Maize Inbred Lines Research Articles

Nutritional and Phytonutrient Analysis of QPM and Normal Maize Inbred Lines

Investigations were carried out to characterize twenty maize inbreds at biochemical levels among QPM and normal maize lines for their effective utilization in the breeding program. Proximate analysis was carried out to study the nutritional quality of maize inbred lines based on lysine and tryptophan levels among the two groups. The nutritional composition includes lysine, tryptophan, moisture, oil, crude protein, starch and total soluble sugars, showing significant differences between QPM and normal maize inbreds, while fibre and total ash content showed little variation. Phytonutrients showed slightly higher value for QPM lines compare to normal lines exhibiting good antioxidant capability of QPM lines. The present investigation highlights the importance of evaluating biochemical parameters when selecting parents for crossing programs. The proximate composition and antioxidant capacity were proved to be useful for nutritionally better varietal identification and to evaluate QPM and normal maize lines based on nutritional and antioxidant performance.

Approaches and progress in breeding drought-tolerant maize hybrids for tropical lowlands in west and central Africa.

Drought represents a significant production challenge to maize farmers in West and Central Africa, causing substantial economic losses. Breeders at the International Institute of Tropical Agriculture have therefore been developing drought-tolerant maize varieties to attain high grain yields in rainfed maize production zones. The present review provides a historical overview of the approaches used and progress made in developing drought-tolerant hybrids over the years. Breeders made a shift from a wide area testing approach, to the use of managed screening sites, to precisely control the intensity, and timing of drought stress for developing drought-tolerant maize varieties. These sites coupled with the use of molecular markers allowed choosing suitable donors with drought-adaptive alleles for integration into existing elite maize lines to generate new drought-tolerant inbred lines. These elite maize inbred lines have then been used to develop hybrids with enhanced tolerance to drought. Genetic gains estimates were made using performance data of drought-tolerant maize hybrids evaluated in regional trials for 11 years under managed drought stress, well-watered conditions, and across diverse rainfed environments. The results found significant linear annual yield gains of 32.72kg ha-1 under managed drought stress, 38.29kg ha-1 under well-watered conditions, and 66.57kg ha-1 across multiple rainfed field environments. Promising hybrids that deliver high grain yields were also identified for areas affected by drought and variable rainfed growing conditions. The significant genetic correlations found among the three growing conditions highlight the potential to exploit the available genetic resources and modern tools to further enhance tolerance to drought in hybrids.

Identification of Novel QTL for Mercury Accumulation in Maize Using an Enlarged SNP Panel.

Mercury (Hg) pollution not only poses a threat to the environment but also adversely affects the growth and development of plants, with potential repercussions for animals and humans through bioaccumulation in the food chain. Maize, a crucial source of food, industrial materials, and livestock feed, requires special attention in understanding the genetic factors influencing mercury accumulation. Developing maize varieties with low mercury accumulation is vital for both maize production and human health. In this study, a comprehensive genome-wide association study (GWAS) was conducted using an enlarged SNP panel comprising 1.25 million single nucleotide polymorphisms (SNPs) in 230 maize inbred lines across three environments. The analysis identified 111 significant SNPs within 78 quantitative trait loci (QTL), involving 169 candidate genes under the Q model. Compared to the previous study, the increased marker density and optimized statistical model led to the discovery of 74 additional QTL, demonstrating improved statistical power. Gene ontology (GO) enrichment analysis revealed that most genes participate in arsenate reduction and stress responses. Notably, GRMZM2G440968, which has been reported in previous studies, is associated with the significant SNP chr6.S_155668107 in axis tissue. It encodes a cysteine proteinase inhibitor, implying its potential role in mitigating mercury toxicity by inhibiting cysteine. Haplotype analyses provided further insights, indicating that lines carrying hap3 exhibited the lowest mercury content compared to other haplotypes. In summary, our study significantly enhances the statistical power of GWAS, identifying additional genes related to mercury accumulation and metabolism. These findings offer valuable insights into unraveling the genetic basis of mercury content in maize and contribute to the development of maize varieties with low mercury accumulation.

Identification of Potential Tropical Maize Inbred Lines with Early Maturity for Drought-Prone Environments

The present study was undertaken during October, 2020–January, 2021 at Maize Research Centre, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana state, India to identify potential inbred lines and hybrids with early maturity and high yield through combining ability analysis and heterosis. Six lines and four testers were crossed in L×T design to obtain 24 crosses. Evaluation of these crosses and their parents for combining ability revealed significant differences due to lines, testers and their crosses indicating the existence of wider variability among the material used in the study. Maize line MGC 434 (91 days), two testers GP-170 and PFSR-56 (91 days), and one hybrid MGC-445×PFSR-132 (83 days) were identified as early duration genotypes. Four lines MGC-444 (-3.13), MGC-440 (-2.71), MGC-439 (-1.96) and MGC-445 (-0.46) with significant negative GCA effects were identified as best general combiners for early maturity. Eight hybrids, MGC-439×BML-14 (-4.99), MGC-445×PFSR-56 (-4.65), MGC-461×PFSR-56 (-3.65), MGC-445×PFSR-132 (-3.60), MGC-434×BML-14 (-2.32), MGC-439×GP-170 (-2.10), MGC-440×PFSR-56 (-2.07) and MGC-440×GP-170 (-1.01) with significant negative SCA effects were considered as best cross combinations with early maturity. The inbred parents and cross combinations with early maturity identified in the study can be utilized for development of hybrids suitable to drought prone environments.

Effects of Cd Stress on Morphological and Physiological Characteristics of Maize Seedlings

Heavy metal (HM) contamination poses a serious threat to safe crop production and human health, and different maize inbred lines respond differently to cadmium (Cd) stress. However, the morphological and physiological characteristics of maize inbred lines seedlings are not clear under Cd stress. In this study, we analyzed the agronomic traits and physiological and biochemical indices of inbred maize seedlings under Cd stress in the seedling stage using the inbred lines Kui3, CML118, Mo17, B73, and B77 as the materials. These five inbred maizes were treated with five different concentrations of Cd (0, 1, 3, 5, and 7 mg L−1, respectively) were applied and the indices of the maize seedlings determined on day 15. The aboveground and belowground biomass of five maize inbred lines seedlings showed a decreasing trend under Cd stress. Leaf relative water content and SPAD values also decreased, but the overall decrease in relative water content was small, and the differences were not significant. Surprisingly, Cd stress affected the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), leading to enhanced mem-brane lipid peroxidation. The cadmium content varied greatly between varieties under Cd stress, but all of them had lower Cd content above ground than below ground, and the varieties with the highest and lowest transfer coefficients were Mo17 (0.33–0.83) and B73 (0.06–0.44), respectively. Kui3 had the greatest difference in soluble protein content under Cd stress, which showed a de-creasing trend, and the soluble sugar content was significantly decreased in general compared to that of CK. The soluble sugar content was higher than CK under Cd treatment, and the proline content of the maize seedlings of all of the inbred lines showed an increasing trend compared to CK. Overall, there were significant genotypic differences in the Cd stress response to Cd toxicity in the maize inbred lines seedlings, and, in general, this study helps us to understand the mechanism of maize inbred lines seedlings response to Cd stress. It provides a theoretical basis for the se-lection and breeding of varieties, and food safety.

Combining ability of yellow maize (Zea mays) inbred lines for yield and agronomic traits

Present study was carried out during 2021 and 2022 at Field Crops Research Institute, Agricultural Research Centre, Giza, Egypt to estimate combining ability effects of newly developed 8 yellow maize (Zea nays L.) inbred lines using diallel cross fashion. The 28 maize hybrids were obtained by half diallel crosses at Ismailia Research Station in 2021 and evaluated at 3 locations, viz. Ismailia, Sids and Sakha Research stations in 2022 for yield and agronomic traits. Experimental results revealed that crosses mean square was significant for all the studied traits. Similarly, general and specific combining ability were significant for all the traits. Parental line P8 considered to be an excellent combiner for all traits studied except for, number of days to 50% silking and number of rows characters. The hybrid P5 × P8 possessed desirable SCA effects for a great number of studied traits. Besides, it recorded the heighest mean value for grain yield (12.55 t/ha) plus lowest ear position. As result, this cross P5×P8 could be recommended for releasing after extensive evaluation.

Genetic diversity among maize (Zea mays) inbred lines for methionine and yield associated traits

A study was carried out during winter (rabi) and rainy (kharif) seasons of 2020–21 at the research farm of ICAR-Indian Institute of Maize Research, Ludhiana, Punjab in which 22 maize inbred lines with varying content of methionine were evaluated to study various seeds and field parameters, and methionine content and further statistically analysed through genetic variability, principal components and hierarchical cluster analysis. Significant differences were noted among inbred lines for various traits. Broad- sense heritability analysis showed that traits exhibited more than 80% heritability, except plant height, cob height and no. of cobs. Principal component analysis showed five principal components having eigen value more than 1.00 and accounted for 82.01% of total variation. Cluster analysis distributed the inbred lines in 4 major clusters suggesting their use in breeding programmes. Correlation analysis was also studied to understand the correlation of field and yield parameters with methionine content. Plant height and cob height (0.83), no. of rows per cob and no. of seeds per row (0.76), anthesis and silking interval (0.89), specific gravity and silking interval (0.45) showed significant positive correlation. Traits including methionine, moisture, 100-kernel weight, no. of cobs, no. of rows/cob, no. of seeds/row and germination rate having higher genotypic and phenotypic coefficient of variation, heritability, and genetic advance mean can be used for further crop improvement programme.

Genetic diversity analysis and heterotic grouping of Indian white maize inbred lines using combining ability and SNP markers

AbstractMaize (Zea mays L.) is a versatile crop with high genetic yield potential and various uses. While yellow maize is primarily used for animal feed, white maize is preferred as a food by rural and tribal populations in India. However, white maize landraces suffer immensely in terms of low yield. Heterotic grouping is an excellent method to develop hybrids with increased yield potential in maize. The heterotic grouping of 78 white maize inbred lines was performed using combining ability and molecular diversity analysis. The lines were crossed with two testers, and the resulting hybrids were evaluated for grain yield at three locations representing different agroecological zones in India. The combining ability analysis based on specific combining ability effects on mean grain yield was used to classify the inbred lines into heterotic groups (HG‐A: 18 inbreds; HG‐B: 33 inbreds). Additionally, marker‐based clustering using 62,470 single nucleotide polymorphisms (SNPs) generated through genotyping by sequencing was also employed to determine the genetic relationships among these lines. The combining ability information was superimposed on marker‐based clustering data to obtain the heterotic grouping information, and two distinct HGs with 7 (HG‐1) and 18 inbred lines (HG‐2) were developed. The results of this study will contribute to the development of high‐performing white maize hybrids through the efficient utilization of clear‐cut and well‐defined HGs. Hence, the use of SNP markers along with the combining ability of inbred lines is a useful method for heterotic grouping and understanding of genetic relationships of white maize.

Gene actions and combining ability effects on grain yield and its constituent traits in inbred lines of quality protein maize

In the present study twenty-eight hybrid combinations resulting from the half-diallel mating of eight quality protein maize (QPM) inbred lines were chosen in order to examine the potential to combine and gene activity for ten yield and component attributes. As part of the All India Coordinated Research Project (AICRP) on maize during the kharif-2020 season, the experiment was done at the research farm of college of Agriculture, Odisha University of Agriculture & Technology (OUAT) Bhubaneswar, using a randomized complete block design replicated thrice. Every observation recorded was subjected to statistical evaluation and it was revealed that the mean squares derived from the general combining ability (gca) and specific combining ability (sca) were highly significant (p ≥0.01). Estimates of sca effects were greater than that of gca effects for all of the variables used in the study, suggesting to the predominance of dominant gene action. The inbred lines Q4-DQL 2221-1-1(833.792), Q2-DQL 2099 (517.658) and Q3- DQL 2159 (350.325) shows high gca effects for yield and its attributing traits due to more additive gene action thus identified as good general combiners for yield. Twelve of the twenty-eight crosses showed significant (p ≥0.01 and 0.05) positive sca effect on grain yield. The best experimental crosses for grain yield based on per se performance and sca effects were Q2 x Q8 (2106.748), Q1 x Q6 (2053.048), Q3 x Q7 (2027.082), and Q3 x Q6 (1719.884).

Evaluation of Resistance Resources and Analysis of Resistance Mechanisms of Maize to Stalk Rot Caused by Fusarium graminearum.

Stalk rot is one of the most destructive and widely distributed diseases in maize plants worldwide. Research on the performance and resistance mechanisms of maize against stem rot is constantly improving. In this study, among 120 inbred maize lines infected by Fusarium graminearum using the injection method, 4 lines (3.33%) were highly resistant to stalk rot, 28 lines (23.33%) were resistant, 57 lines (47.50%) were susceptible, and 31 lines (25.84%) were highly susceptible. The inbred lines 18N10118 and 18N10370 were the most resistant and susceptible with disease indices of 7.5 and 75.6, respectively. Treatment of resistant and susceptible maize inbred seedlings with F. graminearum showed that root hair growth of the susceptible inbred lines was significantly inhibited, and a large number of hyphae attached and adsorbed multiple conidia near the root system. However, the resistant inbred lines were delayed and inconspicuous, with only a few hyphae and spores appearing near the root system. Compared with susceptible inbred lines, resistant maize inbred line seedlings treated with F. graminearum exhibited elevated activities of catalase, phenylalanine ammonia-lyase, polyphenol oxidase, and superoxide dismutase. We identified 153 genes related to disease resistance by transcriptome analysis. The mitogen-activated protein kinase signaling and peroxisome pathways mainly regulated the resistance mechanism of maize inbred lines to F. graminearum infection. These two pathways might play an important role in the disease resistance mechanism, and the function of genes in the two pathways must be further studied, which might provide a theoretical basis for further understanding the molecular resistance mechanism of stalk rot and resistance gene mining.

Genome-Wide Association Study and Prediction of Tassel Weight of Tropical Maize Germplasm in Multi-Parent Population.

Tassel weight (TW) is a crucial agronomic trait that significantly affects pollen supply and grain yield development in maize breeding. To improve maize yield and develop new varieties, a comprehensive understanding of the genetic mechanisms underlying tassel weight is essential. In this study, tropical maize inbred lines, namely CML312, CML373, CML444, and YML46, were selected as female parents and crossed with the elite maize inbred line Ye107, which served as the common male parent, to develop a multi-parent population comprising four F8 recombinant inbred line (RIL) subpopulations. Using 6616 high-quality single nucleotide polymorphism (SNP) markers, we conducted genome-wide association analysis (GWAS) and genomic selection (GS) on 642 F8 RILs in four subpopulations across three different environments. Through GWAS, we identified 16 SNPs that were significantly associated with TW, encompassing two stable loci expressed across multiple environments. Furthermore, within the candidate regions of these SNPs, we discovered four novel candidate genes related to TW, namely Zm00001d044362, Zm00001d011048, Zm00001d011049, and Zm00001d031173 distributed on chromosomes 1, 3, and 8, which have not been previously reported. These genes are involved in processes such as signal transduction, growth and development, protein splicing, and pollen development, all of which play crucial roles in inflorescence meristem development, directly affecting TW. The co-localized SNP, S8_137379725, on chromosome 8 was situated within a 16.569 kb long terminal repeat retrotransposon (LTR-RT), located 22.819 kb upstream and 26.428 kb downstream of the candidate genes (Zm00001d011048 and Zm00001d011049). When comparing three distinct GS models, the BayesB model demonstrated the highest accuracy in predicting TW. This study establishes the theoretical foundation for future research into the genetic mechanisms underlying maize TW and the efficient breeding of high-yielding varieties with desired tassel weight through GS.

Selection of extra-early white quality protein maize (Zea mays L.) inbred lines for drought and low soil nitrogen resilient hybrid production

In West and Central Africa (WCA), drought and low soil nitrogen (low N) impede increased maize (Zea mays L.) productivity and production. Due to climate change, the two stresses usually occur together, leading to food, nutritional, and economic insecurity in the sub-region. There is, therefore, the need for the development and availability of high-yielding extra-early maturing white Quality Protein Maize (QPM) synthetics and hybrids with resilience to the prevailing stresses through the identification of superior climate smart (extra-early maturing) QPM inbreds under stress (drought and low soil N) conditions. The study was conducted to identify stress-resilient QPM inbred lines for hybrid production and assess the association between grain yield and other studied characters. During the 2012 minor and major rainy seasons, 96 extra-early white QPM inbreds and four (4) normal endosperm maize inbred checks were assessed in multi-location trials under stress and optimal conditions in Nigeria. The experiments were laid out in a 10 × 10 simple lattice design with two replications. Data were recorded on grain yield and other agronomic traits. Significant variations (p < 0.01) were detected among the inbred lines for measured characters, indicating adequate genetic variability among the inbreds to allow for selection and improvement of grain yield and other measured traits. Grain yield was interrelated with all the traits used in the selection index. Moderate to high estimates of heritability were observed for most of the measured traits under stress conditions, indicating that the traits could be easily transmitted to the progenies. Fifty-seven out of the 96 QPM inbreds evaluated exhibited varying degrees of resilience to drought and low N. The QPM inbreds with desired traits may be used as genetic resources for the incorporation of tolerance genes into QPM populations in the tropics, as well as for the development of drought and low N resilient synthetics and hybrids in WCA.

Association mapping for image‐based root traits in tropical maize under water stress in semi‐arid regions

AbstractThe root system is an organ that indicates signs of stress when a plant is subjected to water‐deficit conditions. However, its assessment is challenging. An alternative has been to obtain variables through image processing. In this way, it allows the rapid evaluation of genetic diversity panels. It contributes to identifying genomic regions or genes associated with the expression of the root system under water‐deficit conditions. Hence, a public diversity panel of 360 inbred lines of maize was evaluated under well‐watered (WW) and water stress (WS) conditions. Roots were phenotyped through image‐based processing. Then, genome‐wide association studies were conducted in WW and WS for each trait, using the Fixed and random model Circulating Probability Unification method. We found 23 genes or genomic regions with significant associations, of which eleven are exclusive to the WW condition, seven to the WS condition, and four are simultaneously associated with both WW and WS. All genomic regions related to the root system in the WS condition are associated with physiological mechanisms and molecular responses related to tolerance to water‐deficit conditions that can be explored in subsequent studies and by breeding programs to obtain varieties that are more tolerant and water efficient to this condition.

THE GENETIC DIVERSITY OF MAIZE INBRED LINES GROWN IN IRAQ USING SIMPLE SEQUENCE RECURRENT (SSR) MARKERS

This study was conducted to determine the genetic variability among maize inbred lines grown in Iraq by using Simple Sequence Recurrent (SSR) markers. For estimating the genetic relationships, 10 SSR primers were used with 10 maize inbred lines. Two hundred and sixteen alleles (bands) with a range of 13 to 41 were identified for the SSR loci. Polymorphism information content (PIC) of the 10 SSR loci ranged from 0.60% to 100%. Primers ‘umc1566’, ‘umc1542’, and ‘umc2189’ showed the maximum PIC value; by contrast, ‘umc2225’showed the lowest PIC value. The 10 maize inbreds were clustered based on the matrix of genetic similarity using the UPGMA algorithm. Cluster analysis placed the inbreds lines in three clusters based on SSR data. The studied inbreds lines divided to groups and subgroups with cluster analysis that revealed agreement with their geographical origin. The results indicated that SSR marker has a high degree of polymorphism that allows efficient identification of maize genotypes, and this could be used in determining their heterotic groups.

Genetic Variability of Tocol Content in a Genebank Collection of Temperate Maize Inbred Lines from Southeastern Europe

Maize is considered a promising candidate for biofortification through breeding, given its widespread cultivation and significance as a food crop. This cost-effective and sustainable approach could be used to increase the content of different tocol compounds, i.e., vitamin E, in maize grain due to the well-documented genetic variability. In the present study, an evaluation of the content of nine different tocol traits was performed in a genebank collection of 88 inbred lines of temperate maize grown at two locations in Croatia in 2019. A large genotypic variability within the studied material was observed for α-tocopherol, γ-tocopherol, δ-tocopherol, total tocopherols, α-/γ-tocopherol ratio, α-tocotrienol, γ-tocotrienol, total tocotrienols and total tocols with corresponding coefficients of variation of 52, 61, 51, 45, 106, 24, 54, 33 and 38%, respectively. Heritability estimates ranged from 0.66 for α-tocotrienol to 0.95 for δ-tocopherol. The content of α-tocopherol, which has the highest vitamin E activity and is therefore most interesting for selection, was not significantly correlated with either grain color or grain type. Comparison of the effects of simulated selection with an intensity of 20% on increased α-tocopherol content using the two selection criteria, absolute α-tocopherol content and α-/γ-tocopherol ratio, showed that the highest absolute α-tocopherol content was a better selection criterion. Indeed, simulated selection based on the absolute α-tocopherol content resulted in a 64% increase in this compound without significantly affecting the total tocopherols, the total tocotrienols, and the α-/γ-tocopherol ratio.

Genetic diversity among maize (Zea mays L.) inbred lines adapted to Japanese climates.

Understanding the genetic diversity of inbred lines is vital for development of superior F1 varieties. The present study aimed to analyze Japanese maize parental inbred lines and determine their genetic diversity for future breeding. Genetic analyses were conducted using multiple methods. Principal component analysis (PCA), phylogenetic trees, and Bayesian clustering reflected borders between heterotic groups according to the derivation of each inbred line. A self-pollinated line derived from a classic F1 variety and another line from an open-pollinated population from the same derivation were classified as separate components by PCA and Bayesian clustering. The result suggests that open pollination could be essential in modern breeding. Of those classified as dent or flint based on their derivation, some had a combination of all components or clusters. Therefore, the classification of inbred lines should be based on their derivation and DNA markers. The findings will be valuable for breeding and genetic studies in Japan. Additionally, these techniques may be used to obtain a more significant number of SNPs and related phenotypic data.

Genetic Diversity within a Collection of Italian Maize Inbred Lines: A Resource for Maize Genomics and Breeding

Genetic diversity is fundamental for studying the complex architecture of the traits of agronomic importance, controlled by major and minor loci. Moreover, well-characterized germplasm collections are essential tools for dissecting and analyzing genetic and phenotypic diversity in crops. A panel of 360 entries, a subset of a larger collection maintained within the GenBank at CREA Bergamo, which includes the inbreds derived from traditional Italian maize open-pollinated (OP) varieties and advanced breeding ones (Elite Inbreds), was analyzed to identify SNP markers using the tGBS® genotyping-by-sequencing technology. A total of 797,368 SNPs were found during the initial analysis. Imputation and filtering processes were carried out based on the percentage of missing data, redundant markers, and rarest allele frequencies, resulting in a final dataset of 15,872 SNP markers for which a physical map position was identified. Using this dataset, the inbred panel was characterized for linkage disequilibrium (LD), genetic diversity, population structure, and genetic relationships. LD decay at a genome-wide level indicates that the collection is a suitable resource for association mapping. Population structure analyses, which were carried out with different clustering methods, showed stable grouping statistics for four groups, broadly corresponding to ‘Insubria’, ‘Microsperma’, and ‘Scagliolino’ genotypes, with a fourth group composed prevalently of elite accessions derived from Italian and US breeding programs. Based on these results, the CREA Italian maize collection, genetically characterized in this study, can be considered an important tool for the mapping and characterization of useful traits and associated loci/alleles, to be used in maize breeding programs.

Effect of irrigation on wild and inbred maize with relation to the antioxidant status of pollens, flag leaves, and developing grains.

The investigation was carried out to evaluate the net effect of limited irrigation on the antioxidant status of pollens, flag leaves, and developing grains of wild and inbred maize lines. Teosinte pollens showed the highest activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione-s-transferase (GST), and peroxidase (POX) under stressful conditions while LM 11 showed a significant decrease in APX, CAT, GR, and GST activities. Limited irrigations increased the contents of superoxide and malondialdehyde (MDA) to maximum levels in LM 11 leaves. The pollens, leaves, and developing grains of teosinte had the highest content of total phenols. Proline was maximum in the developing grains of teosinte and CML 32 while lowest in those of LM 11. Principal component analysis showed that LM 11 genotype and the respective antioxidant enzymes were in completely opposite quadrants. Chord analysis showed that CAT activity and total phenol content in pollens, leaves, and developing grains contributed towards most of the variations observed in teosinte and might be responsible for managing the yield attributes of genotype during stress conditions. The pollens and leaves of teosinte, with significant SOD activity, further helped in optimizing plant yield, under stressful conditions. CML 32 occupied intermediate position owing to the unaffected activities of most of the antioxidant enzymes and high content of antioxidants in its tissues. It may be concluded that the overall antioxidant status of tissues decides the tolerance behavior of plants.

Heterotic analysis and yield assessment of maize (Zea mays L.) inbred lines for developing superior hybrids under sub-tropical climatic conditions

Heterotic analysis and yield assessment of maize (Zea mays L.) inbred lines for developing superior hybrids under sub-tropical climatic conditions

Physiological Mechanisms Underlying Tassel Symptom Formation in Maize Infected with Sporisorium reilianum.

Head smut is a soil-borne fungal disease caused by Sporisorium reilianum that infects maize tassels and ears. This disease poses a tremendous threat to global maize production. A previous study found markedly different and stably heritable tassel symptoms in some maize inbred lines with Sipingtou blood after infection with S. reilianum. In the present study, 55 maize inbred lines with Sipingtou blood were inoculated with S. reilianum and classified into three tassel symptom types (A, B, and C). Three maize inbred lines representing these classes (Huangzao4, Jing7, and Chang7-2, respectively) were used as test materials to investigate the physiological mechanisms of tassel formation in infected plants. Changes in enzyme activity, hormone content, and protein expression were analyzed in all three lines after infection and in control plants. The activities of peroxidase (POD), superoxide dismutase (SOD), and phenylalanine-ammonia-lyase (PAL) were increased in the three typical inbred lines after inoculation. POD and SOD activities showed similar trends between lines, with the increase percentage peaking at the V12 stage (POD: 57.06%, 63.19%, and 70.28% increases in Huangzao4, Jing7, and Chang7-2, respectively; SOD: 27.01%, 29.62%, and 47.07% in Huangzao4, Jing7, and Chang7-2, respectively. These were all higher than in the disease-resistant inbred line Mo17 at the same growth stage); this stage was found to be key in tassel symptom formation. Levels of gibberellic acid (GA3), indole-3-acetic acid (IAA), and abscisic acid (ABA) were also altered in the three typical maize inbred lines after inoculation, with changes in GA3 and IAA contents tightly correlated with tassel symptoms after S. reilianum infection. The differentially expressed proteins A5H8G4, P09233, and Q8VXG7 were associated with changes in enzyme activity, whereas P49353, P13689, and P10979 were associated with changes in hormone contents. Fungal infection caused reactive oxygen species (ROS) and nitric oxide (NO) bursts in the three typical inbred lines. This ROS accumulation caused biofilm disruption and altered host signaling pathways, whereas NO signaling triggered strong secondary metabolic responses in the host and altered the activities of defense-related enzymes. These factors together resulted in the formation of varying tassel symptoms. Thus, interactions between S. reilianum and susceptible maize materials were influenced by a variety of signals, enzymes, hormones, and metabolic cycles, encompassing a very complex regulatory network. This study preliminarily identified the physiological mechanisms leading to differences in tassel symptoms, deepening our understanding of S. reilianum-maize interactions.