Gibberella Ear Rot In Maize Research Articles

Genome-wide association study and molecular marker development for susceptibility to Gibberella ear rot in maize.

Sixty-nine quantitative trait nucleotides conferring maize resistance to Gibberella ear rot were detected, including eighteen novel loci. Four candidate genes were predicted, and four kompetitive allele-specific PCR markers were developed. Maize Gibberella ear rot (GER), caused by Fusarium graminearum, is one of the most devastating diseases in maize-growing regions worldwide. Enhancing maize cultivar resistance to this disease requires a comprehensive understanding of the genetic basis of resistance to GER. In this study, 334 maize inbred lines were phenotyped for GER resistance in five environments and genotyped using the Affymetrix CGMB56K SNP Array, and a genome-wide association study of resistance to GER was performed using a 3V multi-locus random-SNP-effect mixed linear model. A total of 69 quantitative trait nucleotides (QTNs) conferring resistance to GER were detected, and all of them explained individually less than 10% of the phenotypic variation, suggesting that resistance to GER is controlled by multiple minor-effect genetic loci. A total of 348 genes located around the 200-kb genomic region of these 69 QTNs were identified, and four of them (Zm00001d029648, Zm00001d031449, Zm00001d006397, and Zm00001d053145) were considered candidate genes conferring susceptibility to GER based on gene expression patterns. Moreover, four kompetitive allele-specific PCR markers were developed based on the non-synonymous variation of these four candidate genes and validated in two genetic populations. This study provides useful genetic resources for improving resistance to GER in maize.

Integrated analysis of transcriptomics and defense-related phytohormones to discover hub genes conferring maize Gibberella ear rot caused by Fusarium Graminearum

BackgroundGibberella ear rot (GER) is one of the most devastating diseases in maize growing areas, which directly reduces grain yield and quality. However, the underlying defense response of maize to pathogens infection is largely unknown.ResultsTo gain a comprehensive understanding of the defense response in GER resistance, two contrasting inbred lines ‘Nov-82’ and ‘H10’ were used to explore transcriptomic profiles and defense-related phytohormonal alterations during Fusarium graminearum infection. Transcriptomic analysis revealed 4,417 and 4,313 differentially expressed genes (DEGs) from the Nov-82 and H10, respectively, and 647 common DEGs between the two lines. More DEGs were obviously enriched in phenylpropanoid biosynthesis, secondary metabolites biosynthesis, metabolic process and defense-related pathways. In addition, the concentration of the defense-related phytohormones, jasmonates (JAs) and salicylates (SAs), was greatly induced after the pathogen infection. The level of JAs in H10 was more higher than in Nov-82, whereas an opposite pattern for the SA between the both lines. Integrated analysis of the DEGs and the phytohormones revealed five vital modules based on co-expression network analysis according to their correlation. A total of 12 hub genes encoding fatty acid desaturase, subtilisin-like protease, ethylene-responsive transcription factor, 1-aminocyclopropane-1-carboxylate oxidase, and sugar transport protein were captured from the key modules, indicating that these genes might play unique roles in response to pathogen infection,ConclusionsOverall, our results indicate that large number DEGs related to plant disease resistance and different alteration of defensive phytohormones were activated during F. graminearum infection, providing new insight into the defense response against pathogen invasion, in addition to the identified hub genes that can be further investigated for enhancing maize GER resistance.

Genetics and Environmental Factors Associated with Resistance to Fusarium graminearum, the Causal Agent of Gibberella Ear Rot in Maize

Maize is one of the most important food and feed sources at the worldwide level. Due to this importance, all the pathogens that can infect this crop can harm both food safety and security. Fungi are the most important pathogens in cultivated maize, and Fusarium spp. are one of the most important families. Reduction in yield and production of dangerous mycotoxins are the main effects of Fusarium spp. infection. Fusarium graminearum (part of the Fusarium graminearum species complex) is one the most important fungi that infect maize, and it is the causative agent of Gibberella ear rot (GER). The main characteristics of this species include its ability to infect various species and its varying infection pressures across different years. This fungus produces various harmful mycotoxins, such as deoxynivalenol, zearalenone, butanolide, and culmorin. Infection can start from silk channels or from ear wounds. In the first case, the environmental conditions are the most important factors, but in the second, a key role is played by the feeding action of lepidopteran larvae (in Europe, Ostrinia nubilalis). All these factors need to be taken into account to develop a successful management strategy, starting from cropping methods that can reduce the source of inoculum to the direct control of the fungus with fungicide, as well as insect control to reduce ear wounds. But, the most important factor that can reduce the effects of this fungus is the use of resistant hybrids. Different studies have highlighted different defensive methods developed by the plant to reduce fungal infections, like fast drying of silk and kernels, chemical compounds produced by the plant after infection, and mechanical protection from insects’ wounds. The aim of this paper is to review the scientific evidence of the most important management strategies against GER in maize and to highlight the genetic basis which is behind hybrid resistance to this disease, with a focus on genes and QTLs found in studies conducted across the world and with different types of maize from tropical cultivars to European flint.

Multi-parent QTL mapping reveals stable QTL conferring resistance to Gibberella ear rot in maize

Maize production is on risk by Gibberella ear rot (GER) caused by Fusarium graminearum. This is one of the most important ear rot diseases in temperate zones as it leads to yield losses and production of harmful mycotoxins. We investigated, for the first time, the potential use of Brazilian tropical maize to increase resistance levels to GER in temperate European flint germplasm by analyzing six interconnected biparental populations. We assessed GER symptoms in Brazil and in Europe in up to six environments (= location × year combinations) during the growing seasons of 2018 and 2019. We conducted multi-parent QTL and biparental QTL mapping, and identified four QTLs with additive gene action, each explaining 5.4 to 21.8% of the total genotypic variance for GER resistance. Among them, QTL q1 was stable across test environments, populations, and between inbred lines and testcrosses. The accuracies of genomic prediction ranged from 0.50 to 0.59 depending on the resistance donor and prediction model. Jointly, our study reveals the potential use of Brazilian resistance sources to increase GER resistance levels by genomics-assisted breeding.

Natural Occurrence of Maize Gibberella Ear Rot and Contamination of Grain with Mycotoxins in Association with Weather Variables.

Gibberella ear rot (GER) severity (percent area of the ear diseased) and associated grain contamination with mycotoxins were quantified in plots of 15 to 16 maize hybrids planted at 10 Ohio locations from 2015 to 2018. Deoxynivalenol (DON) was quantified in grain samples in all 4 years, whereas nivalenol, 3-acetyldeoxynivalenol, and 15-acetyldeoxynivalenol (15ADON) were quantified only in the last 2 years. Only DON and 15ADON were detected. The highest levels of GER and DON contamination were observed for 2018, followed by 2016 and 2017. No GER symptoms or DON were detected in 2015. Approximately 41% of the samples from asymptomatic ears had detectable levels of DON, and 7% of these samples from 2016 had DON > 5 ppm. Associations between DON contamination and 43 variables representing summaries of temperature (T), relative humidity (RH), rainfall (R), surface wetness, and T-RH combinations for different window lengths and positions relative to R1 growth stage were quantified with Spearman correlation coefficients (r). Fifteen-day window lengths tended to show the highest correlations. Most of the variables based on T, R, RH, and T-RH were significantly correlated with DON for the 15-day window, as well as other windows. For moisture-related variables, there generally was a negative correlation before R1, changing to a positive correlation after R1. Results showed that GER and DON can be frequently found in Ohio maize fields, with the risk of DON being associated with multiple weather variables, particularly those representing combinations of T between 15 and 30°C and RH > 80 summarized during the 3 weeks after R1.

QTL mapping of resistance to Gibberella ear rot in maize

Gibberella ear rot (GER), caused by the fungal pathogen Fusarium graminearum, is becoming one of the most prominent pathogens responsible for ear rot in maize. In this study three F2 populations, F2-C, F2-D, and F2-J, and their corresponding F2:3 families, were constructed by crossing three highly GER-resistant inbred lines—Cheng351, Dan598, and JiV203—with the susceptible line ZW18. We used this cross for genetic analysis and QTL mapping of resistance to GER. Analysis of variance of GER in the three F2 populations revealed the presence of significant differences among genotypes and between locations. The broad-sense heritability (H2) of GER resistance was estimated to be 0.68, 0.63, and 0.64 in the three F2 populations, indicating that genetic factors play a key role in the development of phenotypic variation. Seventeen QTLs conferring resistance to GER were detected in the three F2 populations, among which the QTL qRger7.1, originating from the resistant parent Cheng351, explained 20.16–41.84% of the phenotypic variation. The physical support interval of qRger7.1 exhibited approximately 2 Mb overlap with that of qRger7.2, which was derived from the resistant parent Dan598, supporting the identification of potential “hotspots” of the target QTLs. QTLs derived from the resistant parents Dan598 and JiV203 accounted for 59.67–61.28% and 65.82–66.90%, respectively, of the phenotypic variation. The GER-resistant QTLs identified in this study are useful candidates for improving the resistance to GER in maize using molecular marker-assisted selection.

Transcript Abundance Responses of Resistance Pathways of Arabidopsis thaliana to Deoxynivalenol

Mycotoxin deoxynivalenol (DON), produced by Gibberella zeae (Schwein.) Petch (teleomorph of Fusarium graminearum Schwabe) was known to be both a virulence factor in the pathogenesis of Triticum aestivum L. (wheat) and an inhibitor of Arabidopsis thaliana L. seed germination. Fusarium graminearum causes both Gibberella ear rot in maize (Zea mays L.) and Fusarium head blight (FHB) in wheat and barley. Arabidopsis thaliana was also a host for the related root rot pathogen F. virguliforme Aoki. A. thaliana seedling growth was reduced by the pathogen in a proportional response to increasing spore concentrations. Here, the changes in transcript abundances corresponding to 10,560 A. thaliana expressed sequence tags (ESTs) was compared with changes in 192 known plant defense and biotic/abiotic stress related genes in soybean roots after infestation with F. virguliforme. A parallel comparison with a set of resistance pathways involved in response to the DON toxicity in A. thaliana was performed. A. thaliana data was obtained from the AFGC depository. The variations of transcript abundances in Arabidopsis and soybean treated with pathogen suggest that both plants respond to the pathogen mainly by common, possibly global responses with some specific secondary metabolic pathways involved in defense. In contrast, DON toxin appeared to impact central metabolisms in Arabidopsis plants with significant alterations ranging from the protein metabolism to redox production. Several new putative resistance pathways involved in responding to both pathogen and DON infestation in soybean and A. thaliana were identified.

Timing of fungicide application for the control of Gibberella ear rot of maize

Gibberella ear rot (GER) of maize is of common occurrence in southern Brazil. The increased risk of the disease in this region is associated with wide adoption of no-till and seasonal weather conducive for epidemics, thus requiring fungicide applications to protect against the disease. However, limited information is available about the best timing for fungicide applications aiming at disease suppression. A two-year split-plot randomized complete block design experiment was conducted to determine whether early or late application of a fungicide at various intervals up to week relative to inoculation 5–6 days after silk emergence affects disease control. Treatments consisted of an application of a mix of three active ingredients present in two commercial formulations (azoxystrobin + cyproconazole and carbendazim) at different times relative to inoculation: 2, 4 or 6 days either prior (preventatively) or after (curatively) inoculation. The non-treated check consisted of non-sprayed plots. All plots were inoculated using the silk-channel-method by injecting 2 ml of macroconidia suspension (2 × 105 macroconidia/ml) of an aggressive F. meridionale isolate at 5–6 days after silk-emergence. The mean GER severity of the non-treated plots was 24.4 and 27.1 % for Maximus and P32R48H hybrids, respectively. Mean GER severity differed among application times for both hybrids (P < 0.0001). The application timing of 2, 4, and 6 days showed an average control efficacy of 52, 34, and 20 %, for Maximus hybrid and 40, 15, and 9 % for P32R48H hybrid. Although maize yield was not significantly improved, a fungicide application at two days around inoculation (preventative or curative) was the best fungicide application timing to reduce GER severity in matured grain, and could be incorporated into a disease management program.

First report of Fusarium boothii from pecan (Carya illinoinensis) and camel thorn (Vachellia erioloba) trees in South Africa

Fusarium boothii forms part of the Fusarium graminearum species complex (FGSC), the important grain pathogen group that causes Gibberella ear rot of maize and Fusarium head blight of wheat. It is known to infect many grain crops such as maize, wheat and barley. Moreover, this pathogen is a 15-ADON mycotoxin producer and thus of concern for stored grains and grain products. During endophyte isolations in the Hoopstad area of the two unrelated trees, pecan and camel thorn, isolates of the FGSC constituted a dominant part of the Fusarium isolates obtained. Pecan (Carya illinoinensis) is a rapidly developing industry in the semi-arid to arid regions of South Africa, while camel thorn (Vachellia erioloba) is a dominant native tree in the same areas. DNA sequence comparisons of the translation elongation factor 1-α and β-tubulin gene regions clearly showed that these isolates were F. boothii. This study thus represents the first report of this grain pathogen from unlikely tree hosts, and only the second report of a species in the FGSC from trees, the other being that of Fusarium acacia-mearnsii. The unexpected occurrence of F. boothii in hosts other than grain could represent an important gap in our understanding of the epidemiology, geographical occurrence and movement, and genetic pool of this important pathogen. It also raises the question of whether other species in the FGSC could have unexpected host associations.

Relationship between kernel drydown rate and resistance to gibberella ear rot in maize

Development of gibberella ear rot (GER) resistant genotypes in maize is important to reduce yield loss and most importantly to avoid mycotoxin contamination of food and feed. The objective of the current study was to investigate the effect of kernel drydown rate (KDD) on GER disease development and to test whether using KDD as an indirect selection trait could warrant selection gains for GER resistance. Six inbred lines with various levels of disease resistance were evaluated for GER silk and kernel resistance and KDD as line per se and testcrosses in one location over three consecutive years. From our results, the genotypes showed significant differences (P < 0.05) to GER and KDD. Heritability estimates were high for GER and were consistently higher than estimates for KDD. Genotypic correlation estimates between GER and KDD, which were averaged over the 3 years were significant (P < 0.01, 0.05) only for kernel inoculated plots and the strength of correlations increased when kernels progress towards maturity. The indirect selection efficiency of KDD as compared to direct selection for GER was less than one but was substantially higher for kernel inoculated plots. Our overall result demonstrated that fast KDD was among the factors that contribute to kernel resistance to GER however its use as an indirect selection trait was less promising. Thus, screening for GER resistance using disease inoculated nurseries still remain to be the most effective method for GER breeding.

Transcript Abundance Responses of Resistance Pathways of Arabidopsis thaliana to Deoxynivalenol

Mycotoxin deoxynivalenol (DON), produced by Gibberella zeae (Schwein.) Petch (teleomorph of Fusarium graminearum Schwabe) was known to be both a virulence factor in the pathogenesis of Triticum aestivum L. (wheat) and an inhibitor of Arabidopsis thaliana L. seed germination. Fusarium graminearum causes both Gibberella ear rot in maize (Zea mays L.) and Fusarium head blight (FHB) in wheat and barley. Arabidopsis thaliana was also a host for the related root rot pathogen F. virguliforme Aoki. A. thaliana seedling growth was reduced by the pathogen in a proportional response to increasing spore concentrations. Here, the changes in transcript abundances corresponding to 10,560 A. thaliana expressed sequence tags (ESTs) was compared with changes in 192 known plant defense and biotic/abiotic stress related genes in soybean roots after infestation with F. virguliforme. A parallel comparison with a set of resistance pathways involved in response to the DON toxicity in A. thaliana was performed. A. thaliana data was obtained from the AFGC depository. The variations of transcript abundances in Arabidopsis and soybean treated with pathogen suggest that both plants respond to the pathogen mainly by common, possibly global responses with some specific secondary metabolic pathways involved in defense. In contrast, DON toxin appeared to impact central metabolisms in Arabidopsis plants with significant alterations ranging from the protein metabolism to redox production. Several new putative resistance pathways involved in responding to both pathogen and DON infestation in soybean and A. thaliana were identified.

Nivalenol and 15‐acetyldeoxynivalenol Chemotypes of Fusarium graminearum Clade Species are Prevalent on Maize throughout China

AbstractFusarium graminearum clade species are among the main causative agents of Gibberella ear rot (GER) in maize and responsible for the various trichothecene mycotoxins accumulated in contaminated maize grains. In this study, a total of 620 isolates from diseased maize ears collected from 59 districts in 19 provinces throughout China, previously identified morphologically as Fusarium graminearum clade, was genetically characterized at the species level based on SCAR (Sequence Characterized Amplified Region) and for their potential capability of mycotoxin production using the genetic chemotyping assay. The results showed that 359 isolates were F. asiaticum (SCAR 5), which consisted of 97% nivalenol (NIV)‐chemotypes, 0.8% 3‐acetyldeoxynivalenol (3‐ADON)‐producing isolates and 2.2% 15‐acetyldeoxynivalenol (15‐ADON) producers, whereas the remaining 261 isolates were identified as F. graminearum sensu stricto (SCAR 1), all of which produced 15‐ADON mycotoxins. This high proportion of NIV producers present in F. asiaticum is different from the chemotype patterns in F. asiaticum populations isolated from wheat and barley, where DON and its acetylated chemotypes were the predominant mycotoxins. Moreover, the majority of NIV producers (59.1%) and all the 3‐ADON‐producing strains were derived from the warmer regions in southern China, whereas most of the 15‐ADON‐producing strains (78.4%) were isolated from the colder regions in northern China. Our study is the first report of NIV chemotypes of F. asiaticum and 15‐ADON chemotypes of F. graminearum sensu stricto that were associated with the GER of maize in China.

Trichothecene genotypes and chemotypes in Fusarium graminearum complex strains isolated from maize fields of northwest Argentina

Members of the Fusarium graminearum species complex (Fg complex) cause Gibberella ear rot in maize from northwest Argentina. The potential of these pathogens to contaminate maize grains with type B trichothecenes is a health risk for both humans and animals. We evaluated the reliability of multiplex PCR assays based on TRI3 and TRI12 genes, and single PCR assays based on TRI7 and TRI13 genes to infer trichothecene chemotypes of 112 strains of Fg complex collected from northwest Argentina, checking trichothecene production by chemical analysis. Single and multiplex PCR assays indicated that strains belonging to F. meridionale (87/112) had a NIV genotype. The remainder strains (25/112), which belonged to F. boothii, had a DON genotype (based on single PCR assays) or 15ADON genotype (based on multiplex PCR assays). No strains tested were incorrectly diagnosed with a DON/NIV genotype. Chemical analysis indicated that the F. meridionale strains were NIV producers only (44/87), major NIV producers with unexpected high DON/NIV ratios (36/87), or unexpected major DON producers with minor NIV production (7/87). Strains with atypical DON/NIV production seem to be new phenotypes under a putative NIV genotype, since PCR assays do not provide evidences of a new trichothecene genotype. DON production and absence of its acetylated forms were shown for strains of F. boothii. The inconsistencies between genetic and chemical data highlight the risk of inferring the trichothecenes potentially contaminating food and feedstuffs based only on PCR assays. This study confirms for the first time that strains of Fg complex from maize of northwest Argentina are DON and NIV producers. In addition, dominance of NIV producers in the Fg complex population isolated from maize is unprecedented in Argentina, and of significant concern to food safety and animal production.

Analysis of the Fusariumgraminearum species complex from wheat, barley and maize in South Africa provides evidence of species-specific differences in host preference

Species identity and trichothecene toxin potential of 560 members of the Fusarium graminearum species complex (FGSC) collected from diseased wheat, barley and maize in South Africa was determined using a microsphere-based multilocus genotyping assay. Although three trichothecene types (3-ADON, 15-ADON and NIV) were represented among these isolates, strains with the 15-ADON type predominated on all three hosts. A significant difference, however, was identified in the composition of FGSC pathogens associated with Gibberella ear rot (GER) of maize as compared to Fusarium head blight (FHB) of wheat or barley ( P < 0.001). F. graminearum accounted for more than 85% of the FGSC isolates associated with FHB of wheat and barley ( N = 425), and was also the dominant species among isolates from maize roots ( N = 35). However, with the exception of a single isolate identified as an interspecific hybrid between Fusarium boothii and F. graminearum, GER of maize ( N = 100) was exclusively associated with F. boothii. The predominance of F. graminearum among FHB isolates, and the near exclusivity of F. boothiii among GER isolates, was observed across all cultivars, collection dates, and provinces sampled. Because these results suggest a difference in host preference among species of the FGSC, we hypothesize that F. graminearum may be less well adapted to infect maize ears than other members of the FGSC.

Genetic diversity and trichothecene chemotypes of the Fusarium graminearum clade isolated from maize in Nepal and identification of a putative new lineage

On smallholder farms in the foothills of the Himalayan Mountains in Nepal, fungi of the Fusarium graminearum clade cause Gibberella ear rot of maize and contamination with the 8-ketotrichothecenes nivalenol and deoxynivalenol. Previous DNA marker analyses of the F. graminearum clade from maize in Nepal found a high level of genetic diversity but were limited in detail or scope. The present study incorporated a collection of 251 field strains from a wide geographic distribution in Nepal and utilized sequencing of the MAT1-1-3 gene of the mating type locus to determine the number and frequency of lineages and species of the F. graminearum clade. The frequency of nivalenol and deoxynivalenol chemotypes was determined by chemical analysis and by TRI13 deletion-marker analysis. We found that Gibberella ear rot of maize in Nepal is associated with a complex of species of the F. graminearum clade - mainly Fusarium asiaticum and Fusarium meridionale, but also Fusarium boothii and a putative new lineage, which we have designated the ‘Nepal lineage’. Fusarium graminearum sensu stricto, which dominates in maize elsewhere in Asia and worldwide, was not detected in Nepal. Although nivalenol production has been associated experimentally with lower virulence in maize ear rot and wheat head blight, this collection of the F. graminearum clade from maize in Nepal is dominated (4:1) by nivalenol producers, suggesting that traits other than crop plant pathogenesis affect population structure in this complex agroecosystem.

Genetic Variation in Testcrosses and Relationship between Line per se and Testcross Performance for Resistance to Gibberella Ear Rot in Maize

ABSTRACTGibberella ear rot (GER), caused by Fusarium spp., is a major concern in maize production in Central Europe, and development of hybrid cultivars having GER resistance is an important breeding goal. The objectives of the present study were to (i) evaluate the variation in testcross performance (TP) of European maize germplasm for GER resistance and deoxynivalenol (DON) contamination, (ii) estimate variance components, heritabilities, and correlations of these traits, and (iii) examine the relationship between line per se performance (LP) and TP. Testcrosses of 30 diverse flint inbred lines with two dent inbred testers were evaluated in four environments under artificial inoculation. Data were recorded on severity of GER and concentration of DON. There was substantial GER development and the range of both traits was greater for LP than TP. Estimates of genotypic and genotype × environment interaction variances were significant for testcrosses with both testers. Genotypic variances were generally higher for LP than for TP in each testcross set. Correlations between LP and TP were moderate ( ≤ 0.57) for GER rating and DON concentration. We recommend multi‐stage selection to develop GER resistant maize hybrids based on evaluation of GER resistance under artificial inoculation for (1) LP in one environment followed by (2) TP evaluation in two to three environments. Only the most promising testcrosses should be tested for DON concentration.

A microarray-based approach for identifying genes for resistance toFusarium Graminearumin maize (Zea MaysL.)

Fusarium graminearum causes gibberella ear rot in maize. The incidence and severity of the disease is strongly influenced by environmental factors and can reach epidemic levels. The infection can result in severe reduction in crop quality because of contamination of the grain with trichothecene mycotoxins. The best strategy for control of the disease is to develop resistant hybrids. Unfortunately, most commercial maize hybrids currently grown in Canada have little or no resistance to infection by Fusarium graminearum . In a previous study, we identified several Quantitative Trait Loci ( QTL) for resistance to gibberella ear rot in maize. The focus of this work was to identify genes underlying those QTLs by using microarray-based Comparative Genomic Hybridization (CGH). The 46K maize 70-mer oligo microarray (University of Arizona) was hybridized with the Alu I digested genomic DNA from CO387 (resistant) and CG62 (susceptible) parental lines and with the pooled resistant and susceptible recombinant inbred lines from the CG62 x CO387 population. Approximately one hundred of genes (t-test) had significant hybridization intensity differences between resistant and susceptible parents and pools. Some of these genes (chitinase, protein kinase) were similar to previous gene-based markers that were identified to cosegregate with Fusarium resistance QTLs. The identified resistance genes will be converted into markers that can easily be scored to allow rapid introgression of gibberella ear rot resistance into elite germplasm.

Dispersion analysis of gibberella ear rot in maize

Dispersion analysis of gibberella ear rot in maize