Fusarium oxysporum

Calli of carnation (Dianthus caryophyllus, L.) cv. Pallas resistant and susceptible to Fusarium oxysporum f.sp. dianthi races 1 and 8 were exposed to fungal mycelia for 24, 48 and 72 h. The ultrastructure of the cells from carnation calli was studied by transmission electron microscopy. Fungal chitin and plant and fungal callose were detected using coloidal gold complexed to lectin wheat germ agglutinin and commercial monoclonal antibodies, (1 4 3)-β-glucan, and standard electron microscopy and cryoultramicrotomy. This study provides evidence that during the incompatible reaction, proximal and uninvaded Pallas cells delayed fungal growth with newly formed callose barriers that plugged plasmodesmata, coated cells or formed a tylose-like structure. The plant strategy induced by race 8 in Pallas was less successful with the loosening of host cell walls and the earlier penetration of the pathogen. This study showed that Pallas cells did not induce alterations in hyphal cells for either interaction. The combination of fungus-infected carnation calli and gold cytochemistry facilitates the study of race-specific early plant defense reactions.

The cellular and molecular events associated with cell death during compatible interaction between Fusarium oxysporum sp. linii and a susceptible flax (Linum usitatissimum) cell suspension are reported here. In order to determine the physiological and molecular sequence of cell death of inoculated cells, reactive oxygen species (ROS) production, mitochondrial potential, lipoxygenase, DNase, protease and caspase-3-like activities, lipid peroxidation and secondary metabolite production were monitored. We also used microscopy, in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and DNA fragmentation assay. Cell death was associated with specific morphological and biochemical changes that are generally noticed in hypersensitive (incompatible) reaction. An oxidative burst as well as a loss of mitochondrial potential of inoculated cells, an activation of lipoxygenase and lipid peroxidation were noted. Enzyme-mediated nuclear DNA degradation was detectable but oligonucleosomal fragmentation was not observed. Caspase-3-like activity was dramatically increased in inoculated cells. Phenylpropanoid metabolism was also affected as demonstrated by activation of PAL and PCBER gene expressions and reduced soluble lignan and neolignan contents. These results obtained in flax suggest that compatible interaction triggers a cell death sequence sharing a number of common features with the hypersensitive response observed in incompatible interaction and in animal apoptosis.

Drought can negatively impact pod production despite the fact that cacao production usually occurs in tropical areas having high rainfall. Polyamines (PAs) have been associated with the response of plants to drought in addition to their roles in responses to many other stresses. The constitutive and drought inducible expression patterns of genes encoding enzymes involved in PA biosynthesis were determined: an ornithine decarboxylase (TcODC ), an arginine decarboxylase (TcADC ), an S-adenosylmethionine decarboxylase (TcSAMDC ), a spermidine synthase (TcSPDS ), and a spermine synthase (TcSPMS ). Expression analysis using quantitative real-time reverse transcription-PCR (QPCR) results showed that the PA biosynthesis genes were expressed in all plant tissues examined. Constitutive expression of PA biosynthesis genes was generally highest in mature leaves and open flowers. Expression of TcODC, TcADC, and TcSAMDC was induced with the onset of drought and correlated with changes in stomatal conductance, photosynthesis, photosystem II efficiency, leaf water potential and altered emission of blue-green fluorescence from cacao leaves. Induction of TcSAMDC in leaves was most closely correlated with changes in water potential. The earliest measured responses to drought were enhanced expression of TcADC and TcSAMDC in roots along with decreases in stomatal conductance, photosynthesis, and photosystem II efficiency. Elevated levels of putrescine, spermidine, and spermine were detected in cacao leaves 13 days after the onset of drought. Expression of all five PA associated transcripts was enhanced (1.5e3-fold) in response to treatment with abscisic acid. TcODC and TcADC, were also responsive to mechanical wounding, infection by Phytophthora megakarya (a causal agent of black pod disease in cacao), the necrosis-and ethylene-inducing protein (Nep1) of Fusarium oxysporum, and flower abscission. TcSAMDC expression was responsive to all stresses except flower abscission. TcODC, although constitutively expressed at much lower levels than TcADC, TcSAMDC, TcSPDS, and TcSPMS, was highly inducible by the fungal protein Nep1 (135-fold) and the cacao pathogen Phytophthora megakarya (671-fold). The full length cDNA for ODC was cloned and characterized. Among the genes studied, TcODC, TcADC, and TcSAMDC were most sensitive to induction by drought in addition to other abiotic and biotic stresses. TcODC, TcADC, and TcSAMDC may share signal transduction pathways and/or the stress induced signal induction pathways may converge at these three genes leading to similar although not identical patterns of expression. It is possible altering PA levels in cacao will result in enhanced tolerance to multiple stresses including drought and disease as has been demonstrated in other crops. Published by Elsevier Masson SAS.

This monograph covers history and nomenclature of the Genus Fusarium, Fusarium nomenclature, classification of the genus Fusarium (the Wollenbecher  and Reinking classification of Fusarium genus (1935), the  Snyder and Hansen classification, 1940, the A. Raillo classification, 1950,  the W. Gerlach & H.I. Nierenberg classification, 1982m the C. Booth classification, 1971, the John F. Leslie, Brett A. Summerell classification,  the toxigenic Fusarium species ), distribution and diversity of Fusarium species, the Fusarium morphology, Fusarium genomics, Fusarium diseases in plants, man and animals, isolation and identification of Fusarium species , with special emphasis on description of Fusarium species, Fusarium books  and some research projects

Long noncoding RNAs (lncRNAs) play important roles in abiotic and biotic stress responses; however, studies on the mechanism of regulation of lncRNA expression are limited in plants. The present study examined the relationship between lncRNA expression level and two active histone modifications (H3K4me3 and H3K36me3) in Brassica rapa. Both histone marks were enriched in the chromatin regions encoding lncRNAs, especially around the transcription start site. The transcription level of long intergenic noncoding RNAs was positively associated with the level of H3K4me3 and H3K36me3, while this association was not observed in natural antisense RNAs (NATs) and intronic noncoding RNAs. As coordinate expression of mRNAs and paired NATs under biotic stress treatment has been identified, the transcriptional relationship between mRNAs and their paired NATs following Fusarium oxysporum f. sp. conglutinans (Foc) inoculation was examined. A positive association of expression levels between mRNAs and their paired NATs following Foc inoculation was observed. This association held for several defense-response-related genes and their NAT pairs. These results suggest that coordinate expression of mRNAs and paired NATs plays a role in the defense response against Foc.

The Trichoderma based emulsifiable mycofungicide for controlling foliar dis¬eases lessened the yield loss to economically acceptable level with significant increase of the quality of product. The amount of phylloplane originated T. harzianum and T. parceramosum strains containing liquid formulation, to be applied as leaf spray, might be reduced in two order of magnitud as compared to the solid preparations to achieve the same effect. Both sensitivity of 13 phytopathogenic fungi to antifungal properties of toxic substances released by 32 Trichoderma strains and their susceptibilty to the same were examined during development of new mycofungicide. Both toxin production of Trichodermas and the sensitivity of target fungi varied within large limits, being Pythium irregulare the most, while Phytophthora infestans and Macrophomina phaseolina the less tolerant. The sensitivity responses of fungi to toxins correlated to their susceptibility to antagonists. The spectrum of antagonists of pathogenic fungus or targets of Trichoderma strain proved to be unpredictable. Conidia of Trichoderma strains in liquid paraffin (LP) of pharmaceutical quality (LP PQ) survived over 2 years. However, in commercial LP the survival of them significantly decreased in strain dependent manner, and the presence of emulsifiers selectively reduced the survival rate as well. The LP PQ was not phytotoxic in therapeutic doses, but commercial LP proved to be toxic when applied as leaf spray independently on the emulsifiers. Both fungitoxic and phytotoxic contaminants of commercial LP could be eliminated with activated carbon.
Oros, G. and Naár, Z. (2017) Mycofungicide: Trichoderma Based Preparation for Foliar Applications. Ameri¬can Journal of Plant Sciences, 8, 113-125. http://dx.doi.org/10.4236/ajps.2017.82009 [ID: 2602975]