Kernel Thickness Research Articles

Genome‑wide identification and expression analysis of the UBC gene family in wheat (Triticum aestivum L.)

BackgroundUbiquitination is an important regulatory step of selective protein degradation in the plant UPS (ubiquitin–proteasome system), which is involved in various biological processes in eukaryotes. Ubiquitin-conjugating enzymes play an intermediate role in the process of protein ubiquitination reactions and thus play an essential role in regulating plant growth and response to adverse environmental conditions. However, a genome-wide analysis of the UBC gene family in wheat (Triticum aestivum L.) has not yet been performed.ResultsIn this study, the number, physiochemical properties, gene structure, collinearity, and phylogenetic relationships of TaUBC family members in wheat were analyzed using bioinformatics methods. The expression pattern of TaUBC genes in different tissues/organs and developmental periods, as well as the transcript levels under abiotic stress treatment, were analyzed using RNA-Seq data and qRT-PCR. Meanwhile, favorable haplotypes of TaUBC25 were investigated based on wheat resequencing data of 681 wheat cultivars from the Wheat Union Database. The analyses identified a total of 93 TaUBC family members containing a UBC domain in wheat genome. These genes were unevenly distributed across 21 chromosomes, and numerous duplication events were observed between gene members. Based on phylogenetic analysis, the TaUBC family was divided into 13 E2 groups and a separate UEV group. We investigated the expression of TaUBC family genes under different tissue/organ and stress conditions by quantitative real-time PCR (qRT-PCR) analysis. The results showed that some TaUBC genes were specifically expressed in certain tissues/organs and that most TaUBC genes responded to NaCl, PEG6000, and ABA treatment with different levels of expression. In addition, we performed association analysis for the two haplotypes based on key agronomic traits such as thousand-kernel weight (TKW), kernel length (KL), kernel weight (KW), and kernel thickness (KT), examining 122 wheat accessions at three environmental sites. The results showed that TaUBC25-Hap II had significantly higher TKW, KL, KW, and KT than TaUBC25-Hap I. The distribution analysis of haplotypes showed that TaUBC25-Hap II was preferred in the natural population of wheat.ConclusionOur results identified 93 members of the TaUBC family in wheat, and several genes involved in grain development and abiotic stress response. Based on the SNPs detected in the TaUBC sequence, two haplotypes, TaUBC25-Hap I and TaUBC25-Hap II, were identified among wheat cultivars, and their potential value for wheat breeding was validated by association analysis. The above results provide a theoretical basis for elucidating the evolutionary relationships of the TaUBC gene family and lay the foundation for studying the functions of family members in the future.

Breakage behavior of corn kernels subjected to repeated loadings

Studying the breakage behavior of corn kernels subjected to repeated compressive events, including at low frequency and low strain rate, are important for the development of breakage models for prediction of kernel breakage in handling and processing machines. The main purpose of this study was to identify the breakage behavior and mechanism of weakening of corn kernels under repeated loadings as affected by their moisture content and kernel thickness. Corn kernels at four moisture content levels (8.20%, 11.95%, 16.00%, 20.02%) and in four thickness ranges were subjected to repeated compressive loading between two parallel steel plates in quasi-static regime at a constant loading rate of 2 mm/min (strain rates from 4.7 × 10−3 to 1.0 × 10−2). Conducted experiments allow to observe the different grain breakage patterns, identify the crack initiation and its development, describe the weakening of kernels by changes in the total specific energy, plastic and elastic deformation energies, and the number of loading cycles to break (breakage probability) the kernels. The results indicate that the breakage models describing the damage and weakening of grains in terms of changes in the total and strain energy or changes in the stiffness can be used for understanding the effect of moisture content and thickness on breakage of corn kernels.

Impact of Kernel Thickness on Germination and Vigor of Seed Rice

Highlights The impact of kernel thickness grading on seed germination and vigor was explored in medium and low moisture content seeds using two hybrid rice cultivars (RTv7303 & RT7301). Rough rice samples were size fractionated into two thickness fractions (thick >2.03 mm and thin 1.91>>2.03 mm) and dried to 12.5% moisture content (MC) at temperatures of 40°C and 60°C and 25% relative humidity (RH). It was discovered that harvested rice seeds at a medium MC (19% to 21%) and a temperature of 60°C increased seed germination and vigor. Thick kernels outperformed thin kernels in terms of seed germination but were not statistically different when compared to unsorted kernels. ABSTRACT. Rough rice lots harvested on the field contain varying kernel thicknesses within the panicles. These variations influence the drying characteristics of seeds and, thus, the seed germination and vigor. In this study, two hybrid long-grain rice cultivars (RTv 7303 & RT 7301) with harvest moisture contents (HMC) ranging from 19% to 21% and 15% to 17% wet basis (w.b.) for medium and low MC seeds were used, respectively. These rough rice samples were size fractionated into two thickness fractions (thick >2.03 mm and thin 1.91>>2.03 mm), with non-fractionated samples labeled as unsorted or control samples. Kernels from each sub-lot were dried to 12.5% MC at 40°C and 60°C air temperatures and 25% constant relative humidity (RH). Immediately after drying, samples were selected for seed germination and vigor assessments. RTv 7303 had higher seed germination compared to RT 7301, indicating that the two cultivars were genetically different from each other. Thick kernels had significantly higher seed germination (SG) than thin kernels, but there was no significant difference compared to unsorted kernels. Additionally, the percentage points difference between the thick versus unsorted and thin kernels varies from ˜1-pp to 8-pp for low MC seeds and from 2.5-pp to 6-pp for medium MC seeds. The seed vigor index (SVI) difference between the two cultivars is around 3.0 m.% and 1.5 m.% for medium and low MC, respectively. Harvested rice seeds with a medium MC (19% to 21%) and dried at a temperature of 60°C resulted in greater seed germination and vigor. Ultimately, these findings highlight the role of thickness grading in seed assessments. Thus, it was concluded that if the thin kernels could be screened out from the harvested rice lots, seed germination and vigor would increase significantly. Keywords: Rice drying, Rice seed, Seed germination, Seed vigor, Thickness grading.

Hotspot Regions of Quantitative Trait Loci and Candidate Genes for Ear-Related Traits in Maize: A Literature Review.

In this study, hotspot regions, QTL clusters, and candidate genes for eight ear-related traits of maize (ear length, ear diameter, kernel row number, kernel number per row, kernel length, kernel width, kernel thickness, and 100-kernel weight) were summarized and analyzed over the past three decades. This review aims to (1) comprehensively summarize and analyze previous studies on QTLs associated with these eight ear-related traits and identify hotspot bin regions located on maize chromosomes and key candidate genes associated with the ear-related traits and (2) compile major and stable QTLs and QTL clusters from various mapping populations and mapping methods and techniques providing valuable insights for fine mapping, gene cloning, and breeding for high-yield and high-quality maize. Previous research has demonstrated that QTLs for ear-related traits are distributed across all ten chromosomes in maize, and the phenotypic variation explained by a single QTL ranged from 0.40% to 36.76%. In total, 23 QTL hotspot bins for ear-related traits were identified across all ten chromosomes. The most prominent hotspot region is bin 4.08 on chromosome 4 with 15 QTLs related to eight ear-related traits. Additionally, this study identified 48 candidate genes associated with ear-related traits. Out of these, five have been cloned and validated, while twenty-eight candidate genes located in the QTL hotspots were defined by this study. This review offers a deeper understanding of the advancements in QTL mapping and the identification of key candidates associated with eight ear-related traits. These insights will undoubtedly assist maize breeders in formulating strategies to develop higher-yield maize varieties, contributing to global food security.

Morphological characterization of wild Prunus scoparia Spach accessions in 11 provinces of Iran

Prunus scoparia (Spach) C. K. Schneid is among the most prevalent species which has the potential of being used as a dwarf rootstock for the cultivated almond. In the present study, the phenotypic variation of 521 wild accessions of this species naturally grown in 29 areas of 11 provinces in Iran was assessed. The accessions investigated showed significant differences based on the measured traits. The majority of the characters measured (90 out of 100) exhibited a coefficient of variation of higher than 20.00%, indicating considerable variation among the accessions. The range of nut-related characters was as follows: nut length: 9.72–22.87 mm, nut width: 5.81–15.54 mm, nut thickness: 5.67–12 mm, and nut weight: 0.18–0.99 mm. The range of kernel-related characters was as follows: kernel length: 6.83–19.23 mm, kernel width: 4.28–10.32 mm, kernel thickness: 2.16–7.52 mm, and kernel weight: 0.03–0.37 g. Kernel weight exhibited positive and significant correlations with nut length (r = 0.57), nut width (r = 0.54), nut thickness (r = 0.42), nut weight (r = 0.69), kernel length (r = 0.75), kernel width (r = 0.78), and kernel thickness (r = 0.58). Cluster analysis based on Ward’s method showed two different major clusters among all the accessions. Based on the bi-plot created using principal component analysis of population analysis, the studied 29 natural habitats formed four groups. The studied accessions showed considerable variation in terms of the measured traits within and among populations. This variation is due to cross-pollination, cross-incompatibility, natural hybridization, propagation by seeds, gene flow, and exchange of plant material between the study areas. By using crosses between accessions of different regions, it is possible to increase the amount of variability in different traits of wild almonds.

Study on compositional changes of king coconut (<em style="mso-bidi-font-style: normal;">Cocos nucifera </em>var. aurantiaca) water and kernel during maturation  and evaluation of optimum quality characteristics targeting commercial applications

King coconut (Cocos nucifera var. aurantiaca) is a tropical nut with notable nutritional and medicinal values. King coconut water (KCW) and king coconut kernel (KCK) are sweet and refreshing. They undergo several changes during maturation. The objective of this study was to assess the physico-chemical changes of KCW and KCK with maturity. Three different maturity stages (6, 7, and 8 months) of the variety aurantica, known locally as ‘Nawasi Thembili’ were studied for several physico-chemical parameters. Whole nut weight (g), nut-circumference (cm), colour (water/kernel) (*L), nut-water volume (mL), kernel weight (g), and kernel thickness (mm) were assessed as physical parameters, while pH, total soluble solids (oBrix), titratable acidity (as % ascorbic acid), total sugars (g/100g; g/100mL), and minerals (mg/L; mg/kg) were analysed as chemical attributes. Sugars were estimated using Agilent 1260 HPLC and ICP-MS was used to measure the mineral profile. Results revealed that all the tested physical parameters of KCW and KCK increased significantly (p < 0.05) with maturity. The pH, TSS, total sugars, and acidity of KCW increased significantly (p < 0.05), while mineral content decreased significantly (p < 0.05) with maturity. However, the TSS and minerals of KCK decreased significantly (p < 0.05) with maturity and a higher sucrose content was reported in KCK compared to KCW at later maturity. The Ca+2 and Mg+2 were prominent in both KCW and KCK. The study concluded that the physico-chemical characteristics varied widely with the maturity of king coconuts. The selection of optimum harvest maturity to match the preferred attributes of intended applications is suggested.

Morphological characterization of maize genotypes in Sylhet

Maize plays an important role both as food and feed throughout the world. For morphological characterization and evaluation of yield attributes of maize genotypes an experiment was carried out at the experimental field of the Department of Crop Botany and Tea Production Technology, Sylhet Agricultural University (SAU). The experimental materials were seven exotic maize genotypes viz.ZM 0001, ZM 0002, ZM 0003, ZM 0004, ZM 0005, ZM 0006ZM 0007 along with BARI Maize 6 as control. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. Significant variations were observed among eight maize genotypes for most of the plant characters studied. The tallest plant was found in ZM 0005(246.5 cm). The highest number of leaves was produced in ZM 0001 (14.01). The longest and widest leaf was recorded in ZM 0004 (94.67 cm) and BARI Maize 6 (10.32 cm), respectively. The longest internode was found in ZM 0004 and ZM 0005 (21.61 cm). The genotype ZM 0004 was the earliest in respect of tasseling and silking. Ear height was highest in ZM 0005 (143.8 cm). The genotype ZM 0004 matured the earliest (109.3 days) while BARI Maize 6 matured the last (126 days). No variation was found for ear shape but in terms of kernel color, kernel type, kernel row arrangement and shape of upper surface of the kernel there were great variations among the genotypes. BARI Maize 6 produced the largest kernel with the highest thousand kernel weight. Grain yield plant-1 t ha-1 was highest in BARI Maize 6 which was closely followed by ZM 0005 and ZM 0004 among the studied genotypes. A correlation study between the yield and yield contributing characters showed that ear length, ear diameter, number of kernels row-1, kernel length, kernel width, kernel thickness, thousand kernel weights, and the weight of kernels ear-1, prolificacy index and weight of kernels plant-1 had a significant positive correlation with grain yield. Vol. 10, No. 1, April 2023: 21-32

Selection of superior late-blooming almond (Prunus dulcis [Mill.] D.A.Webb) genotypes using morphological characterizations.

Almond (Prunus dulcis [Mill.] D.A.Webb) is one of the earliest domesticated trees and the evidence dates back to 3000-2000 BC. In the present study, 198 almond seedling origin trees were studied to select late-flowering genotypes having high kernel quality. Significant variabilities were exhibited among the genotypes investigated based on the recorded traits. Full-blooming date ranged from mid-March to mid-April. The Ward dendrogram clustered the genotypes into two major clusters forming several subclusters. After clustering the genotypes based on the full-blooming dates, 68 late-blooming genotypes were recognized and reanalyzed based on the quantitative characters to select the superior ones. Nut-related characters were as follows: nut length: 22.34-43.05 mm, nut width: 14.07-24.34 mm, nut thickness: 9.21-18.00 mm, nut weight: 1.88-6.62 g, and shell thickness: 2.26-4.59 mm. Kernel-related characters were as follows: kernel length: 16.73-25.91 mm, kernel width: 8.50-13.64 mm, kernel thickness: 3.56-7.37 mm, and kernel weight: 0.35-1.41 g. Kernel weight was positively and significantly associated with nut weight, kernel thickness, kernel length, kernel width, nut length, and branch leaf width. Thus, these key variables are the main traits accounting for kernel weight, and they should be considered together in breeding with aiming at increasing the kernel weight. Based on ideal values of the important and commercial characters of almond, such as fruit yield, nut weight, shell hardness, kernel shape, kernel weight, and kernel taste, 19 late-blooming genotypes were promising and are recommended for cultivation in orchards.

The intensity of the cluster drop affects the bioactive compounds and fatty acid composition in hazelnuts

This study was conducted to determine how the intensity of the cluster drop effects nut traits, bioactive compounds, and fatty acid composition in Tombul, Palaz and Kalınkara hazelnut cultivars. The cluster drop significantly affected bioactive compounds and fatty acid composition while it did not affect the traits of the nuts. As cluster drop intensity increased, nut traits and bioactive compounds in all cultivars increased. Strong cluster drop intensity determined the highest total phenolics, total flavonoids, and antioxidant activity. Except for the Kalınkara cultivar, a low amount of linoleic acid was detected while high amounts of oleic and stearic acid were determined in slight cluster drop intensity. As cluster drop intensity increased, palmitic acid increased. Principal component analysis showed that the slight and intermediate drop intensity were generally associated with kernel length, oleic, linoleic, stearic, palmitoleic, 11-eicosenoic and arachidic acids. In contrast, strong intensity was associated with nut and kernel weight, kernel ratio, kernel width, kernel thickness, kernel size, bioactive compounds, and palmitic acid. As a result, the bioactive compounds and fatty acid composition, which are important for human health, was significantly affected by cluster drop intensity.

An analysis of the correlations between the hardness index and selected physicochemical properties of wheat grain

The processes of grain grinding and milling are affected by the physical properties of kernels, whereas energy consumption during these processes is influenced mainly by their mechanical properties. Therefore, the main aim of this study was to determine the relationships between selected physicochemical properties of wheat grain classified into different hardness groups. Technological (processing), mechanical and geometric properties of grain were evaluated in 12 wheat cultivars produced in Poland. The cultivars were divided into four grain hardness groups. The results were analyzed using the following statistical modules: descriptive statistics, one-way analysis of variance (ANOVA), correlation analysis, and regression analysis. Kernels of various hardness were found in each of the evaluated wheat cultivars, in particular those classified as medium soft and medium hard. The type and strength of correlations between the analyzed properties of grain were considerably affected by kernel hardness. The greatest differences were observed in comparisons of the following pairs of kernel parameters: length and width, length and relative strain, length and rupture force, and rupture force and relative strain. On average, the strongest correlations were noted between rupture force and rupture energy, and between kernel thickness and mass, whereas the weakest correlation was found between kernel mass and relative strain. The study demonstrated that the mechanical properties of wheat grain were not affected by crude protein content or total ash content. Grain hardness was correlated with kernel length, vitreousness, rupture force, and rupture energy. The hardness index (HI) increased by 110% within the range of average kernel length values (from approx. 5.4 mm to approx. 8.0 mm). The increase in HI values was accompanied by an increase in rupture force (by approx. 90%) and rupture energy (by approx.115%).

A Systemic Investigation of Genetic Architecture and Gene Resources Controlling Kernel Size-Related Traits in Maize.

Grain yield is the most critical and complex quantitative trait in maize. Kernel length (KL), kernel width (KW), kernel thickness (KT) and hundred-kernel weight (HKW) associated with kernel size are essential components of yield-related traits in maize. With the extensive use of quantitative trait locus (QTL) mapping and genome-wide association study (GWAS) analyses, thousands of QTLs and quantitative trait nucleotides (QTNs) have been discovered for controlling these traits. However, only some of them have been cloned and successfully utilized in breeding programs. In this study, we exhaustively collected reported genes, QTLs and QTNs associated with the four traits, performed cluster identification of QTLs and QTNs, then combined QTL and QTN clusters to detect consensus hotspot regions. In total, 31 hotspots were identified for kernel size-related traits. Their candidate genes were predicted to be related to well-known pathways regulating the kernel developmental process. The identified hotspots can be further explored for fine mapping and candidate gene validation. Finally, we provided a strategy for high yield and quality maize. This study will not only facilitate causal genes cloning, but also guide the breeding practice for maize.

Identification of quantitative trait loci (QTL) and meta-QTL analysis for kernel size-related traits in wheat (Triticum aestivum L.)

BackgroundKernel size-related traits, including kernel length (KL), kernel width (KW), kernel diameter ratio (KDR) and kernel thickness (KT), are critical determinants for wheat kernel weight and yield and highly governed by a type of quantitative genetic basis. Genome-wide identification of major and stable quantitative trait loci (QTLs) and functional genes are urgently required for genetic improvement in wheat kernel yield. A hexaploid wheat population consisting of 120 recombinant inbred lines was developed to identify QTLs for kernel size-related traits under different water environments. The meta-analysis and transcriptome evaluation were further integrated to identify major genomic regions and putative candidate genes.ResultsThe analysis of variance (ANOVA) revealed more significant genotypic effects for kernel size-related traits, indicating the moderate to high heritability of 0.61–0.89. Thirty-two QTLs for kernel size-related traits were identified, explaining 3.06%—14.2% of the phenotypic variation. Eleven stable QTLs were detected in more than three water environments. The 1103 original QTLs from the 34 previous studies and the present study were employed for the MQTL analysis and refined into 58 MQTLs. The average confidence interval of the MQTLs was 3.26-fold less than that of the original QTLs. The 1864 putative candidate genes were mined within the regions of 12 core MQTLs, where 70 candidate genes were highly expressed in spikes and kernels by comprehensive analysis of wheat transcriptome data. They were involved in various metabolic pathways, such as carbon fixation in photosynthetic organisms, carbon metabolism, mRNA surveillance pathway, RNA transport and biosynthesis of secondary metabolites.ConclusionsMajor genomic regions and putative candidate genes for kernel size-related traits in wheat have been revealed by an integrative strategy with QTL linkage mapping, meta-analysis and transcriptomic assessment. The findings provide a novel insight into understanding the genetic determinants of kernel size-related traits and will be useful for the marker-assisted selection of high yield in wheat breeding.

Evaluation of synthetic hexaploid wheat (Triticum aestivum) derived RILs for kernel traits

In bread wheat (Triticum aestivum L.), kernel parameters are significant grain quality characteristics that affect yield and milling quality as well as market price. Utilization of synthetic hexaploid donor to harness the diverse alleles for broadening the genetic base is a novel breeding strategy of the bread wheat breeding programs across the globe. An experiment was conducted during winter (rabi) season 2017–18 and 2018–19 at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi to evaluate 188 recombinant inbred lines (RILs) which were derived from HD 2932 (Indian bread wheat cultivar) and Synthetic 46 (Syn 46: Synthetic hexaploid donor) to identify the effect of the synthetic hexaploid donor on kernel parameters. Kernel parameters like kernel length (KL), kernel width (KW), kernel thickness (KT) and thousand kernel weight (TKW) were studied. Syn 46 had larger kernels and a high TKW with respect to HD 2932. Significant variation for all the traits was observed in the population with transgressive segregants. In this RILs population (188) KL ranged from 5.13–7.5 mm, KW ranged of 2.26–3.9 mm, KT ranged from 2.57–3.41 mm, and of TKW ranged from 25.2–53.17 g. Correlation analysis showed a significant positive correlation of TKW with KL and KT. Potential RILs identified with desirable allelic combinations may be used for future breeding programs, and RILs with contrasting kernel parameters may be used to create nested RILs for further generation of variability.

Variety specific irrigation of almonds during hull split, effects on yield and quality

Regulated deficit irrigation (RDI) during hull-split can reduce water applied in almond orchards. Strategies for imposing RDI in almond orchards with multiple varieties with different hull-split schedules have not been extensively developed. Commonly, irrigation system design requires the same irrigation schedule for all varieties in the orchard. A 2-year study evaluated the impacts of two different regulated deficit irrigation strategies in an almond orchard with Butte, Aldrich, and Nonpareil varieties in the Sacramento Valley of California, USA. The two strategies were (1) RDI in all varieties during Nonpareil hull-split timing and (2) RDI according to variety-specific hull-split timing. The two levels of irrigation were 50 % and 75 % of potential crop evapotranspiration (ETc) replacement during the hull-split period. Results show that the kernel thickness of the Aldrich almonds increased under 75 % ETc irrigation replacement during the Aldrich hull-split period compared to 75 % ETc and 50 % ETc irrigation replacement during the Nonpareil hull-split period. In the Butte almonds, 75 % ETc and 50 % ETc irrigation replacement during variety-specific hull-split reduced the fraction of sealed shells of the Butte variety compared to 75 % ETc and 50 % ETc irrigation replacement during the Nonpareil hull-split period. This study demonstrated that an irrigation system design that allows for the independent irrigation scheduling of each variety can change the almond physical quality in the Butte and Aldrich varieties. RDI according to variety-specific hull-split did not result in significant marketable kernel yield improvements after two years of imposing the irrigation strategies. More research should be conducted for different orchard designs, varieties, and climates.

Genome-Wide Association Analysis for Candidate Genes Contributing to Kernel-Related Traits in Maize.

Maize grain size is the main factor determining grain yield. Dissecting the genetic basis of maize grain size may help reveal the regulatory mechanism of maize seed development and yield formation. In this study, two associated populations were used for genome-wide association analysis of kernel length, kernel width, kernel thickness, and hundred-kernel weight from multiple locations in AM122 and AM180, respectively. Then, genome-wide association mapping was performed based on the maize 6H90K SNP chip. A total of 139 loci were identified as associated with the four traits with p < 1 × 10−4 using two models (FarmCPU and MLM). The transcriptome data showed that 15 of them were expressed differentially in two maize-inbred lines KB182 (small kernel) and KB020 (big kernel) during kernel development. These candidate genes were enriched in regulating peroxidase activity, oxidoreductase, and leaf senescence. The molecular function was major in binding and catalytic activity. This study provided important reference information for exploring maize kernel development mechanisms and applying molecular markers in high-yield breeding.

Relationship between seed morphology, storage substance and chilling tolerance during germination of dominant maize hybrids in Northeast China

<p id="C3">Seed germination is the initial stage of crop morphology, which is determined by its own properties and environmental factors. Low temperature is one of the most important factors affecting seed germination. It is crucial to explore the relationship between seed properties and germination under low temperature environmental conditions for maize production in Northeast China. In the present study, 36 maize hybrids released in Northeast China were selected and the germination culture experiment was conducted under 6℃ (low temperature stress) and 15℃ (the control). The seedling vigor, seed germination rate, seed morphology and storage substances content were determined. The germination potential and germination rate of 36 maize hybrids were evaluated by the principal component analysis (PCA), the comprehensive evaluation value of cold tolerance (CL-value), and the membership function value (<italic>R</italic>-value). The relationship between the seed morphology (kernel length, kernel width, kernel thickness, kernel length/kernel width ratio, 100-kernel volume, and 100-kernel weight) and the seed storage substances (starch, protein, and fat) of 36 maize varieties were investigated. The results showed that the seedling vigor and germination rate of 36 maize hybrids were inhibited to some content, and the variation of relative seedling vigor cold injury rate and relative germination cold injury rate was the largest under low temperature stress. There was a significant correlation among the seven individual indicators that characterized cold tolerance. Principal component analysis could transform seven individual indicators into two independent comprehensive indicators. Among them, relative seedling vigor and relative germination rate had the largest positive contribution rate, which could be used as the key indicators for cold resistance evaluation at germination stage in maize. We classified 36 hybrids into four types of strong cold tolerance (19.4%), cold tolerance (30.6%), medium cold tolerance (33.3%), and cold sensitive (16.7%) by cluster analysis. Among them, Jidan 56, Kenji 267, Suiyu 23, Jidan 953, Kenji 268, Jidan 96, and Jidan 95 were strong cold-tolerant hybrids. The correlation analysis revealed that there was no significant correlation between seed morphology and cold tolerance. Starch content was significantly correlated with relative seedling vigor, relative germination rate, relative seedling vigor chilling injury rate, relative germination chilling injury rate, and relative germination time (<italic>r </italic>= 0.396^**, <italic>r </italic>= 0.404 ^**, <italic>r </italic>= -0.401 ^**, <italic>r </italic>= -0.391 ^**, and <italic>r </italic>= 0.362 ^**). There was a significant negative correlation between protein content and relative seedling vigor (<italic>r </italic>= -0.379^**). Regression analysis indicated that the types with high starch content had higher relative seedling vigor, relative germination rate, relative germination time, and lower relative seedling vigor, relative germination rate, and chilling injury rate. The regression model demonstrated that the seed starch content was 72.0%-74.0%, the relative seedling vigor was ≥70.0%, the relative germination rate was ≥80.5%, and the chilling injury rate of relative seedling vigor and relative germination rate was ≤50.0% under 6℃ stress. Under low temperature stress, the higher seed starch content was helpful to improve seed germination and reduce chilling injury. The varieties with starch content of 72.0%-74.0% were recommended to meet the requirements of seed germination in Northeast China.

基于全基因组关联分析解析玉米籽粒大小的遗传结构

<p id="C3">Kernel size related traits are one of the important compounds of yield, and they are also complex quantitative traits regulated by multiple genes. Mining the key regulatory genes of maize kernel size related traits will help to improve the yield. In this study, 212 excellent maize inbred lines were selected as materials. The kernel length, kernel width, and kernel thickness were measured in 2018 and 2019, respectively, and we performed genome-wide association study (GWAS) based on 73,006 single nucleotide polymorphic (SNP) markers uniformly distributed in maize genome. Based on the FarmCPU algorithm, 47 SNP markers associated with kernel size related traits were detected on 10 chromosomes in maize. Combined with the public dynamic spatio-temporal transcriptional data of kernel development of B73 maize inbred line, 58 candidate genes related to kernel size were detected in the linkage disequilibrium (LD) region marked by significant SNP. The proteins encoded by candidate genes interacted with multiple proteins and participated in and regulated many biological processes closely related to kernel development. These results provide a new reference for understanding the molecular regulation mechanism of maize kernel development, improving kernel size and increasing crop yield.

Genetic dissection of the grain-filling rate and related traits through linkage analysis and genome-wide association study in bread wheat

Wheat grain yield is generally sink-limited during grain filling. The grain-filling rate (GFR) plays a vital role but is poorly studied due to the difficulty of phenotype surveys. This study explored the grain-filling traits in a recombinant inbred population and wheat collection using two highly saturated genetic maps for linkage analysis and genome-wide association study (GWAS). Seventeen stable additive quantitative trait loci (QTLs) were identified on chromosomes 1B, 4B, and 5A. The linkage interval between IWB19555 and IWB56078 showed pleiotropic effects on GFR1, GFRmax, kernel length (KL), kernel width (KW), kernel thickness (KT), and thousand kernel weight (TKW), with the phenotypic variation explained (PVE) ranging from 13.38% (KW) to 33.69% (TKW). 198 significant marker-trait associations (MTAs) were distributed across most chromosomes except for 3D and 4D. The major associated sites for GFR included IWB44469 (11.27%), IWB8156 (12.56%) and IWB24812 (14.46%). Linkage analysis suggested that IWB35850, identified through GWAS, was located in approximately the same region as QGFRmax2B.3-11, where two high-confidence candidate genes were present. Two important grain weight (GW)-related QTLs colocalized with grain-filling QTLs. The findings contribute to understanding the genetic architecture of the GFR and provide a basic approach to predict candidate genes for grain yield trait QTLs.

Discovering Candidate Chromosomal Regions Linked to Kernel Size-Related Traits via QTL Mapping and Bulked Sample Analysis in Maize

Kernel size-related traits, including kernel length, kernel width, and kernel thickness, are critical components in determining yield and kernel quality in maize (Zea mays L.). Dissecting the phenotypic characteristics of these traits, and discovering the candidate chromosomal regions for these traits, are of potential importance for maize yield and quality improvement. In this study, a total of 139 F2:3 family lines derived from EHel and B73, a distinct line with extremely low ear height (EHel), was used for phenotyping and QTL mapping of three kernel size-related traits, including 10-kernel length (KL), 10-kernel width (KWid), and 10-kernel thickness (KT). The results showed that only one QTL for KWid, i.e., qKWid9 on Chr9, with a phenotypic variation explained (PVE) of 13.4% was detected between SNPs of AX-86298371 and AX-86298372, while no QTLs were detected for KL and KT across all 10 chromosomes. Four bulked groups of family lines, i.e., Groups I to IV, were constructed with F2:3 family lines according to the phenotypic comparisons of KWid between EHel and B73. Among these four groups, Group I possessed a significantly lower KWid than EHel (P = 0.0455), Group II was similar to EHel (P = 0.34), while both Group III and Group IV were statistically higher than EHel (P

Characterizing Selected Sorghum Grain Varieties and Evaluating the Suitability of Their Malt Extracts for Cultivating Microbial Biomass.

Microbial biomass is cultivated for different technological applications including food processing, medicine, waste management, and research. The conventional growth media used are generally expensive thus necessitating the development of more affordable alternatives. In this study, four sorghum grain varieties, SESO 1, SESO 3, Epuripur, and Eyera, and their malt extracts were characterized which is aimed at determining their suitability for growing microbial biomass. The varieties had kernel length, kernel width, kernel thickness, and thousand kernel weigh equivalent to 3.8-4.3 mm, 3.2-4.5 mm, 2.4-2.8 mm, and 12.4-20.2 g, respectively. SESO 1 and Epuripur had corneous endosperm textures whereas those of SESO 3 and Eyera were intermediate and floury, respectively. Varieties had germinative energies > 90% and total defects < 8%. SESO 3 had the highest (p < 0.05) crude protein (10.8 ± 0.3%) and dietary fiber (22.5 ± 0.4%) whereas Epuripur had the highest (p < 0.05) starch (81.6 ± 0.0%) and crude fat (2.9 ± 0.1%). There was no significant difference (p > 0.05) in the ash contents (2.1 ± 0.0%). The total sugars, free amino nitrogen, condensed tannins, and pH of the malt extracts were 106-116 g/L, 70-78 mg/L, 0.1-0.6 mg/mL, and 5.5-5.7, respectively. The composition of the sorghum malt extracts suggests their potential for use in cultivating microbial biomass.