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Metabolic changes in sorghum seedlings in response to Paenibacillus alvei (NAS-6G6)-induced systemic resistance against Fusarium pseudograminearum crown rot were investigated by means of untargeted ultra-high performance liquid chromatography-high definition mass spectrometry (UHPLC-HDMS). Treatment of seedlings with the plant growth-promoting rhizobacterium P. alvei at a concentration of 1 × 108 colony forming units mL−1 prior to inoculation with F. pseudograminearum lowered crown rot disease severity significantly at the highest inoculum dose of 1 × 106 spores mL−1. Intracellular metabolites were subsequently methanol-extracted from treated and untreated sorghum roots, stems and leaves at 1, 4 and 7 days post inoculation (d.p.i.) with F. pseudograminearum. The extracts were analysed on an UHPLC-HDMS platform, and the data chemometrically processed to determine metabolic profiles and signatures related to priming and induced resistance. Significant treatment-related differences in primary and secondary metabolism post inoculation with F. pseudograminearum were observed between P. alvei-primed versus naïve S. bicolor seedlings. The differential metabolic reprogramming in primed plants comprised of a quicker and/or enhanced upregulation of amino acid-, phytohormone-, phenylpropanoid-, flavonoid- and lipid metabolites in response to inoculation with F. pseudograminearum.

Fusarium crown rot (FCR), primarily caused by Fusarium pseudograminearum , poses significant threats to cereal crops worldwide. Prothioconazole is a demethylation inhibitor (DMI) fungicide used to control FCR. However, the risk of resistance in F. pseudograminearum to prothioconazole has not yet been evaluated. In this study, the sensitivity of a total of 255 F. pseudograminearum strains obtained from Henan Province, China to prothioconazole were determined by the mycelial growth inhibition. The results showed that the effective concentration to 50% growth inhibition (EC 50) of these strains ranged from 0.4228 μg/mL to 2.5284 μg/mL, with a mean EC 50 value of 1.0692 ± 0.4527 μg/mL (mean ± SD). Thirty prothioconazole-resistant mutants were obtained out of six selected sensitive parental strains by means of fungicide taming. The resistant mutants exhibited defects in vegetative growth, conidia production, and pathogenicity on wheat seedlings compared to their parental strains. Under ion, cell wall, and temperature stress conditions but not osmotic stress, all the mutants exhibited decreased growth rates compared with their parental strains, which was consistent with the control treatment. Cross-resistance test showed that there was a cross-resistance relationship between prothioconazole and four DMI fungicides, including prochloraz, metconazole, tebuconazole and hexaconazole, but no cross-resistance was observed between prothioconazole and carbendazim, phenamacril, fludioxonil, or azoxystrobin. Although no site mutation occurred on Cyp51a and Cyp51b genes, the constitutive expression level of the Cyp51a gene was significantly increased in all mutants. After being treated with prothioconazole, the Cyp51a and Cyp51b genes were significantly increased in both the resistant mutants and their parents. These results suggested that the resistance to prothioconazole of the mutants may be attributed to the changes of the relative expression level of Cyp51a and Cyp51b genes. Taken together, these results could provide a theoretical basis for the scientific use of prothioconazole in the field and fungicide resistance management strategies. [Display omitted] • Baseline sensitivity of Fusarium pseudograminearum to prothioconazole was established. • The resistant mutants exhibited defects in vegetative growth, conidia production, and pathogenicity on wheat seedlings. • Under ion, cell wall, and temperature stress conditions, all the mutants exhibited decreased growth rates. • Prothioconazole have a cross-resistance with four DMI fungicides, and no cross-resistance with other fungicides. • The resistance of F. pseudograminearum to prothioconazole may be attributed to the expression of Cyp51a and Cyp51b genes. [ABSTRACT FROM AUTHOR]

Fusarium crown rot of wheat is a serious fungal disease that occurs worldwide. The disease has been emerging in the major wheat-growing areas in China since 2010. Fusarium pseudogramineaum is the predominant causative pathogen of crown rot of wheat in China. The 14α-demethylation inhibitor (DMI) fungicide metconazole has been shown to be effective against Fusarium spp., but little is known about its specific activity against F. pseudogramineaum. Metconazole exhibited strong antifungal activities against all thirty-nine F. pseudogramineaum strains collected from the major wheat-growing areas in China. Metconazole inhibited mycelial growth and conidial germ tube elongation of F. pseudograminearum. Metconazole treatment significantly reduced the production of major toxins and the expression levels of toxin biosynthesis genes. Genome-wide transcriptional profiling of F. pseudograminearum in response to metconazole indicated that the expression of genes involved in ergosterol biosynthesis, including fungicide target genes (cyp51 genes), was significantly induced by metconazole. Nine ATP-binding cassette (ABC) transporter-encoding genes were significantly expressed in response to metconazole treatment. Reduced ergosterol production and antioxidant enzyme activities were observed after metconazole treatment. Greenhouse experiments indicated a significant reduction in crown rot occurrence in wheat after seed treatment with metconazole. This study evaluated the potential of metconazole to manage wheat crown rot and provides information to understand its antifungal activities and mechanism of action against F. pseudograminearum. [Display omitted] • F. pseudogramineaum is an emerging wheat pathogen, resulting in yield loss and food safety problem. • Metconazole inhibited fungal growth and toxin production of F. pseudograminearum strains. • RNA-Seq identified DEGs (ERG and ABC transporter genes) response to metconazole. • Metconazole seed treatment resulted in a significant reduction in crown rot occurrence. [ABSTRACT FROM AUTHOR]

Fusarium pseudograminearum is one of the major fungal pathogens that cause Fusarium crown rot (FCR) worldwide and can lead to a substantially reduced grain yield and quality. Transcription factors play an important role in regulating growth and pathogenicity in plant pathogens. In this study, we identified a putative Zn(II) 2 Cys 6 fungal-type domain-containing transcription factor and named it FpUme18. The expression of FpUME18 was induced during the infection of wheat by F. pseudograminearum . The ΔFpume18 deletion mutant showed defects in growth, conidial production, and conidial germination. In the responses to the cell wall, salt and oxidative stresses, the ΔFpume18 mutant inhibited the rate of mycelial growth at a higher rate compared with the wild type. The staining of conidia and mycelia with lipophilic dye FM4-64 revealed a delay in endocytosis when FpUME18 was deleted. FpUME18 also positively regulated the expression of phospholipid-related synthesis genes. The deletion of FpUME18 attenuated the pathogenicity of wheat coleoptiles. FpUME18 also participated in the production of the DON toxin by regulating the expression of TRI genes. Collectively, FpUme18 is required for vegetative growth, conidiation, stress response, endocytosis, and full virulence in F. pseudograminearum .

Fusarium crown rot (FCR), caused by Fusarium pseudograminearum , results in severe yield and quality losses of cereal crops in many arid and semiarid areas of the world. Limited information about the genome of F. pseudograminearum restricts the pathogenesis research and breeding of disease-resistant wheat varieties. In this study, a high-quality genome assembly of F. pseudograminearum isolate Fp22-2 was generated using Oxford Nanopore long-read sequencing technology. The assembled nuclear genome of Fp22-2 is 37.33 Mb with a repeat content of 3.69% and is divided into four contigs with a k-mer completeness score of 97.2% and a base quality accuracy of >99.99%. A total of 14,475 protein-coding genes (BUSCO completeness score, 99.9%) were predicted and functionally annotated. Moreover, genes encoding pathogenic proteins, including effector proteins and carbohydrate-active enzymes, and secondary metabolic gene clusters were identified. Overall, the high-quality genome assembly and gene annotation provided here will allow further investigation of the biology of F. pseudograminearum and lead to the development of new control options for FCR., Competing Interests: The author(s) declare no conflict of interest.

Crown and root rot of wheat caused by Fusarium pseudograminearum is one of the most important wheat diseases in Iran. In this study, the genetic structure and aggressiveness of four populations of F. pseudograminearum were investigated in five provinces of Iran. Sixty-four isolates of F. pseudograminearum, isolated from samples collected from wheat fields, were examined for genetic diversity and structure, using six simple sequence repeat markers. Fifty-eight haplotypes were identified, indicating that there was a high level of genotype diversity among Iranian isolates of F. pseudograminearum. Most of the variation (90 %) was observed within populations and only 10 % among populations. The greatest genetic similarity was detected between the Qazvin-East Azarbaijan and Lorestan populations, and the greatest genetic distance was between the populations of Lorestan and Golestan. Considerable variations in aggressiveness were observed among 40 isolates of F. pseudograminearum, which had been selected for greenhouse studies. No consistency was observed between the molecular variation and aggressiveness of the isolates. In general, the high genetic diversity accompanied with aggressiveness indicated that both of the aspects should be taken into consideration for resistant breeding program and the development of disease management strategies. [ABSTRACT FROM AUTHOR]

Chaetomium globosum is a common plant endophytic fungi that exhibits great biocontrol potential in plant disease. Fusarium crown rot (FCR) is an important disease in wheat that seriously threatens wheat production worldwide. The control effect of C. globosum against wheat FCR remains unclear. In this study, we introduced an identified C. globosum 12XP1-2-3 and tested its biological control potential against wheat FCR. The hypha and fermentation broth exhibited an antagonistic effect against Fusarium pseudograminearum . Results from indoor experiments showed that C. globosum 12XP1-2-3 might delay the onset of symptoms of brown stem base and significantly reduced the disease index (37.3%). Field trials showed that wheat seeds coated with a spore suspension of 12XP1-2-3 grew better than the control seeds, had control effects of 25.9-73.1% on FCR disease, and increased wheat yield by 3.2-11.9%. Analysis of rhizosphere microorganisms revealed that seeds coated with C. globosum ('Cg' treatment) had a greater effect on fungal rather than on bacterial alpha diversity and may improve the health state of rhizosphere microorganisms, as reflected by the significantly increased fungal Shannon index at Feekes 11 and the increased complexity of the bacterial co-occurrence network but decreased complexity of the fungal network. Moreover, the accumulation of beneficial bacteria such as Bacillus and Rhizobium at Feekes 3, and Sphingomonas at Feekes 7 in the 'Cg' treatment may be the important contributions to healthier wheat growth state, significantly reduced relative abundance of Fusarium at Feekes 11, and reduced occurrence of FCR disease. These results provide a basis for further research on the mechanism of action of C. globosum and its application in the biological control of FCR in the field., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Feng, Xu, Li, Zhang, Wang, Li, Liu, Han, Shi, Wan and Song.)

Soilborne pathogens destabilize the yields of Triticeae crops, including barley ( Hordeum vulgare L.) and wheat ( Triticum aestivum L.). Although genetic resistance derived from relatives of these species has been utilized to prevent rust diseases (i.e., in the wheat-rye 1BL-1RS translocation line), research on resistance against soilborne pathogens remains limited. Here, we performed field trials using 76 genotypes representing 28 Hordeum , six Triticum , and two Aegilops species to examine resistance against three soilborne bymoviruses: barley yellow mosaic virus (BaYMV), barley mild mosaic virus (BaMMV), and wheat yellow mosaic virus (WYMV). We also performed greenhouse tests using the soilborne fungal pathogen Fusarium pseudograminearum , which causes Fusarium crown rot (FCR). Using RT-PCR, we detected BaMMV and BaYMV in several Hordeum species, whereas WYMV induced systemic infection in the Triticum and Aegilops species. The identification of FCR susceptibility in all species examined suggests that F. pseudograminearum is a facultative fungal pathogen in Triticeae . Intraspecies variation in FCR disease severity was observed for several species, pointing to the possibility of exploring host resistance mechanisms. Therefore, by unlocking the host specificity of four soilborne pathogens in Hordeum species and their relatives, we obtained insights for the further exploration of wild sources of soilborne pathogen resistance for future wheat and barley improvement programs.

Fusarium pseudograminearum has been identified as a significant pathogen. It causes Fusarium crown rot (FCR), which occurs in several major wheat-producing areas in China. Chemical control is the primary measure with which to control this disease. In this study, transcriptome sequencing (RNA-Seq) was used to determine the different mechanisms of action of four frequently used fungicides including carbendazim, pyraclostrobin, tebuconazole, and phenamacril on F. pseudograminearum . In brief, 381, 1896, 842, and 814 differentially expressed genes (DEGs) were identified under the carbendazim, pyraclostrobin, tebuconazole, and phenamacril treatments, respectively. After the joint analysis, 67 common DEGs were obtained, and further functional analysis showed that the ABC transported pathway was significantly enriched. Moreover, FPSE_04130 ( FER6) and FPSE_11895 ( MDR1 ), two important ABC multidrug transporter genes whose expression levels simultaneously increased, were mined under the different treatments, which unambiguously demonstrated the common effects. In addition, Mfuzz clustering analysis and WGCNA analysis revealed that the core DEGs are involved in several critical pathways in each of the four treatment groups. Taken together, these genes may play a crucial function in the mechanisms of F. pseudograminearum 's response to the fungicides stress.

Cyclobutrifluram is a novel succinate dehydrogenase inhibitor (SDHI) developed by Syngenta and helps to inhibit Fusarium pseudograminearum . Here, the potential for cyclobutrifluram resistance in F. pseudograminearum and the resistance mechanism involved were evaluated. Baseline sensitivity of F. pseudograminearum to cyclobutrifluram was determined with a mean EC 50 value of 0.0248 μg/mL. Fungicide adaption generated five resistant mutants, which possess a comparable or a slightly impaired fitness compared to corresponding parental isolates. This indicates that the resistance risk of F. pseudograminearum to cyclobutrifluram might be moderate. Cyclobutrifluram-resistant isolates also demonstrated resistance to pydiflumetofen but sensitivity to carbendazim, phenamacril, tebuconazole, fludioxonil, or pyraclostrobin. Additionally, point mutations H248Y in FpSdhB and A83V or R86K in FpSdhC 1 were found in cyclobutrifluram-resistant F. pseudograminearum mutants. Molecular docking and overexpression transformation assay revealed that FpSdhB H248Y and FpSdhC 1 A83V or FpSdhC 1 R86K confer the resistance of F. pseudograminearum to cyclobutrifluram.

Crown rot, caused by Fusarium culmorum and Fusarium pseudograminearum, is one of the most pervasive diseases of wheat throughout the world . Fusarium culmorum is the most prevalent causal agent in Turkey while F. pseudograminearum is the most predominant in the USA. Consistent and reliable screening methods are required to accelerate the identification and development of wheat cultivars for resistance to Fusarium crown rot in breeding programs. A multifactor experiment with seven replicates was established investigating three different inoculation techniques (seedling dip, stem base droplet and colonized grain) using two pathogenic isolates of F. culmorum in Turkey and Fusarium pseudograminearum in the USA, respectively, against known moderately resistant and susceptible wheat cultivars under controlled greenhouse conditions. Plants were harvested and evaluated for crown rot severity using a 0-10 rating scale. Results indicated that disease severity was greater in seedling dip, compared to colonized grain, and stem base inoculation (in decreasing order of severity), respectively. However, the colonized grain method produced an adequate level of severity and consistent cultivar ranking in both experiments. Results showed significant cultivar × inoculation method interactions, and the two species of Fusarium were considered to be virulent. [ABSTRACT FROM AUTHOR]

Wheat, maize, rye and certain other agriculturally important species in the Poaceae family produce the benzoxazolinone class of phytoalexins on pest and pathogen attack. Benzoxazolinones can inhibit the growth of pathogens. However, certain fungi can actively detoxify these compounds. Despite this, a clear link between the ability to detoxify benzoxazolinones and pathogen virulence has not been shown. Here, through comparative genome analysis of several Fusarium species, we have identified a conserved genomic region around the FDB2 gene encoding an N-malonyltransferase enzyme known to be involved in benzoxazolinone degradation in the maize pathogen Fusarium verticillioides. Expression analyses demonstrated that a cluster of nine genes was responsive to exogenous benzoxazolinone in the important wheat pathogen Fusarium pseudograminearum. The analysis of independent F. pseudograminearum FDB2 knockouts and complementation of the knockout with FDB2 homologues from F. graminearum and F. verticillioides confirmed that the N-malonyltransferase enzyme encoded by this gene is central to the detoxification of benzoxazolinones, and that Fdb2 contributes quantitatively to virulence towards wheat in head blight inoculation assays. This contrasts with previous observations in F. verticillioides, where no effect of FDB2 mutations on pathogen virulence towards maize was observed. Overall, our results demonstrate that the detoxification of benzoxazolinones is a strategy adopted by wheat-infecting F. pseudograminearum to overcome host-derived chemical defences. [ABSTRACT FROM AUTHOR]

Fusarium crown rot (FCR) on wheat is a soil-borne disease that affects the yield and quality of the produce. In 2020, 297 Fusarium pseudograminearum isolates were isolated from diseased FCR wheat samples from eight regional areas across Hebei Province in China. Baseline sensitivity of F. pseudograminearum to fludioxonil (0.0613 ± 0.0347 μg/mL) and tebuconazole (0.2328 ± 0.0840 μg/mL) were constructed based on the in vitro tests of 71 and 83 isolates, respectively. The resistance index analysis showed no resistance isolate to fludioxonil but two low-resistance isolates to tebuconazole in 2020. There was an increased frequency of resistant isolates from 2021 to 2022 based on the baseline sensitivity for tebuconazole. There was no cross-resistance between fludioxonil and tebuconazole. This study provides a significant theoretical and practical basis for monitoring the resistance of F. pseudograminearum to fungicides, especially the control of FCR., Competing Interests: The authors declare that they have no competing interests., (© 2023 Zhang et al.)

Warmer temperatures associated with climate change are expected to have a direct impact on plant pathogens, challenging crops and altering plant disease profiles in the future. In this study, we have investigated the effect of increasing temperature on the pathogenic fitness of Fusarium pseudograminearum, an important necrotrophic plant pathogen associated with crown rot disease of wheat in Australia. Eleven wheat lines with different levels of crown rot resistance were artificially inoculated with F. pseudograminearum and maintained at four diurnal temperatures 15/15°C, 20/15°C, 25/15°C and 28/15°C in a controlled glasshouse. To quantify the success of F. pseudograminearum three fitness measures, these being disease severity, pathogen biomass in stem base and flag leaf node, and deoxynivalenol ( DON) in stem base and flag leaf node of mature plants were used. F. pseudograminearum showed superior overall fitness at 15/15°C, and this was reduced with increasing temperature. Pathogen fitness was significantly influenced by the level of crown rot resistance of wheat lines, but the influence of line declined with increasing temperature. Lines that exhibited superior crown rot resistance in the field were generally associated with reduced overall pathogen fitness. However, the relative performance of the wheat lines was dependent on the measure of pathogen fitness, and lines that were associated with one reduced measure of pathogen fitness did not always reduce another. There was a strong correlation between DON in stem base tissue and disease severity, but length of browning was not a good predictor of Fusarium biomass in the stem base. We report that a combination of host resistance and rising temperature will reduce pathogen fitness under increasing temperature, but further studies combining the effect of rising CO2 are essential for more realistic assessments. [ABSTRACT FROM AUTHOR]

Despite recent reports advancing our understanding of climate change on plant diseases, uncertainty remains concerning how host and pathogen interactions are changed by increases in atmospheric carbon-dioxide (CO2) and temperature. This study has observed crown rot inoculated and non-inoculated plants in three glasshouse environments comprising ambient CO2 with ambient temperature (E1), elevated CO2 with ambient temperature (E2) and elevated CO2 with warm temperatures (E3). The proportion of crown rot infected tillers (incidence), length of stem browning (severity) and biomass of Fusarium pseudograminearum in 16 wheat genotypes was destructively assessed at node development, anthesis, soft dough and crop maturity. Mean incidence, severity and Fusarium biomass was greater in E2, and all three measurements increased at a faster rate across plant development stages; E1 showed the lowest mean incidence and severity. Incidence and severity at each development stage was dependent on the environment each genotype was grown. The influence of genotype on Fusarium biomass at each development stage however was not seen to be dependent on environment. Irrespective of genotype plants with greater severity or relative Fusarium biomass showed lower plant dry weight at crop maturity in all environments with exception to E3, where CR severity did not exert a cost to plant dry weight. These results may allude to plant maturity and temperature-dependent resistance as effective mechanisms in building resistance to crown rot. Regardless of temperature, if crown rot symptoms and Fusarium biomass are to increase at elevated CO2 there is potential for a loss in crop production capability while boosting inoculum in crop stubble. [ABSTRACT FROM AUTHOR]

Existing spatiotemporal models for disease progress are unsuitable for describing epidemics of residue-borne diseases of cereals like crown rot, caused by Fusarium pseudograminearum, which increase in incidence over successive years and where inoculum has a fixed location. Monte Carlo simulation was used to explore the behaviour of a simple mechanistic model for crown rot, in which inoculum from each infected plant in one season came into contact with a defined number of plants in the following season. Contacted plants became infected according to a probability of infection that was less than 1. Growth chamber experiments confirmed that contact between infested residue and plants was required for infection. Observed features of epidemics at a long term trial site, including disease progress and maximum incidence, were satisfactorily fitted by simulations with a starting incidence of 4 %, 12 plants contacted by inoculum from each infected plant, and probability of infection of 0.66. This confirms that our understanding of disease behaviour at moderate to high levels of incidence is basically correct. However, infection rate between seasons was sensitive to initial incidence, suggesting that dispersal methods such as ascospores or conidia may be important at low incidence. A simple descriptive model was developed for the disease in bread wheat in the northern grains region of eastern Australia. Inoculum potential was estimated from the square root of the product of crown rot incidence and yield (a surrogate for biomass) of the preceding crop. Incidence of disease was related to inoculum potential by an infection constant. Crown rot inoculum was assumed to decline exponentially with time between susceptible crops. These two relationships were combined to predict the behaviour of the disease in different rotation systems. Over time, crown rot incidence converged to an equilibrium level that was determined by the infection constant, average yield, and the survival rate of inoculum. Modelled epidemics behaved in a way that was consistent with field data for continuous wheat, wheat-chickpea and wheat-sorghum rotations. This descriptive model could be used in extension or as a way of understanding how management and environment affect the disease. [ABSTRACT FROM AUTHOR]

Reliable prediction of the risk of mycotoxin contamination in post-harvest wheat will aid in improvement of the quality and safety. To establish the relationship between Fusarium pseudograminearum mycotoxins and CO 2 production, changes in their respective concentrations were monitored for the artificial contamination of wheat under different values of water activities (0.84 a w , 0.92 a w , and 0.97 a w ) and temperatures (20 ℃, 25 ℃, and 30 ℃). Water activity played a significant role in all these processes. CO 2 concentration together with moisture content and temperature were used as the main parameters to establish DON and ZEN contamination prediction models. The prediction accuracy for DON was 98.15 % (R 2  = 0.990) and 90.74 % for ZEN (R 2  = 0.982). These models were combined with T/RH/MC/CO 2 multi-parameter integrated sensors to form an early warning system, which offers a great prospect to minimise the risk of DON/ZEN contamination in post-harvest wheat., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 The Author(s).)

Fusarium crown rot (FCR), which is caused by Fusarium pseudograminearum , is one of the most important diseases affecting wheat production in the Huanghuai wheat-growing region of China. Although the phenylpyrrole fungicide fludioxonil is known to have a broad-spectrum activity against a wide range of plant pathogens, including F. pseudograminearum , it has not yet been registered for the control of FCR in China, and further research is needed to assess the biological characteristics and molecular mechanisms associated with fludioxonil resistance, and especially the potential for highly resistant isolates to emerge. The current study demonstrated that the baseline fludioxonil sensitivity of 61 F. pseudograminearum isolates collected from the Henan province of China during the summers of 2019 to 2021 conformed to a unimodal distribution with a mean effective concentration for 50% inhibition (EC 50 ) value of 0.021 ± 0.003 μg/ml, which indicated that none of the isolates exhibited natural resistance to fludioxonil. Nevertheless, four fludioxonil-resistant mutants were attained after repeated exposure to fludioxonil under laboratory conditions. All resistant mutants exhibited significantly lower growth rates on potato dextrose agar (PDA) and lower levels of sporulation and pathogenicity in wheat seedlings. In addition, the resistant mutants also exhibited less growth on PDA amended with either 0.5 M mannitol, 0.5 M glucose, 0.5 M MgCl 2 , or 0.5 M NaCl, which indicated that they had greater sensitivity to osmotic stress. Molecular analysis of the proposed fludioxonil target protein FpOs1 indicated that the predicted sequences of the resistant mutants contained none of the characteristic amino acid changes previously associated with fludioxonil resistance in other species. Further investigation via quantitative real-time PCR analysis revealed that expression of the FpOs1 gene was significantly altered in the resistant mutants in both the absence and presence of fludioxonil. Meanwhile, plate assays found evidence of cross-resistance between fludioxonil and cyprodinil, as well as with the triazole fungicides tebuconazole and difenoconazole, but not with other commonly used fungicides including prochloraz, fluazinam, and carbendazim. Taken together, these results provide new insights into the mechanism and biological characteristics associated with fludioxonil resistance in F. pseudograminearum and indicate that fludioxonil could provide effective and sustained control of FCR during wheat production.

Guanosine 3′,5′-cyclic monophosphate (cGMP) is an important signaling molecule in plants. cGMP and guanylyl cyclases (GCs), enzymes that catalyze the synthesis of cGMP from GTP, are involved in several physiological processes and responses to environmental factors, including pathogen infections. Using in vitro analysis, we demonstrated that recombinant BdGUCD1 is a protein with high guanylyl cyclase activity and lower adenylyl cyclase activity. In Brachypodium distachyon, infection by Fusarium pseudograminearum leads to changes in BdGUCD1 mRNA levels, as well as differences in endogenous cGMP levels. These observed changes may be related to alarm reactions induced by pathogen infection. As fluctuations in stress phytohormones after infection have been previously described, we performed experiments to determine the relationship between cyclic nucleotides and phytohormones. The results revealed that inhibition of cellular cGMP changes disrupts stress phytohormone content and responses to pathogen. The observations made here allow us to conclude that cGMP is an important element involved in the processes triggered as a result of infection and changes in its levels affect jasmonic acid. Therefore, stimuli-induced transient elevation of cGMP in plants may play beneficial roles in priming an optimized response, likely by triggering the mechanisms of feedback control. [ABSTRACT FROM AUTHOR]

• Trichoderma gamsii A5MH and T. harzianum Tr906 colonized wheat rhizosphere niches. • Inoculants decreased Fusarium pseudograminearum in roots and improved wheat growth. • Co-inoculation did not affect colonization, pathogen suppression or wheat growth. • All inoculant treatments impacted rhizosphere soil fungal community structure. • Strain A5MH showed consistent suppression of Fusarium crown rot between soil types. Wheat root endophytic strains Trichoderma gamsii A5MH and T. harzianum Tr906 were assessed for their abilities to suppress in planta abundance of the crown rot pathogen Fusarium pseudograminearum and increase growth of durum wheat. Fusarium crown rot suppressive assays were conducted in natural Kandosol and Chromosol wheat cropping soils with greater disease expression observed in the Chromosol. Rhizosphere abundance of T. gamsii A5MH, T. harzianum Tr906 and F. pseudograminearum were quantified by species-specific qPCR at plant maturity. Strains A5MH and Tr906 actively colonized the wheat rhizosphere and suppressed in planta pathogen abundance in both soil types, with both inoculants persisting in roots and soil to 84 days postemergence. Strain A5MH increased wheat biomass in both soils, whereas strain Tr906 only increased biomass of Chromosol-grown wheat. Metabolites of strains A5MH and Tr906 decreased in vitro growth of wheat pathogenic F. pseudograminearum , Rhizoctonia solani and Pythium irregulare , but did not inhibit either inoculant. Compared with individually inoculated strains, co-inoculation of A5MH and Tr906 did not affect rhizosphere niche abundance, in planta pathogen suppressive efficacies or wheat growth-benefits of either inoculant in Chromosol-grown wheat. Fusarium crown rot symptoms however, only decreased in the A5MH and co-inoculated treatments. Each Trichoderma treatment had distinct impacts on the structure (beta diversity) of the indigenous rhizosphere soil fungal community of Chromosol-grown wheat. Strain A5MH and co-inoculated treatments had the greatest overall effects on soil fungal community (alpha) diversity and structure. Community differentiation was primarily attributed to increased abundance of Trichoderma spp. in the inoculated treatments and associated decreases in plant pathogenic and predominantly saprophytic fungal genera. [ABSTRACT FROM AUTHOR]

Triticum turgidum ssp. durum (tetraploid durum) germplasm is very susceptible to crown rot, caused by the fungus Fusarium pseudograminearum. Screening activities to date have failed to identify even moderately susceptible lines. In contrast partial resistance to this disease has been identified in a number of Triticum aestivum (hexaploid wheat) lines, including 2-49 and Sunco. This study describes the successful introgression of partial crown rot resistance from each of these two hexaploid wheat lines into a durum wheat background. Durum backcross populations were produced from two 2-49/durum F lines which did not contain any D-genome chromosomes and which had crown rot scores similar to 2-49. F progeny of these backcross populations included lines with field based resistance to crown rot superior to that of the parent hexaploid wheat. [ABSTRACT FROM AUTHOR]

Fusarium pseudograminearum is a soilborne, hemibiotrophic phytopathogenic fungus that causes Fusarium crown rot and Fusarium head blight in wheat. The basic leucine zipper proteins (bZIPs) are evolutionarily conserved transcription factors that play crucial roles in a range of growth and developmental processes and the responses to biotic and abiotic stresses. However, the roles of bZIP transcription factors remains unknown in F. pseudograminearum . In this study, a bZIP transcription factor Fpkapc was identified to localize to the nucleus in F. pseudograminearum . A mutant strain (Δ fpkapc ) was constructed to determine the role of Fpkapc in growth and pathogenicity of F. pseudograminearum . Transcriptomic analyses revealed that many genes involved in basic metabolism and oxidation-reduction processes were downregulated, whereas many genes involved in metal iron binding were upregulated in the Δ fpkapc strain, compared with the wild type (WT). Correspondingly, the mutant had severe growth defects and displayed abnormal hyphal tips. Conidiation in the Fpkapc mutant was reduced, with more conidia in smaller size and fewer septa than in the WT. Also, relative to WT, the Δ fpkapc strain showed greater tolerance to ion stress, but decreased tolerance to H 2 O 2 . The mutant caused smaller disease lesions on wheat and barley plants, but significantly increased TRI gene expression, compared with the WT. In summary, Fpkapc plays multiple roles in governing growth, development, stress responses, and virulence in F. pseudograminearum .

Fusarium pseudograminearum is a phytopathogen that causes wheat crown rot disease worldwide. Fusarium pseudograminearum megabirnavirus 1 (FpgMBV1) was isolated from the hypovirulent strain FC136-2A of F. pseudograminearum as a novel double-stranded RNA mycovirus belonging to the family Megabirnaviridae . Here we examined the effects of FpgMBV1 on colony morphology and pathogenicity of F. pseudograminearum . Through hyphal tip culture, we obtained virus-free progeny of strain FC136-2A, referred to as FC136-2A-V - . FpgMBV1 was transferred horizontally to another virus-free strain, WZ-8A-Hyg R -V - . The progeny obtained through horizontal transfer was referred to as WZ-8A-Hyg R -V + . Colony morphology was similar between the FpgMBV1-positive and -negative strains. The ability to penetrate cellophane in vitro was lost, and pathogenicity on wheat plants was reduced significantly in the FpgMBV1-positive strains relative to the FpgMBV1-negative strains. Microscopic observations showed a 6-h delay in the formation of appressoria-like structures in FC136-2A relative to FC136-2A-V - . Mycelium extension was significantly longer in wheat coleoptiles infected by WZ-8A-Hyg R -V - than in that infected by WZ-8A-Hyg R -V + at 12 and 20 h after inoculation (hai). In addition, expression of five genes that encode cell wall-degrading enzymes differed significantly between FpgMBV1-positive and -negative strains at 12 and 20 hai during early infection of wheat cells by conidia. This study provides evidence for the hypovirulence effect of FpgMBV1 on F. pseudograminearum and suggests that the underlying mechanism involves unsuccessful early infection and perhaps cell wall degradation.

Effects of plant height on Fusarium crown rot (FCR) disease severity were investigated using 12 pairs of near-isogenic lines (NILs) for six different reduced height (Rht) genes in wheat. The dwarf isolines all gave better FCR resistance when compared with their respective tall counterparts, although the Rht genes involved in these NILs are located on several different chromosomes. Treating plants with exogenous gibberellin increased FCR severity as well as seedling lengths in all of the isolines tested. Analysis of the expression of several defense genes with known correlation with resistance to FCR pathogens between the Rht isolines following FCR inoculation indicated that the belier resistance of the dwarf isolines was not due to enhanced defense gene induction. These results suggested that the difference in FCR severity between the tall and dwarf isolines is likely due to their height difference per se or to some physiological and structural consequences of reduced height. Thus, caution should be taken when considering to exploit any FCR locus located near a height gene. [ABSTRACT FROM AUTHOR]

The article presents a study on the effects of crop rotation and split nitrogen (N) application on fusarium crown rot of wheat. For 3 years, no-till crops with split N, all N, and no-N applications and crop rotation influence were investigated and analyzed. Results show that yield and disease severity were higher in N and all N treatments than in no-N and previous crop had little but significant effect on it. It also concludes that crop rotation and N splitting had minimal effect on the disease.

Abstract: Fusarium pseudograminearum (Fp) is a stubble-borne fungus that causes crown rot in wheat and barley. Displacement of Fp from stubble by other fungi was explored. Fungi were isolated from field collections of stubble and identified using morphological and molecular methods. The most abundant species were Alternaria sp., Sterile sp. 1 and Fp. Representative isolates of all species were screened in dual culture with Fp to select candidates for detailed experiments on displacement. Trichoderma harzianum (Th), Alternaria infectoria (Ai), Fusarium equiseti (Fe) and Fusarium nygamai (Fn) were chosen as representing the range of interaction types found. The effects of temperature (5–35°C) and water potential (−0.3 to −5MPa) on growth rates, displacement of Fp from infested barley straw and dual culture interaction with Fp were determined. Th was the strongest antagonist overall, but displaced Fp very poorly at the lowest temperatures and water potentials. It was more antagonistic than expected from effects on growth at high temperature and less antagonistic than expected at low temperature. Fe and Fn showed consistent mutual antagonism with Fp on contact in dual culture and gave moderate displacement of Fp from straw, with Fe being the most effective antagonist under cool dry conditions. Ai gave very poor displacement of Fp from straw, despite being the most common straw fungus, confirming that displacement was due to antagonism and not just the presence of other fungi. The type of interaction in dual culture was consistent with degree of displacement from straw and could be used to indicate which environmental conditions were most limiting for an antagonist. The ability to displace Fp under cool dry conditions appears to be critical. [Copyright &y& Elsevier]

Wheat in eastern Oregon is produced mostly as a 2-year rotation of winter wheat and summer fallow. Maximum agronomic yield potential is expected with early September planting dates but actual yields are generally highest for plantings made in mid-October. Field experiments with sequential planting dates from early September to December were performed over 4 years. Associations among yield, disease incidence, and 19 moisture and temperature parameters were evaluated. Incidence of Cephalosporium stripe, crown rot, eyespot, and take-all decreased as planting was delayed. Crown rot and eyespot were negatively correlated more significantly and more frequently with temperature than moisture parameters, and take-all was more associated with moisture than temperature. Rhizoctonia root rot was unrelated to planting date and climatic parameters. Crown rot was identified most frequently (4 of 5 tests) as an important contributor to yield suppression but yield was most closely associated (R[sup2] > 0.96) with effects from a single disease in only two of five location-year tests. Yield was most related to combinations of diseases in three of five tests, complicating development of disease modules for wheat growth-simulation models. [ABSTRACT FROM AUTHOR]

Crown rot caused by Fusarium pseudograminearum (teleomorph: Gibberella coronicola) is a serious disease of wheat. A simple and reliable method for assessing this disease would enhance our capacity in identifying resistance sources and developing resistant wheat cultivars. In searching for such a method, several inoculation techniques were tested. One technique, soaking 1- to 4-day old seedlings in fungal spore suspension, produced consistent and severe crown rot symptoms. Glasshouse testing of several wheat genotypes using this method produced results that agreed well with previously established field ratings for crown rot disease, suggesting that this assay can be conveniently employed for screening of wheat genotypes for crown rot resistance. [ABSTRACT FROM AUTHOR]

Simple Summary: Fusarium crown rot (FCR), caused by a soil-borne fungus Fusarium pseudograminearum, is one of the most destructive diseases of cereal crops, including wheat (Triticum aestivum) in many countries. It is vital to isolate resistance genes for improving crop resistance. Herein, we report the positive function of the wheat DUF26 domain-containing receptor-like kinase TaCRK-7A in the host resistance response to the pathogen F. pseudograminearum attack. The purified TaCRK-7A protein directly inhibited F. pseudograminearum mycelial growth. The TaCRK-7A transcript was elevated upon F. pseudograminearum infection and the transcript induction was higher in resistant wheat genotypes than in susceptible wheat genotypes. Knocking down of TaCRK-7A compromised resistance of wheat to FCR and significantly reduced the transcript levels of defense genes in wheat. This study provides a novel insight into the wheat immune responses to F. pseudograminearum. The fungus F. pseudograminearum can cause the destructive disease Fusarium crown rot (FCR) of wheat, an important staple crop. Functional roles of FCR resistance genes in wheat are largely unknown. In the current research, we characterized the antifungal activity and positive-regulatory function of the cysteine-rich repeat receptor-like kinase TaCRK-7A in the defense against F. pseudograminearum in wheat. Antifungal assays showed that the purified TaCRK-7A protein inhibited the growth of F. pseudograminearum. TaCRK-7A transcript abundance was elevated after F. pseudograminearum attack and was positively related to FCR-resistance levels of wheat cultivars. Intriguingly, knocking down of TaCRK-7A transcript increased susceptibility of wheat to FCR and decreased transcript levels of defense-marker genes in wheat. Furthermore, the transcript abundances of TaCRK-7A and its modulated-defense genes were responsive to exogenous jasmonate treatment. Taken together, these results suggest that TaCRK-7A can directly inhibit F. pseudograminearum growth and mediates FCR-resistance by promoting the expression of wheat defense genes in the jasmonate pathway. Thus, TaCRK-7A is a potential gene resource in FCR-resistant wheat breeding program. [ABSTRACT FROM AUTHOR]

The article evaluates the potential for systemic infection of barley and wheat heads from soil- and seed-borne sources of inoculum, Fusarium graminearum and Fusarium pseudograminearum, in Alberta. The inoculants that are isolated from corn grain and cereal node tissue were used to study the infection from soilborne sources of inoculum. Four methods were used for the inoculation of healthy seeds to induce infection. Results show that no evidence was found for systemic infection from seed.

Homothallic Fusarium graminearum (teleomorph Gibberella zeae) and anamorphic F. culmorum are destructive pathogens causing Fusarium head blight (FHB) of small-grain cereals worldwide, while heterothallic F. pseudograminearum ( G. coronicola) seems to be restricted to Australia as a FHB pathogen. In a comprehensive treatise of pathogen population genetics, this review summarizes global knowledge of genetic diversity among isolates sampled at various spatial and temporal scales, examines the mechanisms that generate this diversity and explores the implications of pathogen diversity and plasticity to resistance breeding. Despite their different modes of reproduction, there is large variation among isolates of all three species originating from different countries and continents. With a few exceptions, haplotype diversity ranges from 60 to 100% even within populations from individual fields. In F. graminearum, over 90% of the variation is found within populations, even when samples are collected from areas as small as 0.25 m2. Variation among populations is low (4–8%) with negligible population subdivision. This indicates a high level of gene flow ( Nm = 8–71) with linkage equilibrium for the majority of selectively neutral molecular marker loci analysed. These findings for F. graminearum point to large random mating populations driven by occasional outcrossing, high gene flow across large geographical distances and a relatively low host-mediated directional selection. Similar conclusions can be drawn for the Canadian population of F. pseudograminearum, but not for populations from Australia, where different pathogen ecology may have reduced the frequency of sexual recombination. Phylogenetic analyses indicate delineation of lineages in F. graminearum, often along geographically separated lines, while the related F. pseudograminearum is a single recombining species with limited or no lineage development. The anamorphic F. culmorum shows no obvious clonal structure in its population as might have been expected. High levels of diversity within fields may have been caused by balancing selection from frequent alternation between saprophytic and parasitical life cycle and/or a hidden or recently extinct teleomorph. Other mechanisms including parasexual cycles or active transposable elements may also be involved but these have not been investigated as yet. Crosses between and among F. graminearum lineages have shown a rather simple, additive inheritance of pathogenicity and aggressiveness with frequent transgressive segregation in crosses among isolates with moderate aggressiveness. This raises the spectre of highly aggressive and/or toxigenic isolates evolving if a limited range of quantitative trait locus for FHB resistance is deployed on a large scale. Combining more than one genetically distinct sources of resistance, possibly with different modes of action against the pathogen, will be necessary to avoid severe FHB outbreaks in the future. [ABSTRACT FROM AUTHOR]

Crown rot (causal agent Fusarium pseudograminearum) is a fungal disease of major significance to wheat cultivation in Australia. A doubled haploid wheat population was produced from a cross between line ‘W21MMT70’, which displays partial seedling and adult plant (field) resistance to crown rot, and ‘Mendos’, which is moderately susceptible in seedling tests but partially resistant in field trials. Bulked segregant analysis (BSA) based on seedling trial data did not reveal markers for crown rot resistance. A framework map was produced consisting of 128 microsatellite markers, four phenotypic markers, and one sequence tagged site marker. To this map 331 previously screened AFLP markers were then added. Three quantitative trait loci (QTL) were identified with composite interval mapping across all of the three seedling trials conducted. These QTL are located on chromosomes 2B, 2D and 5D. The 2D and 5D QTL are inherited from the line ‘W21MMT70’, whereas the 2B QTL is inherited from ‘Mendos’. These loci are different from those associated with crown rot resistance in other wheat populations that have been examined, and may represent an opportunity for pyramiding QTL to provide more durable resistance to crown rot. [ABSTRACT FROM AUTHOR]

Abstract: Fusarium pseudograminearum causes crown rot of wheat in Australia and most other wheat growing regions, but its evolutionary history is largely unknown. We demonstrate for the first time that F. pseudograminearum is a single phylogenetic species without consistent lineage development across genes. Isolates of F. pseudograminearum, F. graminearum sensu lato, and F. cerealis, were collected from four countries and four single copy, nuclear genes were partially sequenced, aligned with previously published sequences of these and related species, and analysed by maximum parsimony and Bayesian inference. Evolutionary divergence varied between genes, with high phylogenetic incongruence occurring between the gene genealogies. The absence of geographic differentiation between isolates indicates that the introduction of new fungal strains to a region has the potential to introduce new pathogenic and toxigenic genes into the native population through sexual recombination. [Copyright &y& Elsevier]

This paper examines the level of pathogenic diversity in Australian Fusarium pseudograminearum and Fusarium graminearum isolates for head blight from the assessment of 51 wheat germplasm lines, barley, triticale, rye, maize and sorghum plants. A set of nine putative wheat differentials were selected and assessed with 10 F. graminearum and 12 F. pseudograminearum isolates. Isolates of both species were pathogenic on all the wheat germplasm lines, barley triticale and rye. The isolates differed largely in a quantitative way with only small differential effects and were statistically demarcated into three pathogenicity groups: low, intermediate and high. Such distribution patterns suggest that wheat germplasm lines employ different resistance mechanisms to each group of isolates and the three pathogenicity groups may have different mechanisms controlling pathogenicity. The aggressiveness of F. graminearum and F. pseudograminearum isolates on the wheat germplasm lines were marginally correlated ( r = 0.40). Durum wheats were ranked as the most susceptible while Sumai 3, Ituo Komugi, Sotome A, Sotome and Nobeokabouzu komugi were consistently grouped as resistant by both species. These findings reiterate the need to consider pathogen variability in the screening, selection and improvement of resistance to head blight in wheat. [ABSTRACT FROM AUTHOR]

Abstract: Recently the genome sequences of several filamentous fungi have become available, providing the opportunity for large-scale functional analysis including genome-wide expression analysis. We report the design and validation of the first Affymetrix GeneChip microarray based on the entire genome of a filamentous fungus, the ascomycetous plant pathogen Fusarium graminearum. To maximize the likelihood of representing all putative genes (∼14,000) on the array, two distinct sets of automatically predicted gene calls were used and integrated into the online F. graminearum Genome DataBase. From these gene sets, a subset of calls was manually annotated and a non-redundant extract of all calls together with additional EST sequences and controls were submitted for GeneChip design. Experiments were conducted to test the performance of the F. graminearum GeneChip. Hybridization experiments using genomic DNA demonstrated the usefulness of the array for experimentation with F. graminearum and at least four additional pathogenic Fusarium species. Differential transcript accumulation was detected using the F. graminearum GeneChip with treatments derived from the fungus grown in culture under three nutritional regimes and in comparison with fungal growth in infected barley. The ability to detect fungal genes in planta is surprisingly sensitive even without efforts to enrich for fungal transcripts. The Plant Expression Database (PLEXdb, http://www.plexdb.org) will be used as a public repository for raw and normalized expression data from the F. graminearum GeneChip. The F. graminearum GeneChip will help to accelerate exploration of the pathogen–host pathways that may involve interactions between pathogenicity genes in the fungus and disease response in the plant. [Copyright &y& Elsevier]

Genetic diversity within populations of Fusarium pseudograminearum isolated from wheat grains from the Canadian provinces of Alberta and Saskatchewan was investigated. Three restriction enzymes (EcoRI, HaeIII, and PstI) were used to carry out restriction analysis of the nuclear ribosomal DNA (nrDNA) intergenic spacer region (IGS region) and eight primers were used to generate inter-simple sequence-repeat (ISSR) molecular markers. Our study indicated substantially high genetic diversity within these two populations, but low genetic differentiation and frequent gene flow among populations. The IGS data showed no genetic distinction between the two Alberta populations and only minor genetic differentiation between the Saskatchewan and Alberta populations. Analysis of molecular variance indicated that most genetic variability resulted from differences among isolates within populations. Multilocus linkage disequilibrium analysis suggested a panmictic population genetic structure and the occurrence of significant recombination in F. pseudograminearum. Regular gene flow and random mating between isolates from different populations could result in novel genotypes with both improved pathological and biological traits. [ABSTRACT FROM AUTHOR]

The article assess the capability of Canadian isolates of Fusarium pseudograminearum (F. pseudograminearum), collected from seed and vegetative cereal parts and other gramineae grown in western Canada, to produce toxins in culture. F. pseudograminearum has been considered as the most important causal agent of Fusarium diseases of wheat in Australia due to its capacity to infect the head causing Fusarium head blight.

The effects of stubble management and crop rotation on suppression of soilborne pathogens was studied in wheat cropping soils taken from established trials at Moree, Warialda and Croppa Creek in northern New South Wales, Australia. Biological resilience was evaluated in two ways: by measuring severity of take-all when the pathogen ( Gaeumannomyces graminis var. tritici) was introduced to soil, and by assessing displacement of Fusarium pseudograminearum, the cause of crown rot of wheat, from buried straw pieces. No effects of stubble management or rotation with sorghum were found on suppression of either the introduced or resident pathogens at the Moree site. At Warialda and Croppa Creek, the severity of take-all in pot bioassays was significantly lower in soils from zero-tillage plots with stubble retained than in cultivated plots where the stubble was burnt. This effect was seen in soils from both continuous wheat and wheat-chickpe a rotation treatments. There were no consistent differences between treatments in soil microbial biomass or respiration, or in soil carbon contents. Stubble retention also significantly increased the rate of displacement of F. pseudograminearum from infested straw at Croppa Creek, but not at Warialda. The results showed that, at two out of three sites, retention of crop residues increased the ability of the soil to resist the effects of introduction of a major plant disease. [ABSTRACT FROM AUTHOR]

Abstract: The necrotrophic fungal pathogen Fusarium pseudograminearum (F. pseudograminearum) causes crown rot disease (CR) in wheat. This host–pathogen interaction has not been studied previously at the molecular level. In this study, using real-time quantitative PCR, the expression of 26 selected wheat genes was examined 1, 2 and 4 days after inoculation of wheat seedlings of the CR susceptible cultivar Kennedy and the partially field-resistant cultivar Sunco. Reproducible induction of eight defence genes consisting of PR1.1, PR2 (β,1‐3 glucanase), PR3 (chitinase), PR4 (wheatwin), PR5 (thaumatin-like protein), TaPERO (peroxidase), PR10 and TaGLP2a (germin-like) was observed. These genes were induced in both cultivars, however, some genes were induced more rapidly in Sunco than in Kennedy. MJ treatment also induced the above pathogen responsive defence genes in both cultivars while benzo(1,2,3)thiadiazole-7-carbothionic acid S-methyl ester (BTH) treatment weakly induced them in Kennedy only. Similarly, treatment with MJ before inoculation significantly delayed the development of necrotic symptoms for 2 weeks in both wheat cultivars, while BTH pre-treatments delayed symptom development in Kennedy only. The chemically induced protection, therefore, correlated with induction of the F. pseudograminearum-responsive genes. These results support the emerging role of jasmonate signalling in defence against necrotrophic fungal pathogens in monocots and future manipulation of this pathway may improve CR resistance in wheat. [Copyright &y& Elsevier]

Many wheat (Triticum aestivum) fields planted annually in the Pacific Northwest art infested by high populations of the lesion nematode, Pratylenchus neglectus. Spring wheat cultivars varying m tolerance and resistance to P neglectus were treated or not treated with aldicarb to examine relationships between the nematode and growth and yield of annual direct-seeded (no-till) wheat. Increasing initial density of P. neglectus in soil was more strongly associated with declining growth and yield of intolerant (Machete and Spear) than moderately tolerant (Frame and Krichauff) cultivars. Yield suppression by P. neglectus was generally 8 to 36% tot intolerant cultivars, but reached 71% in soil also harboring Heterodera avenae, Rhizoctonia solani AG-8, and Gaeumannomyces graminis vat. tritici. Intolerant cultivars had lower yields than Krichauff in rainfed but not in irrigated experiments. Density of P. neglectus in mature roots was generally lower for moderately resistant Krichauff than for susceptible Machete and Spear. Aldicarb improved yields in irrigated but not in rainfed experiments, and increased plant height and reduced variability in tiller height, canopy temperature, and density of P. neglectus in roots. This is the first report of damage to wheat by P. neglectus in the Pacific Northwest. Breeding wheat for tolerance and resistance to P. neglectus is suggested. [ABSTRACT FROM AUTHOR]

Abstract: The red pigmentation of Fusarium graminearum and related species that cause stem and head blight of cereals is due to the deposition of aurofusarin in the cell walls. To determine the importance of this polyketide for fungal physiology and pathogenicity, aurofusarin deficient mutants were produced by random and targeted mutagenesis of F. pseudograminearum and F. graminearum. We show that a gene cluster, including the F. graminearum PKS12 gene, is responsible for the biosynthesis of aurofusarin. Three F. pseudograminearum aurofusarin deficient mutants were disrupted in a region upstream from a gene with sequence homology to the aflatoxin regulatory gene aflR. Comparative PCR analyses of the aurofusarin gene cluster in F. graminearum, F. culmorum, and F. pseudograminearum show conserved organization and expression analyses detected no PKS12 transcripts in any of the mutants. To confirm that PKS12 encodes the precursor for aurofusarin, targeted mutagenesis was carried out in F. graminearum. All disruptants showed an albino phenotype. The ΔPKS12 mutants have higher growth rate and a 10-fold increase in conidia production compared to the wild type. Aurofusarin does not appear to aid in radiation protection and all the mutants are fully pathogenic on wheat and barley. HPLC analyses of aurofusarin deficient mutants confirm the absence of aurofusarin and show an increase in the level of the mycotoxin zearalenone. [Copyright &y& Elsevier]