Maize F1 Hybrids Research Articles

Genome-wide association analysis of four yield-related traits using a maize (Zea mays L.) F1 population.

Increasing the yield of maize F1 hybrid is one of the most important target for breeders. However, as a result of the genetic complexity and extremely low heritability, it is very difficult to directly dissect the genetic basis and molecular mechanisms of yield, and reports on genetic analysis of F1 hybrid yield are rare. Taking F1 hybrid as the research object and dividing the yield into different affect factors, this approach may be the best strategy for clarifying the genetic mechanism of yield. Therefore, in this study, a maize F1 population consisting of 300 hybrids with 17,652 single nucleotide polymorphisms (SNPs) markers was used for genome-wide association study (GWAS) to filtrate candidate genes associated with the four yield-related traits, i.e., kernel row number (KRN), kernel number per row (KNPR), ear tip-barrenness (ETB), and hundred kernel weight (HKW). Combined with the results of previous studies and functional annotation information of candidate genes, a total of six candidate genes were identified as being associated with the four traits, which were involved in plant growth and development, protein synthesis response, phytohormone biosynthesis and signal transduction. Our results improve the understanding of the genetic basis of the four yield-related traits and may be provide a new strategy for the genetic basis of maize yield.

THE EFFECT OF DIFFERENT IRRIGATION REGIMES ON THE YIELD OF MAIZE HYBRIDS

In this article, information is given on the date, number and norm of irrigation of Uzbekistan-601 ECB, NS-6010 F1 hybrids of maize, which were carried out by furrow and drip irrigation in the conditions of weakly salted meadow alluvial soils of Bukhara province, and yield data obtained from options conducted in different irrigation regimes.

Agronomic performance of maize hybrids under Aspergillus flavus inoculation in Cameroon

Maize (Zea mays L.) is a major staple crop in most of the sub-Sahara Africa (SSA) region, constrained by a multitude of plant diseases, with the ear and kernel rots being the most widespread and difficult to manage on maize. The objective of this study was to access the agronomic performance of F1 maize hybrids exposed to Aspergillus flavus, under different agro-ecological conditions, in Cameroon. A total of 120 genotypes of maize, including four commercial hybrids, were evaluated under A. flavus infection at two sites; namely Bangangte in the Western Highlands and Mbalmayo, in the Bimodal Humid Forest Zone of Cameroon. The study was conducted during 2020 - 2021 cropping seasons. Results revealed that at Bangangte site, six (89343X88094, 88099X88094, 90204XExp 124, 89246X87036, TZI-5-1171XExp 124 and 90219X1368) out of the top 20 high yielding hybrids, had significantly high (p<0.001 tolerance (0% severity) to Aspergillus ear rot infection. At Mbalmayo site, eight (8923X88094, TZI-5-1171XExp124, 89343X88094, 90219X87036, 89243X87036, 87014X88094, TZSTR1150X87036 and 89248X88094) out of the top 20 high yielding hybrids also showed significant high (P<0.001) tolerance (0% severity) to Aspergillus ear rot infection. The interaction between hybrids and location was significant (P<0.05) for all measured traits, except ear height, grain texture, ear insect damage and husk cover (P>0.05). The pooled broad sense heritability of hybrids in the two locations varied from 5% for grain texture to 92% for days to 50% physiological maturity. Grain yield was negatively correlated with Aspergillus ear rot disease incidence and severity. Hence, promising high yielding maize hybrids with appreciable tolerance to Aspergillus ear rot disease could be selected among the tested genotypes.

Transcriptome-wide identification and characterization of genes exhibit allele-specific imprinting in maize embryo and endosperm

BackgroundGenomic imprinting refers to a subset of genes that are expressed from only one parental allele during seed development in plants. Studies on genomic imprinting have revealed that intraspecific variations in genomic imprinting expression exist in naturally genetic varieties. However, there have been few studies on the functional analysis of allele-specific imprinted genes.ResultsHere, we generated three reciprocal crosses among the B73, Mo17 and CAU5 inbred lines. Based on the transcriptome-wide analysis of allele-specific expression using RNA sequencing technology, 305 allele-specific imprinting genes (ASIGs) were identified in embryos, and 655 ASIGs were identified in endosperms from three maize F1 hybrids. Of these ASIGs, most did not show consistent maternal or paternal bias between the same tissue from different hybrids or different tissues from one hybrid cross. By gene ontology (GO) analysis, five and eight categories of GO exhibited significantly higher functional enrichments for ASIGs identified in embryo and endosperm, respectively. These functional categories indicated that ASIGs are involved in intercellular nutrient transport, signaling pathways, and transcriptional regulation of kernel development. Finally, the mutation and overexpression of one ASIG (Zm305) affected the length and width of the kernel.ConclusionIn this study, our data will be helpful in gaining further knowledge of genes exhibiting allele-specific imprinting patterns in seeds. The gain- and loss-of-function phenotypes of ASIGs associated with agronomically important seed traits provide compelling evidence for ASIGs as crucial targets to optimize seed traits in crop plants.

Characterization of Genes That Exhibit Genotype-Dependent Allele-Specific Expression and Its Implications for the Development of Maize Kernel

Heterosis or hybrid vigor refers to the superior phenotypic traits of hybrids relative to their parental inbred lines. An imbalance between the expression levels of two parental alleles in the F1 hybrid has been suggested as a mechanism of heterosis. Here, based on genome-wide allele-specific expression analysis using RNA sequencing technology, 1689 genes exhibiting genotype-dependent allele-specific expression (genotype-dependent ASEGs) were identified in the embryos, and 1390 genotype-dependent ASEGs in the endosperm, of three maize F1 hybrids. Of these ASEGs, most were consistent in different tissues from one hybrid cross, but nearly 50% showed allele-specific expression from some genotypes but not others. These genotype-dependent ASEGs were mostly enriched in metabolic pathways of substances and energy, including the tricarboxylic acid cycle, aerobic respiration, and energy derivation by oxidation of organic compounds and ADP binding. Mutation and overexpression of one ASEG affected kernel size, which indicates that these genotype-dependent ASEGs may make important contributions to kernel development. Finally, the allele-specific methylation pattern on genotype-dependent ASEGs indicated that DNA methylation plays a potential role in the regulation of allelic expression for some ASEGs. In this study, a detailed analysis of genotype-dependent ASEGs in the embryo and endosperm of three different maize F1 hybrids will provide an index of genes for future research on the genetic and molecular mechanism of heterosis.

Genome-wide identification of genes enabling accurate prediction of hybrid performance from parents across environments and populations for gene-based breeding in maize

Accurate prediction of hybrid offspring complex trait phenotype from parents is paramount to enhanced plant breeding, animal breeding, and human medicine. Here we report genome-wide identification of genes enabling accurate prediction of hybrid offspring complex traits from parents using maize grain yield as the target trait. We identified 181 ZmF1GY genes enabling prediction of maize (Zea mays L.) F1 hybrid grain yield from parents and tested their utility and efficiency for predicting F1 hybrid grain yields from parents using their expressions, genic SNPs, and number of favorable alleles (NFAs), respectively. The ZmF1GY genes predicted hybrid grain yields from parents at an accuracy of 0.86, presented by correlation coefficient between predicted and observed phenotypes, within an environment, 0.74 across environments, and 0.64 across populations, outperforming genomic prediction by 27–406%, 23%, and 40%, respectively. Furthermore, we identified nine of the ZmF1GY genes containing SNPs or InDels in parents that increased or decreased hybrid grain yields by 14–46%. When the NFAs of these nine ZmF1GY genes were used for hybrid grain yield prediction from parents, they predicted hybrid grain yields at an accuracy of 0.79, outperforming genomic prediction by 21% that was based on up to tens of thousands of genome-wide SNPs. These results demonstrate the feasibility of developing a gene toolkit for a species enabling gene-based breeding across environments and populations that is much more powerful and efficient than current breeding, thereby helping secure the world’s food production. The methodology is applicable to all crops, livestock, and humans.

The genetic mechanism of heterosis utilization in maize improvement

BackgroundIn maize hybrid breeding, complementary pools of parental lines with reshuffled genetic variants are established for superior hybrid performance. To comprehensively decipher the genetics of heterosis, we present a new design of multiple linked F1 populations with 42,840 F1 maize hybrids, generated by crossing a synthetic population of 1428 maternal lines with 30 elite testers from diverse genetic backgrounds and phenotyped for agronomic traits.ResultsWe show that, although yield heterosis is correlated with the widespread, minor-effect epistatic QTLs, it may be resulted from a few major-effect additive and dominant QTLs in early developmental stages. Floral transition is probably one critical stage for heterosis formation, in which epistatic QTLs are activated by paternal contributions of alleles that counteract the recessive, deleterious maternal alleles. These deleterious alleles, while rare, epistatically repress other favorable QTLs. We demonstrate this with one example, showing that Brachytic2 represses the Ubiquitin3 locus in the maternal lines; in hybrids, the paternal allele alleviates this repression, which in turn recovers the height of the plant and enhances the weight of the ear. Finally, we propose a molecular design breeding by manipulating key genes underlying the transition from vegetative-to-reproductive growth.ConclusionThe new population design is used to dissect the genetic basis of heterosis which accelerates maize molecular design breeding by diminishing deleterious epistatic interactions.

Estimation of Heterosis and Combining Ability for Yield, Yield Component Using Line × Tester Methods in Maize (Zea Mays L.)

This study was initiated with the objective of estimating heterosis, combing ability of selected conventional maize genotypes, comparison between hybrids, parents, and testers. Ten maize genotypes were selected (three testers and seven lines). The crosses were done in a Line × Tester mating design to produce 21 F1 single spring hybrids during 2018. The experiment was conducted. At fall season 2019; thirty-one genotypes (21 crosses + 3 tester + 7 lines) were sown in Randomized Complete Block design (RCBD) with three replications at Gerdarash research station/College of Agricultural Engineering Sciences, Salahaddin University, Erbil. The analysis of variance confirmed that the mean squares due to genotypes were highly significant for all studied characters, the tester parent (Talar) showed maximum value for tasseling number, while the parent Mst4279 recorded the maximum value for no. of days to 50% tasseling and silking and no. of ears/plant. The hybrid 232Dss × Talar showed maximum positive heterosis for plant height and ear length. The general combining ability variance was higher than specific combining ability for the plant height, ear height, 300 grain weight (g) and tassel branch number. These characters were identified to be under the control of additive-gene. Generally, the superior maize F1 hybrid L1×T2 is recommended to be taken to large-scale multilocational trials prior to commercial cultivation in Kurdistan region.

Transcriptome-wide analysis of epitranscriptome and translational efficiency associated with heterosis in maize.

Heterosis has been extensively utilized to increase productivity in crops, yet the underlying molecular mechanisms remain largely elusive. Here, we generated transcriptome-wide profiles of mRNA abundance, m6A methylation, and translational efficiency from the maize F1 hybrid B73×Mo17 and its two parental lines to ascertain the contribution of each regulatory layer to heterosis at the seedling stage. We documented that although the global abundance and distribution of m6A remained unchanged, a greater number of genes had gained an m6A modification in the hybrid. Superior variations were observed at the m6A modification and translational efficiency levels when compared with mRNA abundance between the hybrid and parents. In the hybrid, the vast majority of genes with m6A modification exhibited a non-additive expression pattern, the percentage of which was much higher than that at levels of mRNA abundance and translational efficiency. Non-additive genes involved in different biological processes were hierarchically coordinated by discrete combinations of three regulatory layers. These findings suggest that transcriptional and post-transcriptional regulation of gene expression make distinct contributions to heterosis in hybrid maize. Overall, this integrated multi-omics analysis provides a valuable portfolio for interpreting transcriptional and post-transcriptional regulation of gene expression in hybrid maize, and paves the way for exploring molecular mechanisms underlying hybrid vigor.

Rapid Screening of Maize F1 Hybrids Based on Near-Infrared Spectrum and Two-Dimensional Correlation Technology

Rapid Screening of Maize F1 Hybrids Based on Near-Infrared Spectrum and Two-Dimensional Correlation Technology

Meiotic study of Zea mays ssp. mays (2n = 40) x Tripsacum dactyloides (2 n = 72) hybrid and its progeny

Maize (2n = 40) x Tripsacum dactyloides (2n = 72) F1 hybrid plants (2n = 56) were obtained by embryo rescue and induction of somatic embryogenesis/organogenesis. Hybrid plants showed Tripsacum -like phenotypes, tolerance to stresses such as NaCl salinity and low temperatures. The more frequent meiotic configurations were 28II (24%), 24II + 2IV (19%) and 26II + 1IV (12%), with an average per cell of 0.55I + 25.18II + 1.19IV. Significant differences between plants were not observed. Pollen fertility ranged from 0% to 50%. After pollination with maize or Tripsacum , 20% of F1 plants have developed viable seeds, which originated the progeny. Thirty five percent of the progeny showed 2n = 56 chromosomes and F1 like-phenotypes, which suggests they have apomictic origin. The remaining plants were fertile and they showed maize-like phenotypes and different chromosome numbers (2n = 22, 24, 26, 28 and 30), because they kept the complete maize chromosome complement and some of the Tripsacum chromosomes. Meiotic cells showed pairing between chromosomes from both parental species, which suggests the possibility of genetic recombination between them.

Phenotypic Plasticity Contributes to Maize Adaptation and Heterosis.

Plant phenotypic plasticity describes altered phenotypic performance of an individual when grown in different environments. Exploring genetic architecture underlying plant plasticity variation may help mitigate the detrimental effects of a rapidly changing climate on agriculture, but little research has been done in this area to date. In the present study, we established a population of 976 maize F1 hybrids by crossing 488 diverse inbred lines with two elite testers. Genome-wide association study identified hundreds of quantitative trait loci associated with phenotypic plasticity variation across diverse F1 hybrids, the majority of which contributed very little variance, in accordance with the polygenic nature of these traits. We identified several quantitative trait locus regions that may have been selected during the tropical-temperate adaptation process. We also observed heterosis in terms of phenotypic plasticity, in addition to the traditional genetic value differences measured between hybrid and inbred lines, and the pattern of which was affected by genetic background. Our results demonstrate a landscape of phenotypic plasticity in maize, which will aid in the understanding of its genetic architecture, its contribution to adaptation and heterosis, and how it may be exploited for future maize breeding in a rapidly changing environment.

Agronomic Traits and Yield of F1 Maize Hybrids

Dari hasil analisis heterosis terhadap peubah komponen hasil yang telah dilakukan diperoleh bahwa F1 kombinasi persilangan BSM0729S3A x BAP277991 dan BSM0729S3B x BAP277991 secara umum lebih unggul dibandingkan tetuanya. Dapat disimpulkan bahwa dari tiga kombinasi persilangan diperoleh beberapa kandidat yang berpotensi menghasilkan daya hasil tinggi untuk selanjutnya dilakukan seleksi massa (dalam rangka menghasilkan jagung komposit baru).

ИЗМЕНЧИВОСТЬ И НАСЛЕДУЕМОСТЬ РЯДА ПРИЗНАКОВ У ПРОСТЫХ ГИБРИДОВ F1 КУКУРУЗЫ ПРИ ПОНИЖЕННОЙ ТЕМПЕРАТУРЕ И В ОБЫЧНЫХ УСЛОВИЯХ

The values of heritability coefficients of parental genotypes were determined for such characters as "frequency of callus formation", "frequency of somatic embryogenesis","frequency of plant regeneration" under normal and stressful in vitro conditions in simple maize F1 hybrids. The highest value of the coefficient of heritability of maternal genotypes in traits studied in vitro was found for “frequency of somatic embryogenesis” at low temperatures. The variability and heritability of characters during the initial stages of plant development under the actionof low temperatures, as well as quantitative characteristics of the plant and male gametophyte, were evaluated. Hybrids in which the inbred lines A239 and 092 were used as maternal genotypes showed under stress higher indices of the studied traits both invitro conditions and at the seed level. For the characters “number of grains per row” and “plant height”, the highest heritability coefficients of the interaction of maternal and paternal genotypes were noted. Hybrids A239xP502 and Co125xMK159 were selected by the higher values of the studied quantitative traits. Hybrid combinations with significantly high meanings of the most of the studied characters can be used to create cold-resistant and productive corn hybrids

Investigation of combining ability and superiority percentages for yield and some related traits in yellow maize using line × tester analysis

Combining ability estimation is an important genetic attribute for maize breeders in anticipating improvement in productivity via hybridization and selection. This research was carried out to investigate the genetic structure of the 27 F1 maize hybrids established from nine lines derived from Maize Research Department and three testers, to determine general combining ability (GCA), determine crosses showing specific combining ability (SCA) and superiority percentages for crosses. Nine lines, three testers, 27 F1 hybrids and two check commercial hybrids (SC162 and SC168) were studied in randomized complete block Design (RCBD) with three replications during 2016. The results of mean squares showed that significant and highly significant for most studied traits (days to 50% tasseling, days to 50% silking, plant and ear height, ear position, ear length, no. of kernels per row, 100-kernel weight and Grain yield). Estimates of variance due to GCA and SCA and their ratio revealed predominantly non-additive gene effects for all studied traits. Lines with the best GCA effects were: P2 (line 11) and P6 (line 21) for grain yield, for testers Gm174 and Gm1021 had significant GCA effects for grain yield. The hybrids P5×Gm1021, P6×Gm1021, P7×Gm1021, P8×Gm1002, P9×Gm1002 had significant and negative SCA effects for grain yield. Crosses P1×Gm174, P2×Gm1002, P5×Gm1021, P6×Gm174, P6×Gm1021, P7×Gm1021, P8×Gm1002, P9×Gm1021 were the best combinations manifested and significant superiority percentages over than check varieties (SC162 and SC168) for most studied traits. Therefore, these hybrids may be preferred for hybrid crop development.
 Abbreviations: GCA general combining ability; SCA specific combining ability

Physiological and Proteome Responses of Korean F1 maize (Zea mays L.) Hybrids to Water-deficit Stress during Tassel Initiation

Physiological and Proteome Responses of Korean F1 maize (Zea mays L.) Hybrids to Water-deficit Stress during Tassel Initiation

Application of Beta-Glucuronidase Transient Expression for Selection of Maize Genotypes Competent for Genetic Transformation

Genetic transformation of inbred maize lines and F1 hybrids registered in Ukraine has been carried out. The study employed a biolistic method for genetic transformation of immature maize embryos that formed callus tissue and the pAHC25 vector containing the genes of phosphinothricin-N-acetyltransferase (bar) and β-glucuronidase (uidA). As a result of the transformation of callus tissue of maize genotypes, lines resistant to phosphinothricin and regenerated plants were obtained. The activity of β-glucuronidase in herbicide-resistant calli was detected. The presence of the bar gene in callus DNA was demonstrated by the PCR method. The rate of stable transformation ranged from 2.2 to 30% depending on the genotype. The relationship between the results of transient expression of the β-glucuronidase gene and stable genetic transformation was observed. The proposed protocol for genetic transformation of maize using the study of transient expression of the β-glucuronidase gene makes it possible to significantly simplify the process of selecting genotypes competent for genetic transformation and create transgenic organisms with new traits.

Variation and Inheritance of Small RNAs in Maize Inbreds and F1 Hybrids.

Small RNAs (sRNAs) regulate gene expression, play important roles in epigenetic pathways, and are hypothesized to contribute to hybrid vigor in plants. Prior investigations have provided valuable insights into associations between sRNAs and heterosis, often using a single hybrid genotype or tissue, but our understanding of the role of sRNAs and their potential value to plant breeding are limited by an incomplete picture of sRNA variation between diverse genotypes and development stages. Here, we provide a deep exploration of sRNA variation and inheritance among a panel of 108 maize (Zea mays) samples spanning five tissues from eight inbred parents and 12 hybrid genotypes, covering a spectrum of heterotic groups, genetic variation, and levels of heterosis for various traits. We document substantial developmental and genotypic influences on sRNA expression, with varying patterns for 21-nucleotide (nt), 22-nt, and 24-nt sRNAs. We provide a detailed view of the distribution of sRNAs in the maize genome, revealing a complex makeup that also shows developmental plasticity, particularly for 22-nt sRNAs. sRNAs exhibited substantially more variation between inbreds as compared with observed variation for gene expression. In hybrids, we identify locus-specific examples of nonadditive inheritance, mostly characterized as partial or complete dominance, but rarely outside the parental range. However, the global abundance of 21-nt, 22-nt, and 24-nt sRNAs varies very little between inbreds and hybrids, suggesting that hybridization affects sRNA expression principally at specific loci rather than on a global scale. This study provides a valuable resource for understanding the potential role of sRNAs in hybrid vigor.

Field Population Density Effects on Field Yield and Morphological Characteristics of Maize

The objective of this study was to evaluate the effect of population density and row spacing on field yield and other morphological characteristics of two commercial F1 maize hybrids of different biological cycle (Costanza and LG3535) in a four-year period. Field experiments were conducted in a split-split plot design, in two population densities and three types of row spacing, involving single or twin rows. Ten plants from each plot were selected randomly and plant height, ear emergence height, ear length, ear diameter, number of grain rows per ear, grains number per ear, grain weight per ear, spindle weight per ear, and spindle diameter were measured. Grain yield of each plot was measured and field yield, thousand kernel weight and bulk density were calculated. Four years of experimentation clarified that environmental conditions may distort all other effects of the factors studied. This study points out the best combination of plant density and row configuration. High populations and twin or narrow rows (50 cm) were found to be important for maximizing yield of modern maize hybrids. Differences between hybrids were not significant, although Costanza exhibited greater mean field yield performance (14,364 kg/ha). Plant density was a significant factor and yield was increasing from low to high plant population (from 13,900 to 14,527 kg/ha). Plant density and genetic materials affected thousand kernel weights that showed the highest value at low plant density (364 g). Row spacing showed a significant interaction with year. Generally, twin or narrow rows favored many characteristics, especially height characteristics. Plant height reached 320 cm and ear height reached 149 cm. Ear diameter was favored by low plant density. Some ear characteristics were found to be depended on the genotype behavior in the certain environmental conditions. For spindle weight per ear, a total interaction between years, row spacing, hybrids, and plant density was found. For spindle diameter, various significant interactions were found, including years (maximum also in 2009), row spacing, and plant density and also row spacing, hybrids, and plant density. Many correlations were found significant especially between yield and thousand kernel weight, spindle weight per ear, and ear diameter that may prove to be useful for plant breeders.

Comparative transcriptome analysis reveals important roles of nonadditive genes in maize hybrid An\u2019nong 591 under heat stress

BackgroundHeterosis is the superior performance of F1 hybrids relative to their parental lines for a wide range of traits. In this study, expression profiling and heterosis associated genes were analyzed by RNA sequencing (RNA-Seq) in seedlings of the maize hybrid An’nong 591 and its parental lines under control and heat stress conditions.ResultsThrough performing nine pairwise comparisons, the maximum number of differentially expressed genes (DEGs) was detected between the two parental lines, and the minimum number was identified between the F1 hybrid and the paternal lines under both conditions, which suggested greater genetic contribution of the paternal line to heat stress tolerance. Gene Ontology (GO) enrichment analysis of the 4518 common DEGs indicated that GO terms associated with diverse stress responses and photosynthesis were highly overrepresented in the 76 significant terms of the biological process category. A total of 3970 and 7653 genes exhibited nonadditive expression under control and heat stress, respectively. Among these genes, 2253 (56.8%) genes overlapped, suggesting that nonadditive genes tend to be conserved in expression. In addition, 5400 nonadditive genes were found to be specific for heat stress condition, and further GO analysis indicated that terms associated with stress responses were significantly overrepresented, and 60 genes were assigned to the GO term response to heat. Pathway enrichment analysis indicated that 113 genes were involved in spliceosome metabolic pathways. Nineteen of the 33 overlapping genes assigned to the GO term response to heat showed significantly higher number of alternative splicing (AS) events under heat stress than under control conditions, suggesting that AS of these genes play an important role in response to heat stress.ConclusionsThis study reveals the transcriptomic divergence of the maize F1 hybrid and its parental lines under control and heat stress conditions, and provides insight into the underlying molecular mechanisms of heterosis and the response to heat stress in maize.