Fusarium Seedling Blight Research Articles

Biocontrol Efficacy of Endophyte Pseudomonas poae to Alleviate Fusarium Seedling Blight by Refining the Morpho-Physiological Attributes of Wheat.

Some endophyte bacteria can improve plant growth and suppress plant diseases. However, little is known about the potential of endophytes bacteria to promote wheat growth and suppress the Fusarium seedling blight pathogen Fusarium graminearum. This study was conducted to isolate and identify endophytic bacteria and evaluate their efficacy for the plant growth promotion and disease suppression of Fusarium seedling blight (FSB) in wheat. The Pseudomonas poae strain CO showed strong antifungal activity in vitro and under greenhouse conditions against F. graminearum strain PH-1. The cell-free supernatants (CFSs) of P. poae strain CO were able to inhibit the mycelium growth, the number of colonies forming, spore germination, germ tube length, and the mycotoxin production of FSB with an inhibition rate of 87.00, 62.25, 51.33, 69.29, and 71.08%, respectively, with the highest concentration of CFSs. The results indicated that P. poae exhibited multifarious antifungal properties, such as the production of hydrolytic enzymes, siderophores, and lipopeptides. In addition, compared to untreated seeds, wheat plants treated with the strain showed significant growth rates, where root and shoot length increased by about 33% and the weight of fresh roots, fresh shoots, dry roots, and dry shoots by 50%. In addition, the strain produced high levels of indole-3-acetic acid, phosphate solubilization, and nitrogen fixation. Finally, the strain demonstrated strong antagonistic properties as well as a variety of plant growth-promoting properties. Thus, this result suggest that this strain could be used as an alternate to synthetic chemicals, which can serve as an effective method of protecting wheat from fungal infection.

Assessment of Tunisian Trichoderma Isolates on Wheat Seed Germination, Seedling Growth and Fusarium Seedling Blight Suppression.

Beneficial microorganisms, including members of the Trichoderma genus, are known for their ability to promote plant growth and disease resistance, as well as being alternatives to synthetic inputs in agriculture. In this study, 111 Trichoderma strains were isolated from the rhizospheric soil of Florence Aurore, an ancient wheat variety that was cultivated in an organic farming system in Tunisia. A preliminary ITS analysis allowed us to cluster these 111 isolates into three main groups, T. harzianum (74 isolates), T. lixii (16 isolates) and T. sp. (21 isolates), represented by six different species. Their multi-locus analysis (tef1, translation elongation factor 1; rpb2, RNA polymerase B) identified three T. afroharzianum, one T. lixii, one T. atrobrunneum and one T. lentinulae species. These six new strains were selected to determine their suitability as plant growth promoters (PGP) and biocontrol agents (BCA) against Fusarium seedling blight disease (FSB) in wheat caused by Fusarium culmorum. All of the strains exhibited PGP abilities correlated to ammonia and indole-like compound production. In terms of biocontrol activity, all of the strains inhibited the development of F. culmorum in vitro, which is linked to the production of lytic enzymes, as well as diffusible and volatile organic compounds. An in planta assay was carried out on the seeds of a Tunisian modern wheat variety (Khiar) by coating them with Trichoderma. A significant increase in biomass was observed, which is associated with increased chlorophyll and nitrogen. An FSB bioprotective effect was confirmed for all strains (with Th01 being the most effective) by suppressing morbid symptoms in germinated seeds and seedlings, as well as by limiting F. culmorum aggressiveness on overall plant growth. Plant transcriptome analysis revealed that the isolates triggered several SA- and JA-dependent defense-encoding genes involved in F. culmorum resistance in the roots and leaves of three-week-old seedlings. This finding makes these strains very promising in promoting growth and controlling FSB disease in modern wheat varieties.

Aggressiveness and mycotoxin profile of Fusarium avenaceum isolates causing Fusarium seedling blight and Fusarium head blight in UK malting barley.

Fusarium avenaceum causing Fusarium seedling blight (FSB) and Fusarium head blight (FHB) on barley is associated with economic losses of crop yield and quality, and the accumulation of mycotoxins including the enniatins (ENNs) A, A1, B and B1. Although F. avenaceum is the main producer of ENNs, studies on the ability of isolates to cause severe Fusarium diseases or produce mycotoxins in barley are limited. In this work, we investigated the aggressiveness of nine isolates of F. avenaceum to two cultivars of malting barley, Moonshine and Quench, and defined their ENN mycotoxin profiles in in vitro and in planta experiments. We assessed and compared the severity of FSB and FHB caused by these isolates to disease severity by F. graminearum, F. tricinctum and F. poae. Quantitative real-time polymerase chain reaction and Liquid Chromatography Tandem Mass Spectrometry assays were used to quantify pathogen DNA and mycotoxin accumulation, respectively, in barley heads. Isolates of F. avenaceum were equally aggressive to barley stems and heads and caused the most severe FSB symptoms resulting in up to 55% reductions of stem and root length. Fusarium graminearum caused the most severe FHB disease, followed by the isolates of F. avenaceum with the most aggressive F. avenaceum isolates capable of causing similar bleaching of barley heads as F. avenaceum. Fusarium avenaceum isolates produced ENN B as the predominant mycotoxin, followed by ENN B1 and A1 in vitro. However, only the most aggressive isolates produced ENN A1 in planta and none produced ENN A or beauvericin (BEA) either in planta or in vitro. The capacity of F. avenaceum isolates to produce ENNs was related to the accumulation of pathogen DNA in barley heads, whilst FHB severity was related to the synthesis and accumulation of ENN A1 in planta. Cv. Moonshine was significantly more resistant than Quench to FSB or FHB, caused by any Fusarium isolate, and to the accumulation of pathogen DNA, ENNs or BEA. In conclusion, aggressive F. avenaceum isolates are potent ENN producers causing severe FSB and FHB with ENN A1 requiring further investigation as potential virulence factor for F. avenaceum in cereals.

Silicon Reduces the Severity of Fusarium Infection on Young Wheat Parts In Vitro

Background: Although silicon (Si) has been referred as an essential element for controlling destructive diseases of wheat, available data are limited about enhancing adult wheat resistance against Fusarium causing head blight. Also, no reports seem to exist on the use of Si to reduce Fusarium seedling blight (FSB) on young wheat parts in vitro. Under in vitro conditions, Fusarium infection happened at the seedling stage cannot be called Fusarium head blight, because it is not a “head” disease, instead it could be called “FSB”. Objective and Methods: This research aimed to elucidate the bio-efficacy of soluble Si at 1.7 mM to increase wheat resistance to FSB measured by latent period (LP) of detached leaf inoculation, area under disease progress curve (AUDPC) of Petri-dish inoculation and coleoptile length reduction (CLR) of a coleoptile infection detected in vitro. Si treatments were applied to six bread and durum wheat cultivars of contrasting susceptibility to disease infected with four Fusarium species displaying a diverse pathogenicity. Results: Differences were observed on wheat detached leaves and seedlings in the resistance of Si-Fusarium-inoculated treatments relative to fungal-inoculated-controls, showing the beneficial role played by this element in decreasing head blight disease symptoms on young plant parts under in vitro conditions. In all wheat cultivars infected with different Fusarium species, the application of Si did increase host resistance measured in vitro; 1.7 mM Si resulted in significantly higher LP and lesser AUDPC and CLR compared with controls. More importantly, Si at 1.7 mM increased host resistance of susceptible to moderately susceptible cultivars measured by LP, AUDPC and CLR to the same level of resistance exhibited by a wheat cultivar high in quantitative resistance without Si. Conclusion: This is the first report presenting the utility of three distinct in vitro bio-assays to investigate the effect of Si in the wheat- FSB pathosystem. The application of silicon to complement host resistance to head blight appears to be an effective strategy for disease management in wheat.

Investigation and Genome-Wide Association Analysis of Fusarium Seedling Blight Resistance in Chinese Elite Wheat Lines

Fusarium seedling blight (FSB) is an important disease of wheat occurring as part of the Fusarium disease complex consisting also of Fusarium head blight (FHB). 240 Chinese elite cultivars and lines were evaluated in greenhouse experiments for FSB resistance and genotyped using the wheat 90 K single nucleotide polymorphism arrays. Among them, 23 accessions had an average lesion length of less than 0.6 cm, exhibiting potential for breeding for FSB resistance in wheat. Jingfumai 1 and Yangmai 11 had a relatively high resistance to both FSB and FHB simultaneously. Six relatively stable quantitative trait loci (QTLs) were detected on chromosome arms 1DL, 3AS, 3BL, 6BL, 7AL, and Un using the mixed linear model approach, interpreting 4.83–7.53% of phenotypic variation. There was a negative correlation between the average FSB lesion length and the BLUE FHB index with a low coefficient, and resistance to both diseases appeared to be conferred by different QTLs across the same population. Four KASP markers were detected on 1DL, 3AS, 3BL, and 6BL in QTLs to facilitate marker-assisted selection. Combined with transcriptome data analysis, eight defense-related genes were considered as candidates for mapping QTLs. The resistant elite germplasm, mapped QTLs, and KASP markers developed in this study are useful resources for enhancing Fusarium seedling blight in wheat breeding.

The Effect of Agrotechnical Factors on Fusarium Mycotoxins Level in Maize

The occurrence of diseases in the cultivation of maize (Zea mays L.) leads to the loss of grain yield and the simultaneous deterioration of its quality. Fungi of the genus Fusarium spp. pose the greatest threat to maize cultivation. These fungi occur at all stages of the plant’s development, causing Fusarium seedling blight, root rot, foot rot, and ear rot, including grains. Therefore, the aim of the conducted field studies was to determine the influence of selected agriculture factors on mycotoxin contents in maize grain and ear core. Moreover, it should be noted that the presence of mycotoxins in food products in terms of legal regulations is quite a fundamental barrier both in domestic and international trade. The field experiment was carried out at the Department of Agronomy of Poznań University of Life Sciences, on the fields of the Experimental and Educational Unit in Swadzim, Poland, in 2013–2014, in four field replicates. The study involved the following factors: soil sowing preparation method, types of variates, and fertilization method, all of which shape mycotoxin accumulation. The results indicated that the main effects of years were significant for all observed traits for both the core and grain. The concentrations of deoxynivalenol, nivalenol, and zearalenone were higher in 2014 than in 2013 for both core and grain. The concentrations of fumonisin B1 and fumonisin B2 were higher in the first year of study for core and grain. The direct sowing of maize significantly affects plants’ health status, expressed by an increase in mycotoxin accumulation. Traditional hybrid SY Cooky characterized higher values of observed traits than “stay-green” hybrid Drim (except fumonisin B2 for cob). The positive effect of the row method of NP fertilizer application is based on a decrease in mycotoxin content.

Genome-Wide Identification and Characterization of Fusarium graminearum-Responsive lncRNAs in Triticum aestivum.

Although the war between wheat and Fusarium has been widely investigated for years, long noncoding RNAs (lncRNAs), which have been proven to regulate important processes in the development and stress responses of plants, are still poorly known in wheat against Fusarium. Herein, we systematically reveal the roles of wheat lncRNAs in the process of Fusarium graminearum infection by high-throughput RNA sequencing. Well over 4130 of the total 4276 differentially expressed lncRNAs were already specifically expressed at 12 h postinoculation (hpi), but only 89 of these were specifically expressed at 24 hpi, indicating that the initial stage was the crucial stage for lncRNA-mediated gene regulation of wheat defense against F. graminearum. Target analysis showed the lncRNAs participated in various biological stress processes and had exclusive regulation models at different infection stages. Further H2O2 accumulation and protein ubiquitination assays supported this idea. Moreover, two lncRNAs (XLOC_302848 and XLOC_321638) were identified as Fusarium seedling blight resistance candidates by lncRNA-target expression pattern validation, and two lncRNAs (XLOC_113815, XLOC_123624) were Fusarium head blight resistance potential regulators by cross-validating the RNAseq data with the refined meta-QTL of wheat FHB resistance. These findings extend our knowledge on wheat lncRNAs response to F. graminearum attack and provide new insights for the functional and molecular research of future interactions between wheat and Fusarium.

Artificial inoculation methods for testing microorganisms as control agents of seed- and soil-borne Fusarium-seedling blight of maize

The study describes the development and employment of plant tests based on artificial inoculation of seeds or the potting substrate for evaluating the potential of microorganisms to control seedling blight of maize caused by seed- and soil-borne fusaria. Nine strains of Fusarium were isolated from maize kernels and identified morphologically and by molecular methods as belonging to the species Fusarium verticillioides, F. subglutinans, F. cerealis, F. poae and F. proliferatum. In order to determine pathogenicity, maize kernels were inoculated by immersion in suspensions of conidia of these isolates and sown in a pasteurized substrate in seed trays. Based on plant dry weight, the isolates of F. verticillioides and F. subglutinans were more pathogenic than the other isolates. Using an isolate of F. subglutinans, the efficacy of a set of 25 potential fungal and bacterial antagonists was assessed using inoculation of maize kernels by placement in mixtures of the pathogen and the antagonists. The results obtained with this methodology indicate the potential of a number of different microorganisms applied as seed treatments, including some reported previously as biocontrol agents, to control seed-borne seedling blight of maize. In order to develop a method for the testing of biocontrol agents against soil-borne attack, isolates of F. subglutinans, F. cerealis and F poae from maize kernels together with isolates of F. avenaceum, F. culmorum and F. graminearum originating from maize silage and wheat were used to artificially inoculate the potting substrate. The results showed large differences in pathogenicity, with the most aggressive isolates belonging to F. culmorum and F. graminearum.

Transcriptional analysis of wheat seedlings inoculated with Fusarium culmorum under continual exposure to disease defence inductors.

A facultative parasite of cereals, Fusarium culmorum is a soil-, air- and seed-borne fungus causing foot and root rot, fusarium seedling blight, and especially Fusarium head blight, a spike disease leading to decreased yield and mycotoxin contamination of grain. In the present study, we tested changes in expression of wheat genes (B2H2, ICS, PAL, and PR2) involved in defence against diseases. We first compared expression of the analysed genes in seedlings of non-inoculated and artificially inoculated wheat (variety Bohemia). The second part of the experiment compared expression of these genes in seedlings grown under various treatment conditions. These treatments were chosen to determine the effects of prochloraz, sodium bicarbonate, ergosterol, aescin and potassium iodide on expression of the analysed defence genes. In addition to the inoculated and non-inoculated cultivar Bohemia, we additionally examined two other varieties of wheat with contrasting resistance to Fusarium sp. infection. These were the blue aleurone layer variety Scorpion that is susceptible to Fusarium sp. infection and variety V2-49-17 with yellow endosperm and partial resistance to Fusarium sp. infection. In this manner, we were able to compare potential effects of inductors upon defence gene expression among three varieties with different susceptibility to infection but also between inoculated and non-inoculated seedlings of a single variety. The lowest infection levels were detected in the sodium bicarbonate treatment. Sodium bicarbonate had not only negative influence on Fusarium growth but also positively affected expression of plant defence genes. Expression of the four marker genes shown to be important in plant defence was significantly affected by the treatments. The greatest upregulation in comparison to the water control was identified under all treatments for the B2H2 gene. Only expression of PAL under the ergosterol and prochloraz treatments were not statistically significant.

Does in vitro selection of biocontrol agents guarantee success in planta? A study case of wheat protection against Fusarium seedling blight by soil bacteria.

Biological control is a great hope for reducing the overutilization of pesticides in agricultural soils. It often involves microorganisms or molecules produced by microorganisms that will be able to interact with either a plant or pathogens of this plant to reduce the growth of the pathogen and limit its negative impact on the host plant. When new biocontrol products are developed, strains were mostly selected based on their ability to inhibit a pathogen of interest under in vitro conditions via antagonistic effects. Strains with no in vitro effect are often discarded and not tested in planta. But is the in vitro selection of bacterial agents according to their antagonism activities towards a plant pathogen the best way to get effective biocontrol products? To answer this question, we used wheat and the fungal pathogen Fusarium graminearum as a study pathosystem model. A library of 205 soil bacteria was screened in 2 types of in vitro growth inhibition tests against F. graminearum, and in an in planta experiment. We find strains which do not have inhibition phenotypes in vitro but good efficacy in planta. Interestingly, some strains belong to species (Microbacterium, Arthrobacter, Variovorax) that are not known in the literature for their ability to protect plants against fungal pathogens. Thus, developing a biocontrol product against F. graminearum must be preferentially based on the direct screening of strains for their protective activity on wheat plants against fungal diseases, rather than on their in vitro antagonistic effects on fungal growth.

Chlorophyll a Fluorescence Parameters of Hulled and Hull-less Barley (Hordeum vulgare L.) DH Lines Inoculated with Fusarium culmorum.

Barley worldwide is affected seriously by Fusarium seedling blight (FSB) and Fusarium head blight (FHB) diseases caused by the Fusarium species. The objective of this study was to facilitate the resistance of hulled and hull-less barley at different growth stages to F. culmorum according to direct parameters: disease rating (DR), fresh weight of leaves and roots, kernel weight per spike, kernel number per spike, plump kernels, and indirect parameters - chlorophyll a fluorescence (CF). Plate assay, greenhouse and field tests were performed on 30 spring barley doubled haploid (DH) lines and their parents infected with Fusarium culmorum. Direct parameters proved that hulled genotypes show less symptoms. Most studied chlorophyll a fluorescence (CF) parameters (apart from DIo/CS – amount of energy dissipated from PSII for laboratory test, TRo/CS – amount of excitation energy trapped in PSII reaction centers, ETo/CS – amount of energy used for electron transport and RC/CS – number of active reaction centres in the state of fully reduced PSII reaction center in field experiment) were significantly affected by F. culmorum infection. In all experiments, hulled genotypes had higher values of CF parameters compared to hull-less ones. Significant correlations were detected between direct and indirect parameters and also between various environments. It was revealed that ABS/CS, TRo/CS, and RC/CS have significant positive correlation in greenhouse test and field experiment. Significant correlations suggest the possibility of applying the CF parameters in selection of barley DH lines resistant to F. culmorum infection.

Targeting the pattern-triggered immunity pathway to enhance resistance to Fusarium graminearum.

SummaryFusarium head blight (FHB) is a disease of the floral tissues of wheat and barley for which highly resistant varieties are not available. Thus, there is a need to identify genes/mechanisms that can be targeted for the control of this devastating disease. Fusarium graminearum is the primary causal agent of FHB in North America. In addition, it also causes Fusarium seedling blight. Fusarium graminearum can also cause disease in the model plant Arabidopsis thaliana. The Arabidopsis–F. graminearum pathosystem has facilitated the identification of targets for the control of disease caused by this fungus. Here, we show that resistance against F. graminearum can be enhanced by flg22, a bacterial microbe‐associated molecular pattern (MAMP). flg22‐induced resistance in Arabidopsis requires its cognate pattern recognition receptor (PRR) FLS2, and is accompanied by the up‐regulation of WRKY29. The expression of WRKY29, which is associated with pattern‐triggered immunity (PTI), is also induced in response to F. graminearum infection. Furthermore, WRKY29 is required for basal resistance as well as flg22‐induced resistance to F. graminearum. Moreover, constitutive expression of WRKY29 in Arabidopsis enhances disease resistance. The PTI pathway is also activated in response to F. graminearum infection of wheat. Furthermore, flg22 application and ectopic expression of WRKY29 enhance FHB resistance in wheat. Thus, we conclude that the PTI pathway provides a target for the control of FHB in wheat. We further show that the ectopic expression of WRKY29 in wheat results in shorter stature and early heading time, traits that are important to wheat breeding.

Identification of novel quantitative trait loci for resistance to Fusarium seedling blight caused by Microdochium majus and M. nivale in wheat

Microdochium nivale and Microdochium majus are important causal agents of Fusarium seedling blight (FSB) and Fusarium head blight (FHB) in wheat and other cereals worldwide. A doubled-haploid population derived from a cross between the winter wheat Rialto and a CIMMYT spring wheat advanced line LSP2, differing in susceptibility to FSB and FHB, was assessed for resistance against the diseases caused by individual Microdochium species under controlled environment and field conditions. A linkage map constructed with DArT and SSR markers was used to identify quantitative trait loci (QTLs) for resistance against the FSB and FHB. Single, major QTLs for resistance to FSB caused by M. majus and M. nivale were found on the chromosomes 1AL and 2BS, respectively. The total phenotypic variation accounted for by the individual QTLs ranged from 42.2% to 57.7% depending on the causal organism of the disease. QTLs for emergence rate of infected seeds with both Microdochium species were also identified on chromosomes 1B and 2DS. Three QTLs conferring FHB resistance to M. majus were mapped on chromosomes 1D, 4B and 5A, explaining a total of 35.1% of the phenotypic variance. One QTL conferring FHB resistance to M. nivale was detected on chromosome 6B and accounted for 20.7% of the total phenotypic variance. We show that QTLs for resistance to FSB and FHB caused by M. majus and M. nivale are different and likely to be species-specific, suggesting that improved resistance to the diseases of the Fusarium complex can be achieved by combining their effects through crop breeding.

Host-induced gene silencing of an essential chitin synthase gene confers durable resistance to Fusarium head blight and seedling blight in wheat.

Fusarium head blight (FHB) and Fusarium seedling blight (FSB) of wheat, caused by Fusarium pathogens, are devastating diseases worldwide. We report the expression of RNA interference (RNAi) sequences derived from an essential Fusarium graminearum (Fg) virulence gene, chitin synthase (Chs) 3b, as a method to enhance resistance of wheat plants to fungal pathogens. Deletion of Chs3b was lethal to Fg; disruption of the other Chs gene family members generated knockout mutants with diverse impacts on Fg. Comparative expression analyses revealed that among the Chs gene family members, Chs3b had the highest expression levels during Fg colonization of wheat. Three hairpin RNAi constructs corresponding to the different regions of Chs3b were found to silence Chs3b in transgenic Fg strains. Co-expression of these three RNAi constructs in two independent elite wheat cultivar transgenic lines conferred high levels of stable, consistent resistance (combined type I and II resistance) to both FHB and FSB throughout the T3 to T5 generations. Confocal microscopy revealed profoundly restricted mycelia in Fg-infected transgenic wheat plants. Presence of the three specific short interfering RNAs in transgenic wheat plants was confirmed by Northern blotting, and these RNAs efficiently down-regulated Chs3b in the colonizing Fusarium pathogens on wheat seedlings and spikes. Our results demonstrate that host-induced gene silencing of an essential fungal chitin synthase gene is an effective strategy for enhancing resistance in crop plants under field test conditions.

Visual Assessment of the Severity of Fusarium Seedling Blight (FSB) and Fusarium Head Blight (FHB) Disease in Barley

Fusarium pathogens are among the most damaging pathogens of cereals. These pathogens have the ability to attack the roots, seedlings, and flowering heads of barley and wheat plants (Simpson et al., 2004). Resulting in yield loss and head blight disease and also resulting in the contamination of grain with mycotoxins harmful to human and animal health (McMulen et al., 1997; Walter et al., 2010; Agostinelli et al., 2012). The study of Fusarium diseases, including host disease resistance and the effect of exogenous agents (chemicals, biocontrol agents, etc.), requires robust and effective methods for the assessment and quantification of visual disease symptoms. Here we describe the methods commonly used for the assessment and quantification of the severity of Fusarium seedling blight and Fusarium head blight disease.

Comparative aggressiveness of Microdochium nivale and M. majus and evaluation of screening methods for Fusarium seedling blight resistance in wheat cultivars

Microdochium majus and M. nivale are the primary agents of Fusarium seedling blight (FSB) of wheat in wet and cool crop growing regions. The differential responses and plant traits (root and stem length) of eleven wheat cultivars were evaluated using three inoculation methods with M. majus or M. nivale in soil, potato dextrose agar plate or detached leaf assay to develop a reliable screening method for the identification of resistance to FSB caused by Microdochium species in wheat. Microdochium nivale was the more aggressive FSB pathogen causing 30 % higher disease severity than M. majus and impacting significantly on root length and stem length. In contrast, M. majus was more pathogenic than M. nivale on wheat leaves reducing significantly the maximum efficiency of photosystem (PS) II (Fv’/Fm’). Fv’/Fm’ provides an estimate of the efficiency of PSII photochemistry (photosynthesis) at a given photosynthetically-active photon flux density defined as PSII operating efficiency if all PSII reaction centres were ‘open’. Regression analysis suggested that reduction in stem and/or root length and Fv’/Fm’ can be used as indicators of disease severity and for the detection of tolerance in wheat cultivars to specific diseases in the Fusarium complex. There were significant interactions between genotypes and species for the assessed disease and plant traits suggesting that resistance/tolerance mechanisms and genes maybe different to disease caused by individual Microdochium species. The most resistant cultivar to FSB identified consistently using all methods was Petrus, also known to be resistant to Fusarium head blight suggesting that this cultivar may possess useful durable resistance to more than one disease in the Fusarium disease complex.

Fusarium seedling blight of wheat and oats: effects of infection level and fungicide seed treatments on agronomic characters

The effects of seed-borne Fusarium spp. and Microdochium nivale infection in spring wheat, winter wheat, and oats in Sweden was investigated in field trials for the agronomic characters yield, thousand kernel weight, grain volume weight, gluten, protein, starch, straw strength, and plant density. Seed with high and low levels of infection was mixed to obtain six infection levels in the proportions of 100/0, 80/20, 60/40, 40/60, 20/80, and 0/100 percent. The seed was untreated or treated with Celest Extra Formula M (CEFM, difenoconazole + fludioxonil) or Celest Formula M (CFM, fludioxonil). In the field trials using untreated seed, there were significant differences between infection levels only for some agronomic characters and levels. Fungicide seed treatment with CEFM in spring wheat had no significant effect on most agronomic characters including yield. In winter wheat and oats, seed treatment with CFM increased yield by 7–11% and plant density by up to 33% while having no effect on other characters. The percentage discoloration of crown roots and stem bases due to Fusarium/Microdochium spp. was also investigated visually in winter wheat and oats and found to increase with higher infection level. Fungicide seed treatment thus mainly increased plant emergence in seed lots with low-to-moderate Fusarium/Microdochium spp. infection and had little or no effects on other agronomic characters.

Genetic Diversity and Aggressiveness of Fusarium spp. Isolated from Canola in Alberta, Canada.

Canola (Brassica napus) is one of the most economically important oilseed crops in Canada. Fusarium seedling blight is a root disease with the potential to cause severe yield reductions in canola. Fusarium spp. are commonly isolated root pathogens from fields in Alberta. Fusarium infection can also cause root rot in adult plants. In this study, 128 isolates identified as Fusarium spp. were recovered from field soils in central Alberta and from the roots of diseased canola plants with typical Fusarium seedling blight symptoms. Six species of Fusarium were identified, with Fusarium acuminatum as the predominant species (57 of 128 isolates, 44.5%). Phylogenetic analyses based on the translation elongation factor 1-α and the internal transcribed spacer sequence data were used for evaluation of genetic variations, and also used for Fusarium spp. identification in combination with morphological characteristics and polymerase chain reaction-based analyses. Based on disease ratings in pathogenicity tests, six isolates of F. avenaceum showed high aggressiveness on canola. Also, the aggressiveness varied within all Fusarium spp. No correlation was observed between aggressiveness and the geographic origin of the isolates.

Brassinosteroid Enhances Resistance to Fusarium Diseases of Barley

Fusarium pathogens are among the most damaging pathogens of cereals. These pathogens have the ability to attack the roots, seedlings, and flowering heads of barley and wheat plants with disease, resulting in yield loss and head blight disease and also resulting in the contamination of grain with mycotoxins harmful to human and animal health. There is increasing evidence that brassinosteroid (BR) hormones play an important role in plant defense against both biotic and abiotic stress agents and this study set out to determine if and how BR might affect Fusarium diseases of barley. Application of the epibrassinolide (epiBL) to heads of 'Lux' barley reduced the severity of Fusarium head blight (FHB) caused by Fusarium culmorum by 86% and reduced the FHB-associated loss in grain weight by 33%. Growth of plants in soil amended with epiBL resulted in a 28 and 35% reduction in Fusarium seedling blight (FSB) symptoms on the Lux and 'Akashinriki' barley, respectively. Microarray analysis was used to determine whether growth in epiBL-amended soil changed the transcriptional profile in stem base tissue during the early stages of FSB development. At 24 and 48 h post F. culmorum inoculation, there were 146 epiBL-responsive transcripts, the majority being from the 48-h time point (n = 118). Real-time reverse-transcription polymerase chain reaction analysis validated the results for eight transcripts, including five defense genes. The results of gene expression studies show that chromatin remodeling, hormonal signaling, photosynthesis, and pathogenesis-related genes are activated in plants as a result of growth in epiBL.

Management strategies to reduce losses caused by fusarium seedling blight of field pea

Chang, K. F., Hwang, S. F., Ahmed, H. U., Gossen, B. D., Turnbull, G. D. and Strelkov, S. E. 2013. Management strategies to reduce losses caused by fusarium seedling blight of field pea. Can. J. Plant Sci. 93: 619–625. Fusarium seedling blight can cause substantial reductions in the stand density of field pea in western Canada. In greenhouse experiments, emergence decreased and root rot severity rose with increasing inoculum density. In field trials in 2007 and 2008 near Edmonton, AB, seeding at different depths and seeding dates did not consistently affect emergence or yield in Fusarium-infested soils. In field experiments, emergence declined significantly with each increase in inoculum level. Also, seed yield were reduced at high levels of disease pressure. Treatment of seed with Apron Maxx improved emergence, nodulation and yield of treatments challenged with inoculum of F. avenaceum in both greenhouse and field experiments. This research demonstrates the need to prevent seedling blight and root rot through proper seed treatment.