Development Of Fungal Pathogens Research Articles

Exploring the mechanisms of endophytic bacteria for suppressing early blight disease in tomato (Solanum lycopersicum L.).

Controlling early blight of tomatoes using endophytic bacteria is an eco-friendly and sustainable approach to manage this common fungal disease caused by Alternaria solani, Alternaria alternata, and Curvularia lunata. Endophytic bacteria are microorganisms that live inside plant tissues without causing harm and can help protect the host plant from pathogens. In this work, twenty endophytic bacterial isolates from tomato healthy plants were tested against pathogenic fungal isolates that caused early blight disease in vitro. Out of the 20 tested isolates, three (B4, B7, and B17) were considered effective isolates against the growth of fungal pathogens. The three isolates were recognized as Enterobacter cloacae HS-6 (B4), Pseudomonas gessardii HS-5 (B 7), and Pseudomonas mediterranea HS-4 (B17) using 16s-rDNA sequencing. Different concentrations of bacterial cultural diltrates at 20, 40, and 60% were tested for their antagonistic effects on the development of pathogenic fungi in vitro. The lowest dry weights of pathogenic isolates in all bacterial culture filtrates were discovered at 60%. In all culture filtrates, phenolic compounds showed the largest peak area. Under greenhouse conditions, the least disease severity of tomato early blight was found for E. cloacae and its culture filtrate compared to other treatments. Real-time PCR was used to examine the expression pattern of the defense response gene β-1.3 glucanase gene in infected tomato plants with pathogenic fungi (control) as well as its relations with efficient biocontrol agent (E. cloacae). The expression of the gene increased substantially and significantly after three days from the inoculation-infected plants with C. lunata and E. cloacae while it reached the maximum after five days from the inoculation with A. alternata, A. solani and E. cloacae. Our study concluded that the endophytic bacterial isolate E. cloacae can be considered a promising biocontrol agent for preventing tomato early blight.

Effect of gaseous ozone treatment on the aroma and clove rot by Fusarium proliferatum during garlic postharvest storage

It is known that garlic bulbs preserved with traditional methods undergo considerable losses, ranging from 25 to 40%. A frequent cause of these losses is associated with the development of pathogenic fungi, such as those of the genus Fusarium. The effect of ozone on post-harvest garlic bulbs was evaluated.Garlic cloves inoculated with Fusarium proliferatum F21 and F22 strains, were exposed to a continuous gaseous ozone flow (2.14 μg m−3), during 4 days, 20 h a day. After ozone-treatment, the garlic samples were moved at 22 °C to mimic retail conditions (shelf life). The changes in several quality parameters such as fungal decay and aroma were evaluated on garlic samples, as whole bulbs, cloves with and without tunic, through a sensorial descriptive test, SPME analysis in GC/MS and microbiological approaches. The data collected showed that ozone treatment did not affect the aromatic profile of garlic. A significant detrimental effect of ozone treatment on garlic decay was observed. Our results encourage the use of gaseous ozone treatment for containing garlic fungal decay during its storage.

Effect of humidity on growth and development of fungal pathogens of ripening dates (Phoenix dactylifera L.) at Khairpur, Pakistan

Pakistan is regarded as one of the top ranked date palm cultivated regions of the world. In Sindh province of Pakistan, date palm (Phoenix dactylifera L.) is mainly cultivated in Khairpur. Date palm holds a significant position in the socio-economic development at Khairpur where several thousand peoples are associated directly or indirectly with date palm cultivation, trade and market. Date palm requires high temperature and low humidity from flowering to fruiting and no rainfall during ripening. Unfortunately, in district Khairpur, during the period of rainfall, humidity becomes very high and temperature decreases. The periods of high humidity provide favorable conditions for the growth and development of fungal pathogens which cause severe losses in yield and quality of fruits. The present study was, therefore, conducted to find out the effect of humidity on the growth and development of fungal pathogens in three cultivars of dates viz. Aseel, Kupro and Khar at ripening stage due to moisturized weather conditions at Sobho Dero Taluka of district Khairpur. The symptoms of fungal attack such as cracking, blackening, blemishes and spoilage were observed on ripened fruits. Three fungi viz. Fusarium poae, Alternaria tenuis and Aspergillus niger were isolated from infected samples of three selected cultivars. The frequencies of occurrence of these fungi were 5.66, 6.33 and 8.33 respectively. It is concluded that incidence and prevalence of fungal pathogens greatly increased during rainy season which demand stringent surveillance and control measures to minimize the damage

The Unfolded Protein Response Regulates Pathogenic Development of Ustilago maydis by Rok1-Dependent Inhibition of Mating-Type Signaling.

Fungal pathogens require the unfolded protein response (UPR) to maintain protein homeostasis of the endoplasmic reticulum (ER) during pathogenic development. In the corn smut fungus Ustilago maydis, pathogenic development is controlled by the a and b mating-type loci. The UPR is specifically activated after plant penetration and required for efficient secretion of effectors and suppression of the plant defense response. The interaction between the UPR regulator Cib1 and the central developmental regulator Clp1 modulates the pathogenic program and triggers fungal colonization of the host plant. By contrast, when activated before plant penetration, the UPR interferes with fungal virulence by reducing expression of bE and bW, the central regulators of pathogenic development encoded by the b mating-type locus. Here, we show that this inhibitory effect results from UPR-mediated suppression of the pheromone response pathway upstream of the b regulatory network. UPR activity prompts dephosphorylation of the pheromone-responsive mitogen-activated protein kinase (MAPK) Kpp2, reducing activity of the pheromone response factor Prf1 that regulates expression of bE and bW Deletion of the dual specificity phosphatase rok1 fully suppressed UPR-dependent inhibition of Kpp2 phosphorylation, formation of infectious filaments, and fungal virulence. Rok1 determines the activity of mating-type signaling pathways and thus the degree of fungal virulence. We propose that UPR-dependent regulation of Rok1 aligns ER physiology with fungal aggressiveness and effector gene expression during biotrophic growth of U. maydis in the host plant.IMPORTANCE The unfolded protein response (UPR) is crucial for endoplasmic reticulum (ER) homeostasis and disease development in fungal pathogens. In the plant-pathogenic fungus Ustilago maydis, the UPR supports fungal proliferation in planta and effector secretion for plant defense suppression. In this study, we uncovered that UPR activity, which is normally restricted to the biotrophic stage in planta, inhibits mating and the formation of infectious filaments by Rok1-dependent dephosphorylation of the pheromone responsive mitogen-activated protein kinase (MAPK) Kpp2. This observation is relevant for understanding how the fungal virulence program is regulated by cellular physiology. UPR-mediated control of mating-type signaling pathways predicts that effector gene expression and the virulence potential are controlled by ER stress levels.

Interrelations between Alien and Native Foliar Fungal Pathogens and Woody Plants in Siberia

This article presents the results of 15-year observations of alien and native foliar fungal pathogens and woody plants in Siberian arboreta and urban ecosystems and discusses the possibility of using these data to determine how the pathogenic mycobiota of woody species was formed under Siberian conditions. In total, 121 species of pathogenic micromycetes affecting the leaves of woody plants in botanical gardens and city and belonging to 2 divisions, 14 orders, and 46 genera have been revealed. Most of these species belong to the Ascomycota division (86.8%). The Basidiomycota division is represented by fungi from the order Pucciniales. Among all observed pathogens, 21 species belong to powdery mildew fungi, 15 species belong to rust fungi, and 84 species represent anamorphic fungi. A study of 108 woody plant species growing in Siberian cities has revealed 101 species of leaf pathogens, while 158 woody plant species growing in arboreta have been inhabited by 105 pathogen species. All fungal species revealed during this study, except for three species (Mycopappus alni, Venturia acerina, and Phyllosticta westendorpii), have been observed in Siberia earlier. However, some fungus–host plant associations are apparently new to science, suggesting that complexes of cryptic species differing in their host range and geographic range may occur. The main sources for tree mycobiota formation in Siberia include the invasion of pathogens together with alien plant species, the transition of pathogens from native to alien plant species, the enhancement of a pathogenicity of saprotrophic fungi, and the expansion of fungi onto new hosts. The majority of pathogens (65−75% of the total number of revealed fungi) locate on native plants. Alien plants are infected mainly by (native) pathogens. Only eight pathogen species have been introduced in Siberia with alien plants; three of them originate from the Far East (Cercospora gotoana, Phyllosticta phellodendricola, and Erysiphe palczewskii), while five are of European origin (Cladosporium syringae, Phyllosticta vincae-minoris, Erysiphe syringae, Erysiphe alphitoides, and Erysiphe berberidis). In Siberia, the lateness of phenological phases of plants originating from mild climatic zones, may be favorable for the development of fungal pathogens, such as Erysiphe alphitoides, causing the powdery mildew of oak trees.

Influence of Cultivars and Seed Thermal Treatment on the Development of Fungal Pathogens in Carrot and Onion Plants

Carrot and onion are vegetables representing an important segment of fresh market. They suffer from serious fungal diseases that can inflict great damage on crops, i.e. alternaria leaf blight, peronospora downy mildew, and botrytis neck rot. The resistance of selected carrot and onion cultivars important for the production of vegetables in the Czech Republic was tested by exposure to targeted infection by the above fungal pathogens. The exposure of eleven carrot cultivars to spores of Alternaria dauci showed that the most resistant and sensitive cultivars were Katrin, Cortina F1, Afalon F1 and Favorit, Tinga, Berlika F1, respectively. A targeted infection of onion cultivars with Botrytis aclada clustered them into three groups: Amfora F1, Bolero, Tosca, Triumf F1 (strong resistance), Avalon, Grenada (medium resistance), Alice, Karmen, Všetana (low resistance). Similar groups were distinguished also after the infection with Peronospora destructor: Avalon, Bolero, Tosca (strong resistance), Alice, Amfora F1, Grenada, Karmen, Triumf F1 (medium resistance),Všetana (low resistance). Hot water treatment of carrot seeds applied after the inoculation with A. dauci decreased the development of the infection 1.3-2.3-fold, whereas the protective effect observed with onion seeds against the infection by P. destructor and B. aclada was lower.

Conservação de manga com uso de fécula de mandioca preparada com extrato de cravo e canela

O objetivo deste trabalho foi avaliar a conservação pós-colheita de mangas 'Palmer' e o desenvolvimento de fungos fitopatogênicos nos frutos, após o revestimento por fécula de mandioca, preparada com águas de cravo e de canela. Para execução do trabalho, foram utilizados cinco tratamentos: T1= testemunha (sem revestimento), T2= imersão em solução de fécula a 3%, preparada com água de cravo, por 12 horas, T3= imersão em solução de fécula a 3%, preparada com água de canela, por 12 horas, T4= imersão em solução de fécula a 3%, preparada com água destilada, T5= imersão em solução de fécula a 3%, preparada com água de canela, por 24 horas e T6= imersão em solução de fécula a 3%, preparada com água de cravo, por 24 horas. Esses frutos foram armazenados em câmara a 25 ºC, por dez dias. Foram avaliados perda de matéria fresca, firmeza, cores interna e externa, pH, sólidos solúveis, ácido ascórbico, acidez titulável e identificação de patógenos presentes nas lesões. O revestimento de mangas 'Palmer' por fécula de mandioca, preparada com águas de cravo ou de canela, não influenciou na maioria das características de pós-colheita avaliadas. Entretanto, o revestimento assim preparado reduz a percentagem de fitopatógenos durante o armazenamento, sendo o extrato de cravo mais eficiente que o extrato de canela.

New wind in the sails: improving the agronomic value of crop plants through RNAi-mediated gene silencing.

RNA interference (RNAi) has emerged as a powerful genetic tool for scientific research over the past several years. It has been utilized not only in fundamental research for the assessment of gene function, but also in various fields of applied research, such as human and veterinary medicine and agriculture. In plants, RNAi strategies have the potential to allow manipulation of various aspects of food quality and nutritional content. In addition, the demonstration that agricultural pests, such as insects and nematodes, can be killed by exogenously supplied RNAi targeting their essential genes has raised the possibility that plant predation can be controlled by lethal RNAi signals generated in planta. Indeed, recent evidence argues that this strategy, called host-induced gene silencing (HIGS), is effective against sucking insects and nematodes; it also has been shown to compromise the growth and development of pathogenic fungi, as well as bacteria and viruses, on their plant hosts. Here, we review recent studies that reveal the enormous potential RNAi strategies hold not only for improving the nutritive value and safety of the food supply, but also for providing an environmentally friendly mechanism for plant protection.

The effect of S-(ferrocenylmethyl)-thiosalicylic acid sodium salt on the germination and growth of cereal grains and seedlings and on the development of pathogenic fungi

The sodium salt of S-(ferrocenylmethyl)-thiosalicylic acid was studied in the context of its possible use as a systemic fungicide and, concurrently, as a source of physiologically active iron fur crop plants. It was found that this metallocene was taken up by maize seedlings growing in liquid mediums, and used for chlorophyll synthesis, in a concentration range as low as 0.05-0.08 mM dm<sup>-3</sup>. In the concentration range of 0.05-1.5 mM dm<sup>-3</sup>, it inhibited germination, seedling growth and Y-amylase activity while it stimulated the activities of proteinases, catalase and peroxidase. When sprayed on cereal leaves at a concentration of 1.0-2.0 mM dm<sup>-3</sup>, it exhibited fungicidal properties: inhibition of fungus development without harming cereal plant leaves and stimulated chlorophyll synthesis.

Growth inhibition of an Araucaria angustifolia (Coniferopsida) fungal seed pathogen, Neofusicoccum parvum, by soil streptomycetes

BackgroundAraucariaceae are important forest trees of the southern hemisphere. Life expectancy of their seedlings can largely be reduced by fungal infections. In this study we have isolated and characterized such a fungus and investigated the potential of Streptomyces Actinobacteria from the respective rhizosphere to act as antagonists.ResultsThe pathogenic fungus from Araucaria angustifolia seeds was identified by morphological markers (pore-associated Woronin-bodies) as belonging to the Pezizomycotina. Molecular data identified the fungus as Neofusicoccum parvum (Botryosphaeriaceae). Co-cultures on agar of this fungus with certain streptomycete isolates from the rhizosphere, and from the surface of Araucaria roots significantly reduced the growth of the fungus. HPLC analysis of the agar yielded streptomycete-specific exudate compounds which were partly identified. There were differences in compounds between single (bacteria, fungus) and dual cultures (bacteria + fungus).ConclusionStreptomycetes from the rhizosphere of Araucariaceae produce exudates which can suppress the development of pathogenic fungi in their seeds.

Antifungal effects of iron sulfate on grapevine fungal pathogens

The present study aimed to determine the most efficient experimental conditions of iron sulfate use leading to optimal inhibition in the development of fungal pathogens. Assays have been focused on fungal species inducing severe grapevine diseases. FeSO 4 directly inhibited the in vitro mycelial growth of Botrytis cinerea, Eutypa lata, Phaeomoniella chlamydospora, Phaeoacremonium aleophilum, Diplodia seriata, and Neofusicoccum parvum with variable efficiency in the range of 0.5–10 mM. The development was always completely inhibited at 20 mM. This inhibitory effect was greatly increased at acidic pH values. The anionic moiety of the molecule was of importance since bromide, chloride and sulfate were highly active, whereas acetate and oxalate showed a small effect. Electron microscope observations on E. lata and B. cinerea showed that a treatment with FeSO 4 induced dramatic changes in the hyphal organization leading to cell death. No toxicity was observed on grapevine leaves following repeated FeSO 4 sprays in the antifungal concentration range. Therefore, FeSO 4 may be proposed to effectively replace the long-term pollutant use of CuSO 4 as an antifungal agent, with the additional advantage of iron being an important plant micronutrient.

Identification and characterization of a class III chitin synthase gene of Moniliophthora perniciosa, the fungus that causes witches’ broom disease of cacao

Chitin synthase (CHS) is a glucosyltransferase that converts UDP-N-acetylglucosamine into chitin, one of the main components of fungal cell wall. Class III chitin synthases act directly in the formation of the cell wall. They catalyze the conversion of the immediate precursor of chitin and are responsible for the majority of chitin synthesis in fungi. As such, they are highly specific molecular targets for drugs that can inhibit the growth and development of fungal pathogens. In this work, we have identified and characterized a chitin synthase gene of Moniliophthora perniciosa (Mopchs) by primer walking. The complete gene sequence is 3,443 bp, interrupted by 13 small introns, and comprises a cDNA with an ORF with 2,739 bp, whose terminal region was experimentally determined, encoding a protein with 913 aa that harbors all the motifs and domains typically found in class III chitin synthases. This is the first report on the characterization of a chitin synthase gene, its mature transcription product, and its putative protein in basidioma and secondary mycelium stages of M. perniciosa, a basidiomycotan fungus that causes witches' broom disease of cacao.

Incidence of potentially toxigenic fungi in maize (Zea mays L.) grain used as food and animal feed

Recently, new maize hybrids have been introduced in northern Mexico to reduce importations of grain, which is mainly directed for the production of flour and animal feed. This represents a potential risk to both human and animal health because of the development of fungal pathogens under the local weather conditions; thus, the identification of tolerant hybrids has become a priority. In this way, the objective of this study was to observe the mycoflora development in maize. There were 12 yellow and 10 white seed maize hybrids randomly planted. At harvest time, a grain sample of each plot was collected, surface-sterilized, plated in culture media, and incubated. After 7 days, colonies were observed and analyzed. The major fungi encountered were Fusarium spp., Penicillium spp., and Aspergillus spp. When compared with the yellow hybrids, white hybrids had 34, 52 and 22% less infection by F. verticillioides, Aspergillus flavus, and Aspergillus niger, respectively, and almost the double infection with Penicillium spp. White hybrids presented 51% more healthy grains than the yellow hybrids.

A Pattern Recognition Tool for Quantitative Analysis of In Planta Hyphal Growth of Powdery Mildew Fungi

The development of fungal pathogens can be quantified easily at the level of spore germination or penetration. However, the exact quantification of hyphal growth rates after initial, successful host invasion is much more difficult. Here, we report on the development of a new pattern recognition software (HyphArea) for automated quantitative analysis of hyphal growth rates of powdery mildew fungi on plant surfaces that usually represent highly irregular and noisy image backgrounds. By using HyphArea, we measured growth rates of colonies of the barley powdery mildew, Blumeria graminis f. sp. hordei, on susceptible and induced-resistant host plants. Hyphal growth was not influenced by the resistance state of the plants up to 48 h postinoculation. At later time points, growth rate increased on susceptible plants, whereas it remained restricted on induced-resistant plants. This difference in hyphal growth rate was accompanied by lack of secondary haustoria formation on induced-resistant plants, suggesting that induced resistance in barley against Blumeria graminis is caused mainly by reduced penetration rates of primary as well as secondary appressoria leading, finally, to fewer and less-developed fungal colonies. No evidence was found for reduced nutrient-uptake efficiency of the primary haustoria in induced-resistant leaves, which would be expected to have resulted in reduced hyphal growth rates during the first 48 h of the interaction.

A mitogen-activated protein kinase pathway modulates the expression of two cellulase genes in Cochliobolus heterostrophus during plant infection.

Conserved eukaryotic signaling elements play an important role in the development of fungal pathogens on their hosts. Chk1, a mitogen-activated protein kinase (MAPK), functions in virulence, mating, and sporulation of the maize leaf pathogen Cochliobolus heterostrophus. Suppression subtractive hybridization was used to identify fungal genes whose expression on the host plant is affected in chk1 deletion mutants. Two of the genes isolated in this screen were predicted to encode cellulolytic enzymes: a cellobiohydrolase, CBH7, and an endoglucanase, EG6. Expression of EG6 and CBH7 was followed by the fusion of their upstream regulatory regions to the coding sequence of the green fluorescent protein. Induction of both genes began at the onset of invasive growth and reached its maximal extent during leaf necrosis. Furthermore, EG6 was induced preferentially within necrotic lesions. Disruption of MAPK CHK1 resulted in a delay in the penetration of hyphae into the leaf and a concomitant delay in the induction of expression of both cellulase genes. In saprophytic culture, the absence of Chk1 resulted in a marked delay in the induction of CBH7 expression by crystalline cellulose. EG6 was expressed at a basal level in culture, and this expression was found to depend strictly on Chk1. Thus, the Chk1 MAPK signaling pathway is involved in the regulation of two cellulase-encoding genes and is necessary for their timely induction by environmental signals.

Effect of aqueous extracts of aspen, black currant, folded blackberry and walnut leaves on development of pathogenic fungi

The antifungal activity of water extracts of dried leaves of folded blackberry (Rubus plicatus W. et N.), walnut (Juglans regia L.), black currant (Ribes nigrum L.), and aspen (Populus tremula L.) was assessed in the in vitro experiment. The tested fungi were Alternaria alternata, Botrytis cinerea, Rhizoctonia solani, Fusarium culmorum, F. oxysporum and F. solani. It was found that all tested extracts inhibited the development of A. alternaria and F. oxysporum, whereas the strongest inhibiting effect was exhibited by extracts of aspen (A. alternata and F. oxysporum), black current (A. alternata) and folded blackberry (F. oxysporum). The tested extracts had no effect on B. cinerea.

Genetic engineering of plants to enhance resistance to fungal pathogens—a review of progress and future prospects

Recent applications of techniques in plant molecular biology and biotechnology to the study of host–pathogen interactions have resulted in the identification and cloning of numerous genes involved in the defense responses of plants following pathogen infection. These include: genes that express proteins, peptides, or antimicrobial compounds that are directly toxic to pathogens or that reduce their growth in situ; gene products that directly inhibit pathogen virulence products or enhance plant structural defense genes, that directly or indirectly activate general plant defense responses; and resistance genes involved in the hypersensitive response and in the interactions with avirulence factors. The introduction and expression of these genes, as well as of antimicrobial genes from nonplant sources, in a range of transgenic plant species have shown that the development of fungal pathogens can be significantly reduced. The extent of disease reduction varies with the strategy employed as well as with the characteristics of the fungal pathogen, and disease control has never been complete. Manipulation of salicylic acid, ethylene, and cytokinin levels in transgenic plants have provided some interesting results with regard to enhanced disease tolerance or susceptibility. The complex interactions among the expressed gene product, plant species, and fungal pathogen indicate that the response of transgenic plants cannot be readily predicted. Combinations of defense gene products have shown considerably more promise in reducing disease than single-transgene introductions. The use of tissue-specific or pathogen-inducible promoters, and the engineered expression of resistance genes, synthetic antimicrobial peptides, and elicitor molecules that induce defense responses have the potential to provide commercially useful broad-spectrum disease resistance in the not-too-distant future. The issues and challenges that will need to be addressed prior to the widespread utilization of these transgenic plants are highlighted.