially useful for genetic improvement of maize leaf development through QTL pyramiding. Additionally, 13 meta-QTLs were identified via meta-analysis, 15 candidate genes were identified in these meta-QTLs. These results provide valuable information for QTLs fine mapping, revealing genetic mechanisms of leaf shape under contrasting watering environments, and alleles provide useful targets for marker-assisted selection breeding.

Identification of QTLs and Candidate Genes Associated with Leaf Angle and Leaf Orientation Value in Maize (Zea mays L.) Based on GBS

Leaf angle (LA) and leaf orientation value (LOV) are two crucial traits constituting the plant architecture (PA) of maize. Screening of quantitative trait loci (QTLs) and candidate genes (CGs) related to leaf angle and leaf orientation value provides the molecular basis for the improvement of maize plant architecture. In this study, we utilized genotyping by sequencing (GBS) on 179 maize recombined inbred lines (RILs) obtained by crossing two inbred lines with significant variation in leaf angle and leaf orientation value. A total of 4235 markers were used for the construction of the genetic linkage map. The total length of the genetic map was 1514.57 cM with the average genetic distance between each marker of 0.36 cM. On association of this map with phenotypic data from four environments, nine QTLs associated with leaf angle and nine QTLs associated with leaf orientation value were identified, explaining 78.89% and 59.71% of the phenotypic variation of leaf angle and leaf orientation value, respectively. Two QTLs explained greater than 10% of the phenotypic variation and three QTLs controlling both leaf angle and leaf orientation value were screened. Three candidate genes were identified as the most possible genes associated with leaf angle and leaf orientation value by screening the annotations of genes underlying these crucial QTLs. These were Zm00001d019053 might be associated with leaf angle, Zm00001d028164 and Zm00001d025352 might be associated with leaf angle and leaf orientation value, respectively. Expression analysis of candidate genes from parents and subsets also confirmed the significant variation in expression. Differences in DNA of the inbred lines with different phenotype were identified based on analysis of allelic variations in the candidate genes. These results not only enrich QTLs and candidate genes associated with leaf angle and leaf orientation value of maize, but also provide references for the improvement of plant architecture and molecular marker-assisted breeding.

Genome-wide association studies of leaf orientation value in maize

<p indent=0mm>Leaf orientation value is a comprehensive index reflecting the two characteristics of “straight” and “vertical” of leaves. The varieties with high leaf orientation value have straight and not curved leaves, and small angle, which are conducive to the wind ventilation and light transmission for maize population. When the planting density is high, it is easier to obtain high yield than the expanded plant-type. It is of great significance for molecular design breeding of ideal plant type to clarify the genetic basis of leaf orientation value. In this study, 285 diverse lines genotyped by the MaizeSNP50 chip were evaluated for leaf orientation in 2017 and 2018. The genome-wide association analysis (GWAS) were used to identified the SNPs, which were significant association with leaf orientation values. The analysis of variance showed that the significant variations were observed for leaf orientation value of different inbred lines (<italic>P</italic> < 0.01). In the selection of the optimal model, it was found that the Q + K model was the most suitable for the leaf orientation association analysis in this study. A total of 15 loci (<italic>P</italic> < 4.05E-5) were detected by GWAS, including 27 SNPs, explaining 5.54%–8.73% of phenotypic variation, and 15 candidate genes were mined in two years. Among them, site 2 in 1.07 bin was an important site found in this study, and its candidate gene might be <italic>Zm00001d032050</italic> encoding cyclin dependent protein kinase, which needed to be further confirmed by map-based cloning.

Genetic control of maize plant architecture traits under contrasting plant densities

Plant architecture has played an important role in the adaptation of maize (Zea mays L.) hybrids to historical increases in plant density in order to maximize yields per unit area. At high density, a compact plant structure would allow for less interference by light among plants of the row and a deeper penetration of the radiation towards the lowest canopy layers, without compromising the capture of radiation at crop level. The genetic control of plant architecture traits of maize under contrasting plant densities remains poorly understood. In this work, traits related to leaf and stem architecture were phenotypically analyzed and QTLs were mapped using 160 RILs from the IBM B73 × Mo17 Syn4 population cultivated at low density and high density during 2013–2014 and 2014–2015 growing seasons in Buenos Aires province, Argentina. Forty-nine QTLs were detected on chromosomes 1, 3, 4, 5, 9 and 10. Most QTLs of vertical insertion angle of leaves and leaf orientation value (i.e., vertical angle affected by the curvature of leaves) were detected on chromosome 5 at high density and showed a high percentage of co-location. Detected QTLs for plant and ear height, and the relationship between them were concentrated on chromosome 9, with consistent effect under different density × environment combinations. These regions had large-effect QTLs and constitute hot spots that need to be studied in more detail to determine their potential use in breeding programs.

Genetic mapping of quantitative trait locus for the leaf morphological traits in a recombinant inbred line population by ultra‐high–density maps across multi‐environments of maize (Zea mays)

AbstractLeaf is the main organ of photosynthetic reaction of plants. Studying the genetic mechanism that affects the leaf shape is very important for the improvement of maize production. In this study, a RIL population, derived from a cross between Ye478 and Qi319, was planted in four different environments, and six leaf morphological traits were measured, including the leaf angle of first leaf above ear, the leaf angle of first leaf below ear, leaf orientation value, leaf area of first leaf above ear, leaf area of ear and leaf area of first leaf below ear. By combining with a genetic map containing 4,602 bin markers, 39 QTLs associated with leaf morphological traits were identified. Among them, four QTLs explained more than 10% of the phenotypic variance, and the QTL qLOV8‐2 which controlled LOV not only had a phenotypic contribution rate of 13.86% but also was detected in four environments, which could be considered as a stable major QTL. These results provide useful information for understanding the molecular mechanisms controlling maize leaf morphological traits.

Exploiting genotype x environment x management interactions to enhance maize productivity in Ethiopia

Maize is the main staple food crop grown by smallholder farmers in Ethiopia. High variability in inter-seasonal rainfall presents the biggest risk for farmers to invest in best management practices in maize crop grown in Ethiopia. Optimising genotype (G) and management (M) of maize for different growing environments (E) could alleviate risks associated with seasonal rainfall variability and enhance reliability of yield of this crop. The objectives of this study were to quantify G x E x M interactions and identify best combinations of G and M for target maize production environments in Ethiopia. Ten genotypes, five each from early and medium maturity classes were evaluated at five planting densities, 2, 5, 6, 7 and 9 plants m−2, across seven environments in 2013 and 2014 cropping seasons. Our study explored a range of morphological, phenological and physiological traits underpinning the yield of maize. Our results revealed that combining the appropriate G and M is more effective than relying on the choice of genotypes. The optimum plant densities identified in this study are higher than the plant densities currently used by farmers. Planting BH-546 and TH13321 at 7 plants m−2 substantially increased yield compared with other genotypes. For instance, yield for TH13321 was higher by 48% (3.7 t ha-1) at 7 plants m−2 in high yielding environments compared with BH-540, the most widely grown hybrid by farmers. This indicates the need for optimising G and M and using versatile genotypes to exploit variability in weather and input-use in the country. The genotypes substantially varied for their response to radiation use efficiency, rainwater productivity and leaf orientation value at high plant density. The least response to these traits observed for BH-540 highlights the need for a reassessment of current varietal and agronomic options for maize production in Ethiopia. Information from this study could be extended to sub-Saharan African countries that are similarly using low plant density.

Screening and verification of genes associated with leaf angle and leaf orientation value in inbred maize lines.

Leaf angle and leaf orientation value are important traits affecting planting density and photosynthetic efficiency. To identify the genes involved in controlling leaf angle and leaf orientation value, we utilized 1.49×106 single nucleotide polymorphism (SNP) markers obtained after sequencing 80 backbone inbred maize lines in Jilin Province, based on phenotype data from two years, and analyzed these two traits in a genome-wide association study (GWAS). A total of 33 SNPs were significantly associated (P<0.000001) with the two target traits. Twenty-two SNPs were significantly associated with leaf angle and distributed on chromosomes 1, 3, 4, 5, 6, 7, 8, and 9, explaining 21.62% of the phenotypic variation. Eleven SNPs were significantly associated with leaf orientation value and distributed on chromosomes 1, 3, 4, 5, 6, 7, and 9, explaining 29.63% of the phenotypic variation. Within the mean linkage disequilibrium (LD) distance of 9.7 kb for the significant SNP locus, 22 leaf angle candidate genes were detected, and 3 of these candidate genes harbored significant SNPs, with phenotype contribution rates greater than 10%. Two candidate genes at distances less than 100 bp from significant SNPs showed phenotype contribution rates greater than 8%. Seven leaf orientation value candidate genes were detected: 3 of these candidate genes harbored significant SNPs, with phenotype contribution rates greater than 10%. Eight inbred maize lines with significant differences in leaf angle and leaf orientation value were selected to test candidate gene expression levels from 182 recombinant inbred lines (RILs). The 5 leaf angle candidate genes and 3 leaf orientation value candidate genes were verified using quantitative real-time PCR (qRT-PCR). The results showed significant differences in the expression levels of the above eight genes between inbred maize lines with significant differences in leaf angle and leaf orientation value.

QTL mapping for six ear leaf architecture traits under water‐stressed and well‐watered conditions in maize (Zea mays L.)

AbstractMorphological traits for ear leaf are determinant traits influencing plant architecture and drought tolerance in maize. However, the genetic controls of ear leaf architecture traits remain poorly understood under drought stress. Here, we identified 100 quantitative trait loci (QTLs) for leaf angle, leaf orientation value, leaf length, leaf width, leaf size and leaf shape value of ear leaf across four populations under drought‐stressed and unstressed conditions, which explained 0.71%–20.62% of phenotypic variation in single watering condition. Forty‐five of the 100 QTLs were identified under water‐stressed conditions, and 29 stable QTLs (sQTLs) were identified under water‐stressed conditions, which could be useful for the genetic improvement of maize drought tolerance via QTL pyramiding. We further integrated 27 independent QTL studies in a meta‐analysis to identify 21 meta‐QTLs (mQTLs). Then, 24 candidate genes controlling leaf architecture traits coincided with 20 corresponding mQTLs. Thus, new/valuable information on quantitative traits has shed some light on the molecular mechanisms responsible for leaf architecture traits affected by watering conditions. Furthermore, alleles for leaf architecture traits provide useful targets for marker‐assisted selection to generate high‐yielding maize varieties.

Morphological Variation of Maize Cultivars in Response to Elevated Plant Densities

Core Ideas Maize can adjust its morphology to adapt to the low light environment in close planted stands. Maize adapts to close planting by increasing leaf spacing below the ear and leaf orientation value above the ear, and by reducing leaf width and leaf angle. Morphological changes allow more light transmission into the mid‐ and lower canopy under high plant density. Increasing plant density is a common method for increasing maize (Zea mays L.) yield. However, the yield increases are limited by light competition and mutual shading that occur within close canopies. The objectives of this 2‐yr field experiments were to determine the effect of plant density on maize plant morphology, canopy structure, and canopy light distribution. The leaf length, leaf width, leaf area and leaf area index (LAI) increased from both the top and the bottom of the canopy. The leaf angle generally decreased from the bottom to top of the canopy; however, the leaf orientation value (LOV) displayed the opposite trend. The leaf length and width decreased as plant density increased. The decrease in width was greater than in length. Changes in leaf dimensions caused leaf area to decline. Increasing plant density resulted in a decrease in leaf angle; however, an increase in LOV. Changes in the leaf canopy were more affected above the ear compared to below the ear as plant density increased. This made the leaves above the ear more upright as plant density increased. The leaf spacing below the ear increased as the plant increased, causing the ear height, plant height coefficient to increase. Light intensity within maize canopy decreased with increasing density. The results indicate that maize adapts to increasing density by (i) increasing leaf spacing below the ear and LOV above the ear and by (ii) reducing leaf width and leaf angle. These changes allow more light transmission into the mid‐ and lower canopy.

Detection of epistatic and environmental interaction QTLs for leaf orientation‐related traits in maize

AbstractLeaf architecture traits in maize are quantitative and have been studied by quantitative trait loci (QTLs) mapping. However, additional QTLs for these traits require mapping and the interactions between mapped QTLs require studying because of the complicated genetic nature of these traits. To detect common QTLs and to find new ones, we investigated the maize traits of leaf angle, leaf flagging‐point length, leaf length and leaf orientation value using a set of recombinant inbred line populations and single nucleotide polymorphism markers. In total, 19 QTLs contributed 4.13–13.52% of the phenotypic effects to the corresponding traits that were mapped, and their candidate genes are provided. Common and major QTLs have also been detected. All of the QTLs showed significant additive effects and non‐significant additive × environment effects in combined environments. The majority showed additive × additive epistasis effects and non‐significant QTL × environment effects under single environments. Common and major QTLs provided information for fine mapping and gene cloning, and SNP markers can be used for marker‐assisted selection breeding.

Genetic control of the leaf angle and leaf orientation value as revealed by ultra-high density maps in three connected maize populations.

Plant architecture is a key factor for high productivity maize because ideal plant architecture with an erect leaf angle and optimum leaf orientation value allow for more efficient light capture during photosynthesis and better wind circulation under dense planting conditions. To extend our understanding of the genetic mechanisms involved in leaf-related traits, three connected recombination inbred line (RIL) populations including 538 RILs were genotyped by genotyping-by-sequencing (GBS) method and phenotyped for the leaf angle and related traits in six environments. We conducted single population quantitative trait locus (QTL) mapping and joint linkage analysis based on high-density recombination bin maps constructed from GBS genotype data. A total of 45 QTLs with phenotypic effects ranging from 1.2% to 29.2% were detected for four leaf architecture traits by using joint linkage mapping across the three populations. All the QTLs identified for each trait could explain approximately 60% of the phenotypic variance. Four QTLs were located on small genomic regions where candidate genes were found. Genomic predictions from a genomic best linear unbiased prediction (GBLUP) model explained 45±9% to 68±8% of the variation in the remaining RILs for the four traits. These results extend our understanding of the genetics of leaf traits and can be used in genomic prediction to accelerate plant architecture improvement.

Changes in the morphological traits of maize genotypes in China between the 1950s and 2000s

Maize (Zea mays L.) morphological traits influence light attenuation within the canopy, and, ultimately, yield. The objectives of this 3-year field study were to: (i) examine the morphological characteristics of specific genotypes using varieties of maize that were widely used in Chinese agriculture from the 1950s to the 2000s; (ii) assess the canopies and yields of maize populations in relation to changes in their morphological characteristics. There were significant decrease on the ear ratio, center of gravity height and leaf angle with improved genotypes regardless of plant density. However, the ear leaves and adjacent leaves appeared to be longer in improved maize varieties. The mean leaf orientation value (LOV) and individual LOVs increased considerably during the time series of the genotypes, but more obvious changes in LOV occurred in the uppermost leaves. The average leaf area (LA) per plant and LA on the ears increased significantly from the 1950s to the 2000s. At the optimum density, current hybrid's canopy architecture was more compact, having short plant height and more upright leaf. The SDLA above or under ear significantly increased with improving genotypes, mainly due to new hybrids allowing the use of more individuals per area and thus increasing leaf area index (LAI). At the highest plant density, new hybrids had the rates of light transmittance (0.04–0.05), low attenuation coefficient (K=0.47) and gained the highest yield. Leaf angle and LOV were highly correlated with TPAR/IPAR on ear, K, grain yield. Consequently, yield improvement in maize was probably a result of increased plant density tolerance through dependence on changes in leaf orientation characteristics.

Integrated multiple population analysis of leaf architecture traits in maize (Zea mays L.)

Leaf morphology in maize is regulated by developmental patterning along three axes: proximodistal, mediolateral, and adaxial-abaxial. Maize contains homologues of many genes identified as regulators of leaf development in other species, but their relationship to the natural variation of leaf shape remains unknown. In this study, quantitative trait loci (QTLs) for leaf angle, leaf orientation value, leaf length, and leaf width were mapped by a total of 256 F(2:3) families evaluated in three environments. Meta-analysis was used to integrate genetic maps and detect QTLs across several independent QTL studies, on the basis of the previously reported experimental results for leaf architecture traits. Candidate gene sequences for leaf architecture were mapped in the integrated consensus genetic map. In total, 21 QTLs and 17 meta-QTLs (mQTLs) were detected. Among these QTLs, qLA1-1 and qLA2 were consistently detected in five and three populations respectively, and six of seven QTLs with contributions (R(2)) >10% were integrated in mQTLs. Six key mQTLs (mQTL1-1, mQTL2-1, mQTL3-3, mQTL5-1, mQTL7-2, and mQTL8-1) with R(2) of some initial QTLs >10% included 4-6 initial QTLs associated with 2-4 traits. Therefore, the chromosome regions for six mQTLs with high QTL co-localization might be hot spots of the important QTLs for the associated traits. Fifteen key candidate genes controlling leaf architecture traits coincided with 11 corresponding mQTLs, namely DWARF4, KAN3, liguleless1, TAC1, ROT3, AS2/liguleless2, PFL2, yabby9/SE/LIC/yabby15, mwp1, CYCD3;2, and CYCB1. In particular, DWARF4, liguleless1, AS2/liguleless2, yabby9/SE/LIC/yabby15, and CYCD3;2 were mapped within the important mQTL1-1, mQTL2-1, mQTL3-3, mQTL5-1, and mQTL7-2 intervals, respectively. Fine mapping or construction of single chromosome segment lines for genetic regions of these five mQTLs is worth further study and could be put to use in marker-assisted breeding. In conclusion, the results provide useful information for further research and help to reveal the molecular mechanisms with regard to leaf architecture traits.